Research ArticleOrganic Gas and Element Geochemistry of HydrothermalFluids of the Newly Discovered Extensive Hydrothermal Area inthe Wallis and Futuna Region (SW Pacific)
C Konn 1 J P Donval1 V Guyader1 E Roussel2 E Fourreacute3 P Jean-Baptiste3
E Pelleter1 J L Charlou1 and Y Fouquet1
1 Ifremer Laboratoire des Cycles Geochimiques et Ressources CS10070 29280 Plouzane France2Ifremer Laboratoire de Microbiologie des Environnements Extremes CS10070 29280 Plouzane France3LSCE UMR 8212 CEA-CNRS-UVSQ 91191 Gif-sur-Yvette France
Correspondence should be addressed to C Konn cecilekonnifremerfr
Received 23 June 2017 Revised 31 October 2017 Accepted 17 December 2017 Published 11 March 2018
Academic Editor Xing Ding
Copyright copy 2018 C Konn et alThis is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
Two newly discovered hydrothermal vent fields of the Wallis and Futuna region Kulo Lasi and Fatu Kapa were sampled for fluidgeochemistry A great geochemical diversity was observed and assigned to the diversity of lithologies as well as the occurrenceof various processes Kulo Lasi fluids likely formed by interaction with fresh volcanic rocks phase separation and mixing withmagmatic fluid Conversely the geochemistry of the Fatu Kapa fluids would be mostly due to waterfelsic lavas reactions In termsof organic geochemistry fluids from both fields were found to be enriched in formate acetate and semivolatile organic compounds(SVOCs) n-alkanes n-fatty acids and polyaromatic hydrocarbons (PAHs) Concentrations of SVOCs reached a few ppb at mostThe distribution patterns of SVOCs indicated that several processes and sources at once of biogenic thermogenic and abiogenictypes likely controlled organic geochemistry Although the contribution of each process remains unknown the mere presenceof organics at the 120583M level has strong implications for metal dispersion (cycles) deposition (ore-forming) and bioavailability(ecosystems) especially as our fluxes estimations suggest that back-arc hosted vent fields could contribute as much as MOR to theglobal ocean heat and mass budget
1 Introduction
Although back-arc settings are favourable environments forthe formation of hydrothermal convection cells hydrother-mal exploration has long been conducted to a greater extentonMid-Oceanic Ridges (MOR) Today more than 600 activehydrothermal vent fields have been discovered and abouthalf of them are located at MOR against a fifth in back-arc basins (BAB) [1] Yet back-arc environments are likelyto generate more diversity than their MOR homologs interms of fluid chemistry because of the variety of lithologiesthe fluids can react with (eg basaltic to rhyolitic volcanicrocks with or without arc-like geochemical signature variousalteration mineralogical assemblages) as well as the possiblecontribution of magmatic-related aqueous fluids [2ndash5] TheWallis and Futuna area was surveyed for hydrothermal
activity because of its very peculiar geological settings withina back-arc system and its potential relevance for mineralresources [6 7] It is located about 200 km west of thenorthern tip of the Tonga-Kermadec trench where the fastestsubduction rates have been recorded (18 to 24 cm per year)and occur at the junction of 2 BAB the Lau and the North-Fiji BAB [8] Here we report on the geochemistry of the fluidsof the very first two vent fields discovered in the area and inthis type of environment We chose to bring a special focuson organic geochemistry because it has been hardly studiedin modern hydrothermal systems despite the recent growinginterest for organic matter (OM) in the oceanThe discussionfocuses on processes controlling the geochemistry as well asimplications of the presence of organic molecules at the localand regional scales
HindawiGeofluidsVolume 2018 Article ID 7692839 25 pageshttpsdoiorg10115520187692839
2 Geofluids
Organic geochemistry of hydrothermal fluids has gen-erally been far less studied than the mineral and gas geo-chemistry In most cases works focused on small molecules(hydrocarbon gases volatile fatty acids and amino acids)and very few data are available on semivolatile organiccompounds (SVOCs) Despite the growing interest for OM inthe ocean and hydrothermal systems there is still a major lackin identification and quantification of organic compounds[10ndash15] Notably numbers of studies agree on the majorligand role of organics in metal stabilisation transportationbioavailability and ore-forming but there are hardly any clueson the nature of these ligands in hydrothermal environments[16ndash25] Organic compounds in hydrothermal fluids maycome frommarine dissolved organicmatter (DOM) recycling[12 13] subsurface biomass degradation [26] entrainment oforganic detritus from local recharge zones and subsequentdegradation or abiotic formation in the deep subsurface[27ndash30] The latter is supported by many theoretical [31ndash33] and experimental work summarised in two reviews [3435] Conversely some other studies reported the absence oforganic compounds in hydrothermal fluids except at the LostCity alkaline vent field which is theoretically more favourablefor abiotic synthesis [36] Nevertheless we report here thepresence of semivolatile organic compounds in hydrother-mal fluids from the Wallis and Futuna area and provideconcentrations of a selection of extractable compounds thathave been identified elsewhere as hydrothermally derived[27 37] n-alkanes n-fatty acids (n-FAs) mono- and pol-yaromatic hydrocarbons (BTEXs and PAHs) These very firstquantitative field data might feed thermodynamic models ofabiotic synthesis guide the design of experiments to betterunderstand hydrothermal organic geochemistry and helpassessing the importance of hydrothermally derived organiccompounds in metal complexation and as a nutrient formicroorganisms complete fluxes calculation and enter in thecarbon cycle budget calculations
2 Geological Settings
Wallis and Futuna Islands are located at the transitionbetween the North Fiji and the Lau back-arc basins Thisgeodynamical setting accounts for complex volcanic andtectonic activity in the area Pelletier et al [38] and Fouquetet al [6] observedmultiple active extensional zones includingwidespread areas composed of numerous individual volca-noes (eg Southeast Futuna volcanic zone (SEVZ)) and wellorganised spreading centers such as the Futuna and Alofioceanic ridge West of Futuna Island the 20ndash30∘ trendingFutuna spreading center (FSC) is composed of a series of enechelon spreading segmentsThe opening rate of this oceanicridge has been estimated at 4 cmyr from the interpretationof magnetic anomalies [38] East and southeast of FutunaIsland bathymetric maps and reflectivity data clearly revealthat active extension and recent volcanism occur in the SEVZas well as along the Alofi spreading center [6] The SEVZ is abroad zone of diffuse volcanism bordered by the ENE-WSWtrending volcanic graben (named Tasi Tulo graben) to thenorth and the NNE-SSW trending Alofi spreading center to
the south The SEVZ includes Kulo Lasi active volcano theFatu Kapa and Tasi Tulo volcanic zones ([7] Figure 1)
Fluids were sampled at the Kulo Lasi and Fatu Kapa sitesKulo Lasi has been described in detail by Fouquet and collab-orators [39] In summary it is a shield volcano located about100 km southeast of Futuna Island (Figure 1) It representsthe most recent volcano in the SEVZ and is composed ofbasaltic to trachy-andesitic lava with no direct geochemicalaffinity with subduction [39]The volcanic edifice is ca 20 kmin diameter and appears relatively flat with the top located ata depth of 1200m and the base only 300m deeper (ca 1500mbelow sea level) It exhibits a central caldera (5 km in diameterand 200ndash300m deep) with a flat bottom covered by recentlavas and a central mound composed of older and tectonisedlava flow By contrast the Fatu Kapa volcanic area is in a20 km wide transition zone between the Tasi Tulo grabenand the Kulo Lasi volcano Here only small (lt1 km) volcanicedifices are seen to be consisting of youngmafic to felsic lavas(Figure 1)
3 Sampling and Analytical Procedures
Sampling was achieved at Kulo Lasi and Fatu Kapa bythe HOV Nautile during the FUTUNA 1 and FUTUNA3 cruises conducted by Ifremer in 2010 and 2012 Fluidsamples were taken at the nose of smokers to minimiseseawater contamination Samples of volumes up to 750mL ofhydrothermal fluids were collected in titanium syringes thatwere modified after the model described in Von Damm et al[40]The gas-tightness was greatly improved and ensured themajority of the gas to be recoveredThose same syringes havebeen used in several studies by Charlou et al and have showngood results notably for gas-Mg correlations (eg Charlouet al 2002) Autonomous temperature sensors (S2T 6000-DH NKE Instrumentation) were mounted on the samplernozzle As soon as the fluids were recovered pH H2S andClminus concentrations were measured to evaluate the qualityof the sample Total gases were immediately extracted andanalysed then aliquots of gas were conditioned for furtherstable isotopes measurements Finally the gas-free fluid wasconditioned for major and minor elements analyses on theone hand and for organic compounds analyses on the otherhand
31 Gas Extraction and Analyses Total gas was extracted asdescribed in Charlou and Donval [41] Preliminary majorgases (CO2 H2 CH4 and N2) concentrations were obtainedon board by using a portable chromatograph (MicrosensorTechnology Instruments Inc) that was mounted on linewith the gas extractor Extracted gases were conditionedon board in stainless steel pressure-tight flasks and storeduntil analyses Gases were separated byGas-Chromatography(Agilent GC 7890A Agilent Technologies) and quantitativelyanalysed by triple detection using mass (MS 5975C Agilenttechnologies) flame ionisation and thermal conductivitydetectors Aliquots of gas were stored both in vacuum tighttubes (Labco Ltd) and in copper tubes to be sent for furthercarbon isotope analyses (Isolab bv Netherlands) and Heisotopes analyses (CEA Saclay France) respectively
Geofluids 3
Figure 1 Bathymetric map of the study area Close-ups of Fatu Kapa and Kulo Lasi are shown in boxes where sample positions are markedwith red disks Copyrights from Ifremer FUTUNA 1 2 and 3 cruises
32 Inorganic Geochemistry Sample Preparation and Anal-yses pH was measured using a combined glass electrode(Ecotrode Plus Metrohm) Clminus and H2S were measured bypotentiometry using AgNO3 (005M) and HgCl2 (001M) astitrating solutions respectivelyNaOH (2M)was added to thealiquot before H2S measurement SO4 Br Na K Mg Ca Liand Cl were measured by ionic chromatography (Dionex IonChromatograph System 2000) after appropriate dilutions FeMn Cu Zn Sr Li and Rb were measured by flame atomicabsorption spectrometry using standard additions (AAnalystPerkin Elmer Inc) Aliquots for silica determination wereimmediately diluted 100- to 200-fold and analysed by thesilicomolybdate automatic colorimetric method [42 43]
33 Organic Geochemistry Total Organic Carbon (TOC)was measured using a multi NC 3100 (Analytik Jena AGGermany) Samples were acidified online with HCl and thenpurged with O2 to remove inorganic carbon (IC) A TIC
control analysis was performed and followed by three TOCmeasurements on each sample
Acetate and formate concentrations were determinedusing a Dionex ICS-2000 Reagent-Free Ion Chromatogra-phy System equipped with an AS50 autosampler (DionexCamberley UK) Chromatographic separationwas conductedusing two Ionpac AS15 columns in series at 30∘C and thedetermination of species was carried out using an AnionSelf-Regenerating Suppressor (ASRS 300 4mm) unit in com-bination with a DS6 heated conductivity cell (35∘C) Thegradient program was as follows 6mmol Lminus1 KOH (43min)increase from 27mmol Lminus1 KOH minminus1 to 60mmol Lminus1(39min) decrease from 54mmol Lminus1 KOHminminus1 to 6mmolLminus1 (5min)
SVOCs were extracted using Stir Bar Sorptive Extraction(SBSE) Basically any compound with a log Kow gt 25 isrecovered with a rate gt 50 [44] The method was improvedafter Konn et al [37] The entire content of the titanium
4 Geofluids
Table 1 Main GC analytical parameters used for calibration and analyses of hydrothermal fluid samples Each group of compounds (n-alkanes BTEXs PAHs and n-fatty acids) was analysed using separate twisters
n-Alkanes BTEX amp PAHs n-Fatty acidsOvenInitial 119879 (∘C) 40 40 40Initial 119905 (min) 1 1 1ramp 40 to 320∘C at 12∘Cmin 40 to 320∘C at 12∘Cmin 40 to 320∘C at 20∘CminFinal 119879 (∘C) 320 320 320Final 119905 (min) 2 2 2Injector119879 (∘C) 250 250 325
Table 2 Experimental conditions used for calibration curves Linear regressions were performed on one order of magnitude concentrationdomain depending on the concentration range of the samples
syringe was transferred into a precombusted glass bottle andsix 90mL aliquots of the sample were poured into 100mLprecombusted glass vials 10mL ofMeOHwas added to avoidadsorption of the compounds onto the wall of the vialsInternal standards were added to the solutions in 2012 so thatquantification could only be achieved in Fatu Kapa fluidsExtraction was performed in sealed vials with ultrainertseptum crimps at 300 rpm and using 48 120583L PDMS Twisters(Gerstel GmbH) We focused on a selection of chemicalgroups that had previously been described as hydrothermallyderived [27] To that respect pairs of aliquots were dedicatedto analysis of n-alkanes n-FAs and both BTEXs and PAHsrespectively Extraction kinetics experiments showed thatchemical equilibrium was reached after 5 h of extraction forn-alkanes 4 h for PAHs and 14 h for n-FAs (Konn unpub-lished results) Twisters were then removed rinsed with MQwater dried and stored at +4∘C until analyses by ThermalDesorption-Gas Chromatography-Mass Spectrometry (TD-GC-MS) [37] Analytical parameters were adjusted for eachgroup of compounds (Table 1)
For each batch of conditioned Twisters one was sparedstored at +4∘C and analysed in the same run as the otherTwistersThis dry blank aimed at showing any contaminationthat could have occurred during conditioning storage andtransport MQ water samples were prepared and extractedon board as regular hydrothermal samples to check if anycontaminations could have occurred during the samplepreparation step Deep-sea water was also collected pro-cessed and analysed using the same titanium syringes andaccording to the same protocols as for hydrothermal fluidsamples and thus constitute the reference blank experiment
Calibration was achieved using a commercial stan-dard solution of BTEXs and 3 custom standard solu-tions of C9ndashC20 n-alkanes C6ndashC18 n-FAs and PAHs con-taining naphthalene (N) Acenaphtene (A) Fluorene (F)Phenanthrene (Ph) Anthracene (An) Fluoranthene (Fl)and pyrene (Py) (LGC Standards LGC Ltd) Deuteratedn-alkanes (C10D22 and C14D34) methyl esters (C9H18O2
and C15H30O2) and deuterated PAHs (naphthalene-D8Biphenyl-D8 and Phenanthrene-D10) were used as inter-nal standards (IS) Calibration curves (Concentration (ana-lyte)Concentration (IS) versus Area (analyte)Area (IS))were obtained using at least five concentration levels thatwere replicated 3 times (Table 2) Although the correlationcoefficient of the linear regressions was satisfactory for allcompounds the significance and lack of fit of the modelwere checked by statistical tests before validation A series ofStudent Barlett Chi-square and Fisher tests was run for eachindividual compound using the Lumiere software The bestfitting model was then chosen for each case and confidenceintervals were calculated
4 Results
Altogether 35 hot fluid samples were collected in the studyarea from 8 different sites Kulo Lasi caldera (6) on theone hand and Stephanie (7) Carla (4) IdefX (4) ObelX (3)AsterX (1) Fati Ufu (6) and Tutafi (4) on the other handall located in the Fatu Kapa area (Figure 1) The KuloLasi smokers occurred at sim1500m depth on recent lavaflows and consisted in a multitude of short (sim25 cm) andnarrow (sim3ndash5 cm) diameter anhydrite chimneys containing asmall percentage of sphalerite (ZnS) chalcopyrite (CuFeS2)isocubanite (CuFe2S3) pyrrhotite (Fe1minus119909S) and pyrite (FeS2)(Figure 2)The temperature was consistently about 343∘C andthe pH approached 22ndash23 (Table 3) In the FatuKapa area wecould distinguish two types of hydrothermal environments at1550ndash1650m depth Translucent 270ndash290∘C fluids associatedwith anhydrite chimneys (up to 25m tall and 25m indiameter) characterised Stephanie Carla IdefX ObelX andAsterX sites while gt300∘C milky to grey fluids associatedwith sulphide chimneys were characteristic of the southwestregion including Fati Ufu and Tutafi sites (Figure 3 Table 3)
41 Gas Concentrations of gases in all fluids as well as stableisotopes data are compiled in Table 4 Samples recovered
Geofluids 5
Figure 2 Photographs of sulphide chimneys and young lava flowsobserved on the floor of the Kulo Lasi caldera Copyrights fromIfremer FUTUNA 1 cruise
from Kulo Lasi were extremely poor in CH4 (lt001mM) butcontained the series of C2ndashC5 hydrocarbons Samples fromFatuKapa had higher concentration of CH4 (005ndash0235mM)but only n-pentane (05ndash32 120583M) could be detected andquantified in terms of longer hydrocarbons One samplefrom Kulo Lasi was found to be extremely rich in H2 withnearly 20mM while the others ranged from 1 to 6mM andwere below 005mM at Fatu Kapa H2S was highly variablebetween the 3 sampled chimneys at Kulo Lasi (039 166 and505mM) while it was found rather homogeneous at FatuKapa with values around 1mM CO2 concentrations weremore elevated at Fatu Kapa (45ndash29mM) compared to KuloLasi (1ndash5mM)
Helium isotope ratios were in the range 70ndash99 Ra overthe Fatu Kapa area in agreement with plume data [7] Theycould not be measured at Kulo Lasi unfortunately Carbonisotopes ratios were around minus5permil for CO2 at Fatu Kapawhereas at Kulo Lasi the ratio showed very different results
ranging from minus02 to minus41permil As for methane 12057513C wereslightly lower at Kulo Lasi (simminus28permil) versus Fatu Kapa (simminus23permil) and 120575D was about minus110permil in all samples from FatuKapa 120575D (CH4) could not bemeasured in theKulo Lasi fluidsbecause of the too low concentrations of CH4 Carbon isotoperatios of longer hydrocarbons were in the minus27 to minus22permil atboth vent fields To be noted one sample from Fati Ufu in theFatu Kapa area showed remarkably lower isotopic ratios with12057513C (CO2) = minus23permil 12057513C (CH4) = minus61permil and 120575D (CH4) =minus93permil We do not have any explanation for this but do nothave any reasons either to consider it as an outlier
42 Major and Minor Elements Major and minor elementsmeasurements data are compiled in Table 3 Fluids fromFatu Kapa all exhibited a higher salinity than seawater up to46 wt NaCl whereas at Kulo Lasi fluids with both lower(28 wt NaCl) and higher (43 wt NaCl) salinity weresampled Mg and SO4 concentrations tend to be zero in thepurest samples at Fatu Kapa But the purest fluids from KuloLasi showed significant levels of Mg and SO4 associated withan extremely acidic pH (lt25) and a high119879 (343∘C) Althoughwe cannot totally discard that some mixing with seawateroccurred endmember concentrations of the Kulo Lasi fluidswere then estimated to be close to the purest fluids sampledwhereas they were obtained from mixing lines at Fatu Kapaassuming Mg zero (Table 5)
Fluids from Fatu Kapa were enriched compared to sea-water in alkali alkaline Earth and transition metals as wellas in strontium bromide and silica Conversely the fluidsfrom Kulo Lasi exhibited a much more complex patternThey were all highly enriched in transition metals and silicacompared to seawater and fluids from Fatu Kapa (eg Fe upto sim10mM) The enrichment versus seawater in alkali metalswas not as striking as for Fatu Kapa fluids As for the alkalineEarth metals the amount of Ca was identical to seawater andfluids were depleted in Sr compared to seawater Finally bothdepletion and enrichment in Br were observed in the fluidsfrom Kulo Lasi
43 Organic Geochemistry First of all we would like to men-tion that because solubility of organic compounds decreaseswith119879 and because samples were processed at room tempera-ture the measured concentrations are probably lower than insitu concentrations Moreover it is very likely that a portionof theOMwas adsorbed on small particles in the fluids whichare not taken into account using our extraction and analyticaltechniques As a result the concentrations we report hereprobably represent lower estimates of in situ concentrationsHowever since in situ measurement techniques are notavailable yet these values are the best estimates we can obtainNote that they also are the first to be published for SVOCs
Formate and acetate reached 163 and 155 120583M respec-tively and covaried withMg in the Kulo Lasi fluids (Figure 4)Concentrations of formate and acetate were significantlyhigher in the Fatu Kapa area but no correlation with Mgcould be observed Nevertheless the purest fluids usuallyshowed the highest concentrations Formate reached 68 ppbat Stephanie and 722 ppb at Fati Ufu whereas it could notbe detected at IdefX and Tutafi and was not measured at
6 GeofluidsTa
ble3Measuredconcentrationof
major
andminor
elem
entsin
hydrotherm
alflu
idsfrom
theKu
loLasiandFatu
Kapa
vent
fieldsFU
X-PL
YY-TiD
ZandFU
X-PL
YY-TiGZarereplicate
samplestakenin
thesam
eorifi
ceone
aftertheo
therbut
using2
individu
alTi
syrin
ges119879m
ax(chimney)isthem
axim
um119879o
fthe
discharged
fluidforthe
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neyw
hich
wasrecorded
bythe119879
prob
eofthe
subm
arineb
efores
ampling119879m
ax(sam
ple)isthem
axim
um119879o
fthe
fluid
enterin
gthes
ampler
recorded
durin
gsamplingby
thea
uton
omou
ssensorthatw
ascoup
led
atthen
ozzle
ofthes
ampler
Sample
name
Zone
Site
Descriptio
nDepth119879max
(sam
ple)
∘C
119879max
(chimney)
∘C
pHd20
Kgmminus3
S permilNaC
l(w
t)
Cl mM
Si mM
SO4
mM
Br 120583MNa
mM
K mM
Mg
mM
Ca mM
Li 120583MLi 120583M
Rb 120583MSr 120583M
Fe 120583MMn120583M
Cu 120583MZn 120583M
NaCl
BrC
ltimes103
NaK
CH4M
n
IAPS
O-
-Standard
water
--
--
-35
32
546
00
282
839
468
102
532
103
2727
1390ltLO
DltLO
DltLO
DltLO
D09
1546
-FU
-PL-05-
TiG2
KuloLasi
South(out)
Referencew
ater
1150
--
-10
2335
32
551
01
290
833
457
98532
106
2528
44
93ltLO
DltLO
DltLO
DltLO
D083
1547
-
FU-PL-05-
TiG1
KuloLasi
South(in
)Diffusefl
uidabove
worms
1414
328
-596
1023
3532
549
02
293
833
457
99532
106
2852
46
92ltLO
DltLO
D14
15083
1546
-
FU-PL-06-
TiG4
KuloLasi
North
(in)
Beehivetypeb
lack
smoker
1475
1341
332
607
1022
3330
516
10270
822
448
106
498
105
3354
53
84123
3217
31
087
1642
-
FU-PL-06-
TiD4
KuloLasi
North
(in)
Beehivetypeb
lack
smoker
1475
136
332
558
1021
3128
485
21
239
994
406
95457
102
3255
61
7478
7613
15084
20
430010
FU-PL-06-
TiG3
KuloLasi
North
(in)
Translu
cent
smoker
1475
3423
3307
224
1017
3229
497
82
88
738
388
185
246
116
149
156
2673
4796
862
1445
078
1521
0007
FU-PL-06-
TiD3
KuloLasi
North
(in)
Translu
cent
smoker
1475
3377
3307
237
1018
3330
517
84
107
770
405
166
286
108
115149
2494
4283
788
42
41078
1524
-
FU-PL-06-
TiD1
KuloLasi
North
(in)
Blacksm
oker
1475
3432
3451
236
102
4743
735
146
62
1135
612
295
265
109
238
249
4634
9884
1416
25
175
083
1521
-
FU-PL-06-
TiG1
KuloLasi
North
(in)
Blacksm
oker
1475
3432
3451
332
1028
4440
689
108
120
1051
565
237
349
108
176
197
3691
6845
1064
2077
082
1524
0001
FU3-PL
-03-
TiD3
Fatu
Kapa
20masf
Referencew
ater
1488
--
--
-33
565
00
288
841
483
104
545
107
2251
6ltLO
DltLO
DltLO
DltLO
DltLO
D085
1546
-
FU3-PL
-14-
TiG2
Fatu
Kapa
23masf
Referencew
ater
1572
2-
--
3633
557
00
287
841
477
104
542
108
23nm
nmnm
nmnm
nmnm
086
1546
-
FU3-PL
-04-
TiD3
Fatu
Kapa
Stephanie
Translu
cent
smoker
1554
213
279
465
103
4541
704
07
109
1300
519
398
187
696
472
568
80ltLO
D169
166
nmltLO
D074
1813
-
FU3-PL
-04-
TiG3
Fatu
Kapa
Stephanie
Translu
cent
smoker
1554
213
279
464
103
4440
686
10129
1240
513
365
225
628
420
504
71169
nm141
82ltLO
D075
1814
0805
FU3-PL
-08-
TiD1
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
289
280
410
3149
45
770
38
131574
535
542
08
989
705
804
121
268
655
265
66ltLO
D069
20
100886
FU3-PL
-08-
TiG1
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
289
280
341
1031
4945
772
47
07
1592
537
547
05
987
708
807
122
283
167
269
nmltLO
D070
21
100762
FU3-PL
-08-
TiD2
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
291
280
383
1031
4844
748
43
05
1537
520
529
06
953
684
806
116ltLO
D148
259
nmltLO
D070
21
10-
FU3-PL
-09-
TiD2
Fatu
Kapa
Stephanie
Beehivetypeb
lack
smoker
+bacterial
mat
1650
197
236
519
1026
4037
629
17198
1052
500
244
374
378
230
293
36149
nm65
nm10
079
1721
0902
FU3-PL
-09-
TiG2
Fatu
Kapa
Stephanie
Beehivetypeb
lack
smoker
+bacterial
mat
1559
197
236
542
1025
3835
600
10238
959
489
185
443
264
143
193
23ltLO
Dnm
23nmltLO
D081
1626
-
FU3-PL
-06-
TiD1
Fatu
Kapa
Carla
Translu
cent
smoker
1663
278
270
503
1024
3734
576
17185
927
482
285
352
179
260
310
42101
nmnm
nmltLO
D084
1617
-
FU3-PL
-06-
TiG1
Fatu
Kapa
Carla
Translu
cent
smoker
1663
278
270
491
1024
3734
579
07
127
984
476
378
236
222
391
455
63ltLO
D18
32nmltLO
D082
1713
-
FU3-PL
-08-
TiD3
Fatu
Kapa
Carla
Translu
cent
smoker
1664
281
281
278
1024
3835
594
45
11113
9479
596
04
315
690
746
104
115nm
48nm
44
080
198
1365
FU3-PL
-08-
TiG3
Fatu
Kapa
Carla
Translu
cent
smoker
1664
281
281
417
1024
3835
592
40
19112
0477
577
27
303
655
720
96ltLO
D288
39nmltLO
D081
198
-
FU3-PL
-11-
TiD3
Fatu
Kapa
IdefX
Translu
cent
smoker
1573
259
258
49
1025
4137
637
1483
1142
509
498
155
350
541
612
78ltLO
D38
26nmltLO
D080
1810
-
FU3-PL
-11-
TiG3
Fatu
Kapa
IdefX
Translu
cent
smoker
1573
259
258
443
1025
4339
664
41
191268
518
635
20
447
733
802
110160
nm46
nm25
078
198
1848
Geofluids 7
Table3Con
tinued
Sample
name
Zone
Site
Descriptio
nDepth119879max
(sam
ple)
∘C
119879max
(chimney)
∘C
pHd20
Kgmminus3
S permilNaC
l(w
t)
Cl mM
Si mM
SO4
mM
Br 120583MNa
mM
K mM
Mg
mM
Ca mM
Li 120583MLi 120583M
Rb 120583MSr 120583M
Fe 120583MMn120583M
Cu 120583MZn 120583M
NaCl
BrC
ltimes103
NaK
CH4M
n
FU3-PL
-14-
TiD1
Fatu
Kapa
IdefX
Translu
cent
smoker
1572
271
271
373
1025
4339
665
42
111282
519
662
08
434
764
823
120
144
2864
nm34
078
198
1078
FU3-PL
-14-
TiG1
Fatu
Kapa
IdefX
Translu
cent
smoker
1572
271
271
397
1025
4239
661
41
08
1279
515
657
08
429
757
825
119ltLO
Dnm
62nmltLO
D078
198
-
FU3-PL
-14-
TiD2
Fatu
Kapa
ObelX
Translu
cent
smoker
1669
272
-459
103
4945
769
45
07
1506
577
694
13655
757
nmnm
nmnm
nmnm
nm075
20
8-
FU3-PL
-14-
TiD3
Fatu
Kapa
ObelX
Translu
cent
smoker
1636
287
-428
103
4743
729
37
150
1283
557
588
111
650
621
nmnm
nmnm
nmnm
nm076
189
-
FU3-PL
-14-
TiG3
Fatu
Kapa
ObelX
Translu
cent
smoker
1636
287
-537
1028
4339
672
25
270
1103
528
425
253
546
415
nmnm
nmnm
nmnm
nm079
1612
-
FU3-PL
-18-
TiD1
Fatu
Kapa
AsterX
Translu
cent
smoker
1540
265
260
435
1027
4441
693
37
101344
533
649
12511
755
nmnm
nmnm
nmnm
nm077
198
-
FU3-PL
-17-
TiD2
Fatu
Kapa
FatiUfu
Greysm
oker
1522
299
303
426
1031
4743
739
33
931378
555
384
176
666
543
nmnm
nmnm
nmnm
nm075
1914
-
FU3-PL
-17-
TiG2
Fatu
Kapa
FatiUfu
Greysm
oker
1522
299
303
422
1031
4844
748
35
87
1402
562
398
159
697
569
nmnm
nmnm
nmnm
nm075
1914
-
FU3-PL
-21-
TiD1
Fatu
Kapa
FatiUfu
Greysm
oker
1523
302
301
381
1032
5046
784
47
141554
577
473
14862
717
nmnm
nmnm
nmnm
nm074
20
12-
FU3-PL
-21-
TiG1
Fatu
Kapa
FatiUfu
Greysm
oker
1523
302
301
469
103
4541
708
27
105
1292
544
347
193
603
474
nmnm
nmnm
nmnm
nm077
1816
-
FU3-PL
-21-
TiD2
Fatu
Kapa
FatiUfu
Whitesm
oker
1503
-284
327
1028
4441
694
49
04
1359
534
393
10633
573
nmnm
nmnm
nmnm
nm077
20
14-
FU3-PL
-21-
TiG2
Fatu
Kapa
FatiUfu
Whitesm
oker
1503
-284
422
1026
4239
661
39
701217
520
320
133
506
435
nmnm
nmnm
nmnm
nm079
1816
-
FU3-PL
-20-
TiD1
Fatu
Kapa
Tutafi
Greysm
oker
1580
316
317
41
1029
4642
720
26
06
1409
543
546
09
654
628
nmnm
nmnm
nmnm
nm075
20
10-
FU3-PL
-20-
TiG1
Fatu
Kapa
Tutafi
Greysm
oker
1580
316
317
414
1029
4642
723
23
101409
543
547
07
664
630
nmnm
nmnm
nmnm
nm075
1910
-
FU3-PL
-21-
TiD3
Fatu
Kapa
Tutafi
Whitesm
oker
1626
293
294
292
1028
4541
701
51
09
1367
528
513
03
639
640
nmnm
nmnm
nmnm
nm075
1910
-
FU3-PL
-21-
TiG3
Fatu
Kapa
Tutafi
Whitesm
oker
1626
293
294
365
1027
4541
700
50
08
1371
528
510
08
633
633
nmnm
nmnm
nmnm
nm075
20
10-
8 Geofluids
Table4
Measuredgascon
centratio
nandassociated
stableiso
topicratiosh
ydrothermalflu
idsfromtheK
uloL
asiand
FatuKa
paventfieldsVa
luesoflogfH2werec
alculated
usingS
UPC
RT92
with
thes
lop9
8database
Samplen
ame
Site
H2S
N2
3He
RRa
H2
logfH2
CH4
CO2
C 2H6
C 2H4
C 3H8
C 3H6
n-C 4
H10n-C 5
H12120575D(H2)120575D(C
H4)12057513C(C
O2)12057513C(C
H4)12057513C(C2H6)12057513C(C3H8)12057513C(C4H10)
mM
mM
mM
mM
mM
mM120583M120583M120583M120583M120583M
120583M
permilpermil
permilpermil
permilpermil
permilSeaw
ater
059
nmnmltLO
D-ltLO
D23
nmnm
nmnm
nmnm
nmnm
nmnm
nmnm
nmFU
-PL-05-TiG1
KuloLasi
012
nmnmltLO
Q-
0001
26ltLO
DnmltLO
DnmltLO
DltLO
Dnm
nmnm
nmnm
nmnm
FU-PL-06-TiD
4Ku
loLasi
166
010
nmnm
114
-0001
13002
0005
000
6000
40005
0005minus323
nm
minus32
minus29
minus27
minus26
nmFU
-PL-06-TiG3
KuloLasi
505
143
nmnm
198minus311
000
651
011
004
20028
0030
0024
000
6minus306
nm
minus41
minus23
minus26
minus26
minus24
FU-PL-06-TiD
1Ku
loLasi
039
248
nmnm
618minus362
000
430
01
0017
0017
0020
0012
000
4minus300
nm
minus19
minus28
minus24
minus26
minus24
FU-PL-06-TiG1
KuloLasi
079
nmnm
104minus440
0001
10002
000
90005
0007
0005
0001minus316
nm
minus02
minus272
minus22
minus26
minus24
FU3-PL
-04-TiG3
Stephanie
091
09311119864minus08
86
003minus18
70114
155ltLO
DltLO
DltLO
DltLO
DltLO
D17
nmnm
nmnm
nmnm
nmFU
3-PL
-08-TiD1
Stephanie
123
198
nm006minus15
70235
290ltLO
DltLO
DltLO
DltLO
DltLO
D32minus676minus108
minus5
minus217
nmnm
nmFU
3-PL
-08-TiG1
Stephanie
098
24744119864minus09
76005minus16
50205
257ltLO
DltLO
DltLO
DltLO
DltLO
D29
nmnm
nmnm
nmnm
nmFU
3-PL
-09-TiD2
Stephanie
023
04819119864minus09
70004minus17
50059
60ltLO
DltLO
DltLO
DltLO
DltLO
D07minus436minus111
minus53
minus222
nmnm
nmFU
3-PL
-06-TiD1
Carla
134
05071119864minus09
96001minus235
0021
45ltLO
DltLO
DltLO
DltLO
DltLO
D05
nmnm
nmnm
nmnm
nmFU
3-PL
-08-TiD3
Carla
019
33317119864minus08
98005minus16
5006
6119ltLO
DltLO
DltLO
DltLO
DltLO
D15
minus410minus109
minus47
minus215
nmnm
nmFU
3-PL
-11-T
iG3
Idef
X113
07818119864minus08
98003minus18
70085
100ltLO
DltLO
DltLO
DltLO
DltLO
D11
nmnm
nmnm
nmnm
nmFU
3-PL
-14-TiD1
Idef
X10
012
055119864minus09
87
002minus205
0069
101ltLO
DltLO
DltLO
DltLO
DltLO
D11
minus417minus110
minus49
minus238
nmnm
nmFU
3-PL
-14-TiD2
ObelX
085
10538119864minus08
98003minus18
70110
87ltLO
DltLO
DltLO
DltLO
DltLO
D10
minus40
7minus113
minus5
minus24
nmnm
nmFU
3-PL
-14-TiD3
ObelX
054
09352119864minus09
84
002minus205
0165
92ltLO
DltLO
DltLO
DltLO
DltLO
D10
nmnm
nmnm
nmnm
nmFU
3-PL
-18-TiD1
AsterX
098
089
nmnm
001minus235
0067
92ltLO
DltLO
DltLO
DltLO
DltLO
D10
minus412minus111
minus49
minus236
nmnm
nmFU
3-PL
-17-TiG2
FatiUfu
176
08427119864minus08
99001minus259
0070
215ltLO
DltLO
DltLO
DltLO
DltLO
D23
-minus93
minus23
minus61
nmnm
nmFU
3-PL
-21-T
iD2
FatiUfu
071
20731119864minus09
99003minus211
0111
126ltLO
DltLO
DltLO
DltLO
DltLO
D15
minus410minus109
minus44
minus233
nmnm
nmFU
3-PL
-20-TiD1
Tutafi
236
11814119864minus08
92005minus18
90156
222ltLO
DltLO
DltLO
DltLO
DltLO
D24minus396minus111
minus45
minus236
nmnm
nmFU
3-PL
-21-T
iD3
Tutafi
084
167
nmnm
003minus211
0053
117ltLO
DltLO
DltLO
DltLO
DltLO
D14
minus415minus109
minus47
minus242
nmnm
nm
Geofluids 9
Table5En
dmem
bercom
positions
influ
idsfrom
theK
uloLasiandFatu
Kapa
vent
fieldsKu
loLasiendm
emberscann
otbe
extrapolated
atMg=
0Va
luespresentedhereforb
othbrinea
ndcond
ensedvapo
urph
ases
correspo
ndto
concentrations
inthefl
uidwith
thelow
estM
gElem
entalcom
positions
inendm
emberfl
uids
from
thev
arious
sites
oftheF
atuKa
pavent
field
were
calculated
usingthem
ixinglin
es(FigureS
1)andassumingMg=0Va
lues
ofthep
urestfl
uidwereu
sedwhenlin
earregressionwas
notp
ossib
le(lowast)Notethato
nlyon
esam
plew
asavailable
forthe
AsterX
site(1)
Zone
Site
Depth119879
pHNaC
lCl
SiSO
4Br
Na
KMg
CaLi
RbSr
FeMn
CuZn
NaCl
BrC
lNaK
CH4Mn
∘ C(w
t)
mM
mM
mM120583M
mM
mM
mM
mM120583M120583M120583M
120583M120583M
120583M120583M
times103
KuloLasi
NaC
lpoo
r1475
345
224
29
497
82
88
738
388
185
246
116
149
2673
4796
862
1445
078
148
210007lowast
KuloLasi
NaC
lrich
1475
345
236
43
735
146
62
1135
612
295
265
109
238
4634
9884
1416
25
175
083
154
210001lowast
Fatu
Kapa
Stephanie
1555
280
34
45
767
47lowast
00
1569
532
545
00
989
708
114282lowast
655lowast
268
66lowastltL
OD
069
205
10076lowast
Fatu
Kapa
Carla
1664
280
28
35
594
43
00
1132
477
599
00
314
691
105
114lowast
287lowast
53nm
44lowast
080
190
813
7lowast
Fatu
Kapa
Idef
X1572
270
37
39
665
42lowast
00
1282
518
664
00
443
751
113
160lowast
28lowast
60nm
34lowast
078
193
810
8lowast
Fatu
Kapa
ObelX
1669
270
46
45
771
46
00
1458
580
710
00
859
777
nmnm
nmnm
nmnm
075
189
8-
Fatu
Kapa
AsterX(1)
1540
265
44
41
693
37
101344
533
649
12511
755
nmnm
nmnm
nmnm
077
194
8-
Fatu
Kapa
FatiUfu
1523
300
38
46
790
49
00
1589
580
482
00
854
722
nmnm
nmnm
nmnm
073
201
12-
Fatu
Kapa
FatiUfu
1503
280
33
41
700
49
00
1380
538
400
00
650
583
nmnm
nmnm
nmnm
077
197
13-
Fatu
Kapa
Tutafi
1580
315
41
42
713
51
00
1405
535
529
00
651
635
nmnm
nmnm
nmnm
075
197
10-
IAPS
OStandard
sw-
--
32
546
00
282
839
468
102
532
103
2713
90ltLO
DltLO
DltLO
DltLO
D09
1546
-Ku
loLasi
References
w1150
--
32
551
01
290
833
457
98532
106
2544
93ltLO
DltLO
DltLO
DltL
OD
083
1547
-Fatu
Kapa
References
w1488
--
33
565
00
288
841
483
104
545
107
2258ltLO
DltLO
DltLO
DltLO
DltL
OD
085
1546
-Fatu
Kapa
References
w1572
2-
33
557
00
287
841
477
104
542
108
23nm
nmnm
nmnm
nm086
1546
-lowastMaxim
umvaluew
henlin
earregressionwas
notp
ossib
le(1)on
lyon
esam
ple
10 Geofluids
(a)
(b)
(c)
Figure 3 (a) and (b) Photographs of anhydrite structures observed at Stephanie Carla IdefX AsterX and ObelX site (c) Photographs of greysmokers associated with sulphides structures observed at Fati Ufu and Tutafi Copyrights from Ifremer FUTUNA 3 cruise
02468
1012141618
0 10 20 30 40 50 60Mg (mM)
Kulo Lasi
AcetateFormate
SW-acetateSW-formate
Con
cent
ratio
n(
M)
Figure 4 Mixing lines of formate and acetate versus Mg for the Kulo Lasi fluids Note that the reference deep-sea water sample (FU-PL05-TiG2 noted as SW here) was taken at 1150m depth above the southern wall of the caldera (see Figure 1 for location and Table 3) and thus verylikely within the plume [7] This would account for the unusual concentrations of formate and acetate detected
Geofluids 11
Carla Acetate was detected in all analysed samples andconcentrations were an order of magnitude higher than theones of formate (543ndash2309 ppb) (Table 6)
Heavier extractable organic compounds were notdetected in the dry control experiment and only a few weredetectable but below limit of quantification (LOQ) in theMQ water blank experiment (Table 6) This showed thatsample preparation and storage could be considered ascontamination-free steps The levels of heavier extractableorganic compounds appeared rather high in the referencewater at Fatu Kapa certainly because of the overall spreadhydrothermal discharges and diffuse venting in the region [7](Table 6 Figure 5) This sample was indeed taken mid-waybetween ObelX and AsterX fields at about 20m above theseafloor As a consequence it is difficult to assess possiblecontamination originating from sampling device or seawatercontribution in the present case However earlier studieshave shown that they generally did not represent majorsources of contamination as for the studied compounds[27 37] Nevertheless in comparison to deep-sea waterboth the qualitative (Kulo Lasi) and quantitative (FatuKapa) data obtained suggested enrichment of the fluidsin hydrothermally derived compounds namely n-alkanes(C9ndashC12) n-FAs (C9 C12 C14ndashC18) and PAHs (fluorenephenanthrene pyrene) ([39] Table 6 Figures 5 and 6)Such enrichment was unclear for gtC12 n-alkanes C10C11 C13 n-FAs BTEXs naphthalene acenaphthene andfluoranthene because of their very low concentration andorthe measurement uncertainty
Differences in concentrations seemed to exist among thevents over the Fatu Kapa area Fluids from the Stephanie ventfield had concentrations in hydrocarbons equal or below thereference water sample whereas they were clearly enrichedin C9 C12 C14ndashC18 n-FAs The Carla fluids were slightlyenriched in C9ndashC12 n-alkanes and showed the highest con-centrations in PAHs Fluids from IdefX Fati Ufu and Tutafishared some similarities a strong enrichment in decane andundecane alike concentrations in PAHs and the presence ofsignificant amounts of xylene However fluids expelled at theTutafi vent appeared the most enriched in C9ndashC11 n-alkanesand xylenes In terms of fatty acids and considering theanalytical error the 5 vents showed consistent concentrationswith C9 C16 and C18 being major Note that fluids from FatiUfu seemed depleted in C17 and C18
Generally we did not observe strong linear correlationbetween the concentration of individual compounds andMgNonetheless these relations showed that both enrichmentand depletion of organic compounds seemed to occur inhydrothermal fluids versus deep-sea water
5 Discussion
The elemental and gas composition of hydrothermal fluidsis mainly affected by waterrock interactions and thus thenature of the host rocks phase separation magmatic fluidcontribution conductive cooling and seawater mixing inlocal recharge zones [45] In the following discussion weattempt to unravel the occurrence of these various processes
both at Kulo Lasi and at Fatu Kapa Much less is known onprocesses that control organic geochemistry and are thereforediscussed here as well as some implications of the presenceof organic compounds in hydrothermal fluids Implicationsrelated to the composition of the fluids are dependent onfluxes therefore we give here an attempt to provide order ofmagnitude estimates of heat and mass fluxes
51 Plume-Fluids Relations The geochemistry and dynamicsof the plumes over the Wallis and Futuna region havebeen studied elsewhere [7] The Kulo Lasi plume has beenproposed to be the result of both high-119879 and diffuse ventingfrom multiple vents located both on the floor and on thewall of the caldera Consistently both types of venting havebeen observed [6] Helium nephelometry and Mn profilesrecorded above the northern sampling area showed constantelevated concentrations in the 300masf and were assumedto be the results of diffuse venting Our results show thatthey are obviously the result of the numerous small blacksmokers observed on the seafloor (Figure 2) The methaneconcentration in the sampled fluids was extremely low whichcannot account for the elevated concentration of CH4 inthe water column reported by Konn et al [7] The strongdifference in the CH4Mn ratios between the plume (07ndash45)and the sampled fluids (0001ndash001) is another line of evidencethat the methane plume has another origin compared tohydrothermal fluids and likely come from degassing of thelava flows as suggested by the authors Although other fluiddischarges likely remain undiscovered this is consistent witha past eruption and accumulation of the water mass in thecaldera [39]
A great diversity of the fluid compositions was expectedfrom the geological settings and the water column survey andwas indeed confirmed by the mixing lines that point to asmany endmembers as sampled areas (Figure S1) CH4TDMratios also differed among the vents but it was not due to soleCH4 concentration variations as suggested earlier (Table 5)[7] Finally the very weak nephelometry of the Fatu Kapaplume is likely best explained by the low metal contents ofthe fluids
52 Reaction Zone Depth The solubility of Quartz in hydro-thermal fluids has been studied by different authors (eg[46]) According to these works silica concentration in thefluid may be used to estimate the depth of the reaction zoneThe silica concentration measured in the Kulo Lasi and FatuKapa fluids indicates a hydrothermal reaction zone at seaflooror in thewater column (Figure S2) Both observations suggestthat in this area fluids are not in equilibria with Quartz atthe pressure and temperature of the fluid emission And thisprevents using Si as a geothermometer to determine the depthof the reaction zone
All fluids at Fatu Kapa were indeed highly depleted inSi with respect to the Quartz saturation curve at 170 bar300∘C (Si sim12mM in Figure S2) A higher temperature inthe reaction zone (gt350∘C at 200 bar) may explain a lower Siconcentration in the fluid at equilibrium as Quartz solubilitydecreases (Figure S2) The dispersion of a great number of
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Organic geochemistry of hydrothermal fluids has gen-erally been far less studied than the mineral and gas geo-chemistry In most cases works focused on small molecules(hydrocarbon gases volatile fatty acids and amino acids)and very few data are available on semivolatile organiccompounds (SVOCs) Despite the growing interest for OM inthe ocean and hydrothermal systems there is still a major lackin identification and quantification of organic compounds[10ndash15] Notably numbers of studies agree on the majorligand role of organics in metal stabilisation transportationbioavailability and ore-forming but there are hardly any clueson the nature of these ligands in hydrothermal environments[16ndash25] Organic compounds in hydrothermal fluids maycome frommarine dissolved organicmatter (DOM) recycling[12 13] subsurface biomass degradation [26] entrainment oforganic detritus from local recharge zones and subsequentdegradation or abiotic formation in the deep subsurface[27ndash30] The latter is supported by many theoretical [31ndash33] and experimental work summarised in two reviews [3435] Conversely some other studies reported the absence oforganic compounds in hydrothermal fluids except at the LostCity alkaline vent field which is theoretically more favourablefor abiotic synthesis [36] Nevertheless we report here thepresence of semivolatile organic compounds in hydrother-mal fluids from the Wallis and Futuna area and provideconcentrations of a selection of extractable compounds thathave been identified elsewhere as hydrothermally derived[27 37] n-alkanes n-fatty acids (n-FAs) mono- and pol-yaromatic hydrocarbons (BTEXs and PAHs) These very firstquantitative field data might feed thermodynamic models ofabiotic synthesis guide the design of experiments to betterunderstand hydrothermal organic geochemistry and helpassessing the importance of hydrothermally derived organiccompounds in metal complexation and as a nutrient formicroorganisms complete fluxes calculation and enter in thecarbon cycle budget calculations
2 Geological Settings
Wallis and Futuna Islands are located at the transitionbetween the North Fiji and the Lau back-arc basins Thisgeodynamical setting accounts for complex volcanic andtectonic activity in the area Pelletier et al [38] and Fouquetet al [6] observedmultiple active extensional zones includingwidespread areas composed of numerous individual volca-noes (eg Southeast Futuna volcanic zone (SEVZ)) and wellorganised spreading centers such as the Futuna and Alofioceanic ridge West of Futuna Island the 20ndash30∘ trendingFutuna spreading center (FSC) is composed of a series of enechelon spreading segmentsThe opening rate of this oceanicridge has been estimated at 4 cmyr from the interpretationof magnetic anomalies [38] East and southeast of FutunaIsland bathymetric maps and reflectivity data clearly revealthat active extension and recent volcanism occur in the SEVZas well as along the Alofi spreading center [6] The SEVZ is abroad zone of diffuse volcanism bordered by the ENE-WSWtrending volcanic graben (named Tasi Tulo graben) to thenorth and the NNE-SSW trending Alofi spreading center to
the south The SEVZ includes Kulo Lasi active volcano theFatu Kapa and Tasi Tulo volcanic zones ([7] Figure 1)
Fluids were sampled at the Kulo Lasi and Fatu Kapa sitesKulo Lasi has been described in detail by Fouquet and collab-orators [39] In summary it is a shield volcano located about100 km southeast of Futuna Island (Figure 1) It representsthe most recent volcano in the SEVZ and is composed ofbasaltic to trachy-andesitic lava with no direct geochemicalaffinity with subduction [39]The volcanic edifice is ca 20 kmin diameter and appears relatively flat with the top located ata depth of 1200m and the base only 300m deeper (ca 1500mbelow sea level) It exhibits a central caldera (5 km in diameterand 200ndash300m deep) with a flat bottom covered by recentlavas and a central mound composed of older and tectonisedlava flow By contrast the Fatu Kapa volcanic area is in a20 km wide transition zone between the Tasi Tulo grabenand the Kulo Lasi volcano Here only small (lt1 km) volcanicedifices are seen to be consisting of youngmafic to felsic lavas(Figure 1)
3 Sampling and Analytical Procedures
Sampling was achieved at Kulo Lasi and Fatu Kapa bythe HOV Nautile during the FUTUNA 1 and FUTUNA3 cruises conducted by Ifremer in 2010 and 2012 Fluidsamples were taken at the nose of smokers to minimiseseawater contamination Samples of volumes up to 750mL ofhydrothermal fluids were collected in titanium syringes thatwere modified after the model described in Von Damm et al[40]The gas-tightness was greatly improved and ensured themajority of the gas to be recoveredThose same syringes havebeen used in several studies by Charlou et al and have showngood results notably for gas-Mg correlations (eg Charlouet al 2002) Autonomous temperature sensors (S2T 6000-DH NKE Instrumentation) were mounted on the samplernozzle As soon as the fluids were recovered pH H2S andClminus concentrations were measured to evaluate the qualityof the sample Total gases were immediately extracted andanalysed then aliquots of gas were conditioned for furtherstable isotopes measurements Finally the gas-free fluid wasconditioned for major and minor elements analyses on theone hand and for organic compounds analyses on the otherhand
31 Gas Extraction and Analyses Total gas was extracted asdescribed in Charlou and Donval [41] Preliminary majorgases (CO2 H2 CH4 and N2) concentrations were obtainedon board by using a portable chromatograph (MicrosensorTechnology Instruments Inc) that was mounted on linewith the gas extractor Extracted gases were conditionedon board in stainless steel pressure-tight flasks and storeduntil analyses Gases were separated byGas-Chromatography(Agilent GC 7890A Agilent Technologies) and quantitativelyanalysed by triple detection using mass (MS 5975C Agilenttechnologies) flame ionisation and thermal conductivitydetectors Aliquots of gas were stored both in vacuum tighttubes (Labco Ltd) and in copper tubes to be sent for furthercarbon isotope analyses (Isolab bv Netherlands) and Heisotopes analyses (CEA Saclay France) respectively
Geofluids 3
Figure 1 Bathymetric map of the study area Close-ups of Fatu Kapa and Kulo Lasi are shown in boxes where sample positions are markedwith red disks Copyrights from Ifremer FUTUNA 1 2 and 3 cruises
32 Inorganic Geochemistry Sample Preparation and Anal-yses pH was measured using a combined glass electrode(Ecotrode Plus Metrohm) Clminus and H2S were measured bypotentiometry using AgNO3 (005M) and HgCl2 (001M) astitrating solutions respectivelyNaOH (2M)was added to thealiquot before H2S measurement SO4 Br Na K Mg Ca Liand Cl were measured by ionic chromatography (Dionex IonChromatograph System 2000) after appropriate dilutions FeMn Cu Zn Sr Li and Rb were measured by flame atomicabsorption spectrometry using standard additions (AAnalystPerkin Elmer Inc) Aliquots for silica determination wereimmediately diluted 100- to 200-fold and analysed by thesilicomolybdate automatic colorimetric method [42 43]
33 Organic Geochemistry Total Organic Carbon (TOC)was measured using a multi NC 3100 (Analytik Jena AGGermany) Samples were acidified online with HCl and thenpurged with O2 to remove inorganic carbon (IC) A TIC
control analysis was performed and followed by three TOCmeasurements on each sample
Acetate and formate concentrations were determinedusing a Dionex ICS-2000 Reagent-Free Ion Chromatogra-phy System equipped with an AS50 autosampler (DionexCamberley UK) Chromatographic separationwas conductedusing two Ionpac AS15 columns in series at 30∘C and thedetermination of species was carried out using an AnionSelf-Regenerating Suppressor (ASRS 300 4mm) unit in com-bination with a DS6 heated conductivity cell (35∘C) Thegradient program was as follows 6mmol Lminus1 KOH (43min)increase from 27mmol Lminus1 KOH minminus1 to 60mmol Lminus1(39min) decrease from 54mmol Lminus1 KOHminminus1 to 6mmolLminus1 (5min)
SVOCs were extracted using Stir Bar Sorptive Extraction(SBSE) Basically any compound with a log Kow gt 25 isrecovered with a rate gt 50 [44] The method was improvedafter Konn et al [37] The entire content of the titanium
4 Geofluids
Table 1 Main GC analytical parameters used for calibration and analyses of hydrothermal fluid samples Each group of compounds (n-alkanes BTEXs PAHs and n-fatty acids) was analysed using separate twisters
n-Alkanes BTEX amp PAHs n-Fatty acidsOvenInitial 119879 (∘C) 40 40 40Initial 119905 (min) 1 1 1ramp 40 to 320∘C at 12∘Cmin 40 to 320∘C at 12∘Cmin 40 to 320∘C at 20∘CminFinal 119879 (∘C) 320 320 320Final 119905 (min) 2 2 2Injector119879 (∘C) 250 250 325
Table 2 Experimental conditions used for calibration curves Linear regressions were performed on one order of magnitude concentrationdomain depending on the concentration range of the samples
syringe was transferred into a precombusted glass bottle andsix 90mL aliquots of the sample were poured into 100mLprecombusted glass vials 10mL ofMeOHwas added to avoidadsorption of the compounds onto the wall of the vialsInternal standards were added to the solutions in 2012 so thatquantification could only be achieved in Fatu Kapa fluidsExtraction was performed in sealed vials with ultrainertseptum crimps at 300 rpm and using 48 120583L PDMS Twisters(Gerstel GmbH) We focused on a selection of chemicalgroups that had previously been described as hydrothermallyderived [27] To that respect pairs of aliquots were dedicatedto analysis of n-alkanes n-FAs and both BTEXs and PAHsrespectively Extraction kinetics experiments showed thatchemical equilibrium was reached after 5 h of extraction forn-alkanes 4 h for PAHs and 14 h for n-FAs (Konn unpub-lished results) Twisters were then removed rinsed with MQwater dried and stored at +4∘C until analyses by ThermalDesorption-Gas Chromatography-Mass Spectrometry (TD-GC-MS) [37] Analytical parameters were adjusted for eachgroup of compounds (Table 1)
For each batch of conditioned Twisters one was sparedstored at +4∘C and analysed in the same run as the otherTwistersThis dry blank aimed at showing any contaminationthat could have occurred during conditioning storage andtransport MQ water samples were prepared and extractedon board as regular hydrothermal samples to check if anycontaminations could have occurred during the samplepreparation step Deep-sea water was also collected pro-cessed and analysed using the same titanium syringes andaccording to the same protocols as for hydrothermal fluidsamples and thus constitute the reference blank experiment
Calibration was achieved using a commercial stan-dard solution of BTEXs and 3 custom standard solu-tions of C9ndashC20 n-alkanes C6ndashC18 n-FAs and PAHs con-taining naphthalene (N) Acenaphtene (A) Fluorene (F)Phenanthrene (Ph) Anthracene (An) Fluoranthene (Fl)and pyrene (Py) (LGC Standards LGC Ltd) Deuteratedn-alkanes (C10D22 and C14D34) methyl esters (C9H18O2
and C15H30O2) and deuterated PAHs (naphthalene-D8Biphenyl-D8 and Phenanthrene-D10) were used as inter-nal standards (IS) Calibration curves (Concentration (ana-lyte)Concentration (IS) versus Area (analyte)Area (IS))were obtained using at least five concentration levels thatwere replicated 3 times (Table 2) Although the correlationcoefficient of the linear regressions was satisfactory for allcompounds the significance and lack of fit of the modelwere checked by statistical tests before validation A series ofStudent Barlett Chi-square and Fisher tests was run for eachindividual compound using the Lumiere software The bestfitting model was then chosen for each case and confidenceintervals were calculated
4 Results
Altogether 35 hot fluid samples were collected in the studyarea from 8 different sites Kulo Lasi caldera (6) on theone hand and Stephanie (7) Carla (4) IdefX (4) ObelX (3)AsterX (1) Fati Ufu (6) and Tutafi (4) on the other handall located in the Fatu Kapa area (Figure 1) The KuloLasi smokers occurred at sim1500m depth on recent lavaflows and consisted in a multitude of short (sim25 cm) andnarrow (sim3ndash5 cm) diameter anhydrite chimneys containing asmall percentage of sphalerite (ZnS) chalcopyrite (CuFeS2)isocubanite (CuFe2S3) pyrrhotite (Fe1minus119909S) and pyrite (FeS2)(Figure 2)The temperature was consistently about 343∘C andthe pH approached 22ndash23 (Table 3) In the FatuKapa area wecould distinguish two types of hydrothermal environments at1550ndash1650m depth Translucent 270ndash290∘C fluids associatedwith anhydrite chimneys (up to 25m tall and 25m indiameter) characterised Stephanie Carla IdefX ObelX andAsterX sites while gt300∘C milky to grey fluids associatedwith sulphide chimneys were characteristic of the southwestregion including Fati Ufu and Tutafi sites (Figure 3 Table 3)
41 Gas Concentrations of gases in all fluids as well as stableisotopes data are compiled in Table 4 Samples recovered
Geofluids 5
Figure 2 Photographs of sulphide chimneys and young lava flowsobserved on the floor of the Kulo Lasi caldera Copyrights fromIfremer FUTUNA 1 cruise
from Kulo Lasi were extremely poor in CH4 (lt001mM) butcontained the series of C2ndashC5 hydrocarbons Samples fromFatuKapa had higher concentration of CH4 (005ndash0235mM)but only n-pentane (05ndash32 120583M) could be detected andquantified in terms of longer hydrocarbons One samplefrom Kulo Lasi was found to be extremely rich in H2 withnearly 20mM while the others ranged from 1 to 6mM andwere below 005mM at Fatu Kapa H2S was highly variablebetween the 3 sampled chimneys at Kulo Lasi (039 166 and505mM) while it was found rather homogeneous at FatuKapa with values around 1mM CO2 concentrations weremore elevated at Fatu Kapa (45ndash29mM) compared to KuloLasi (1ndash5mM)
Helium isotope ratios were in the range 70ndash99 Ra overthe Fatu Kapa area in agreement with plume data [7] Theycould not be measured at Kulo Lasi unfortunately Carbonisotopes ratios were around minus5permil for CO2 at Fatu Kapawhereas at Kulo Lasi the ratio showed very different results
ranging from minus02 to minus41permil As for methane 12057513C wereslightly lower at Kulo Lasi (simminus28permil) versus Fatu Kapa (simminus23permil) and 120575D was about minus110permil in all samples from FatuKapa 120575D (CH4) could not bemeasured in theKulo Lasi fluidsbecause of the too low concentrations of CH4 Carbon isotoperatios of longer hydrocarbons were in the minus27 to minus22permil atboth vent fields To be noted one sample from Fati Ufu in theFatu Kapa area showed remarkably lower isotopic ratios with12057513C (CO2) = minus23permil 12057513C (CH4) = minus61permil and 120575D (CH4) =minus93permil We do not have any explanation for this but do nothave any reasons either to consider it as an outlier
42 Major and Minor Elements Major and minor elementsmeasurements data are compiled in Table 3 Fluids fromFatu Kapa all exhibited a higher salinity than seawater up to46 wt NaCl whereas at Kulo Lasi fluids with both lower(28 wt NaCl) and higher (43 wt NaCl) salinity weresampled Mg and SO4 concentrations tend to be zero in thepurest samples at Fatu Kapa But the purest fluids from KuloLasi showed significant levels of Mg and SO4 associated withan extremely acidic pH (lt25) and a high119879 (343∘C) Althoughwe cannot totally discard that some mixing with seawateroccurred endmember concentrations of the Kulo Lasi fluidswere then estimated to be close to the purest fluids sampledwhereas they were obtained from mixing lines at Fatu Kapaassuming Mg zero (Table 5)
Fluids from Fatu Kapa were enriched compared to sea-water in alkali alkaline Earth and transition metals as wellas in strontium bromide and silica Conversely the fluidsfrom Kulo Lasi exhibited a much more complex patternThey were all highly enriched in transition metals and silicacompared to seawater and fluids from Fatu Kapa (eg Fe upto sim10mM) The enrichment versus seawater in alkali metalswas not as striking as for Fatu Kapa fluids As for the alkalineEarth metals the amount of Ca was identical to seawater andfluids were depleted in Sr compared to seawater Finally bothdepletion and enrichment in Br were observed in the fluidsfrom Kulo Lasi
43 Organic Geochemistry First of all we would like to men-tion that because solubility of organic compounds decreaseswith119879 and because samples were processed at room tempera-ture the measured concentrations are probably lower than insitu concentrations Moreover it is very likely that a portionof theOMwas adsorbed on small particles in the fluids whichare not taken into account using our extraction and analyticaltechniques As a result the concentrations we report hereprobably represent lower estimates of in situ concentrationsHowever since in situ measurement techniques are notavailable yet these values are the best estimates we can obtainNote that they also are the first to be published for SVOCs
Formate and acetate reached 163 and 155 120583M respec-tively and covaried withMg in the Kulo Lasi fluids (Figure 4)Concentrations of formate and acetate were significantlyhigher in the Fatu Kapa area but no correlation with Mgcould be observed Nevertheless the purest fluids usuallyshowed the highest concentrations Formate reached 68 ppbat Stephanie and 722 ppb at Fati Ufu whereas it could notbe detected at IdefX and Tutafi and was not measured at
6 GeofluidsTa
ble3Measuredconcentrationof
major
andminor
elem
entsin
hydrotherm
alflu
idsfrom
theKu
loLasiandFatu
Kapa
vent
fieldsFU
X-PL
YY-TiD
ZandFU
X-PL
YY-TiGZarereplicate
samplestakenin
thesam
eorifi
ceone
aftertheo
therbut
using2
individu
alTi
syrin
ges119879m
ax(chimney)isthem
axim
um119879o
fthe
discharged
fluidforthe
givenchim
neyw
hich
wasrecorded
bythe119879
prob
eofthe
subm
arineb
efores
ampling119879m
ax(sam
ple)isthem
axim
um119879o
fthe
fluid
enterin
gthes
ampler
recorded
durin
gsamplingby
thea
uton
omou
ssensorthatw
ascoup
led
atthen
ozzle
ofthes
ampler
Sample
name
Zone
Site
Descriptio
nDepth119879max
(sam
ple)
∘C
119879max
(chimney)
∘C
pHd20
Kgmminus3
S permilNaC
l(w
t)
Cl mM
Si mM
SO4
mM
Br 120583MNa
mM
K mM
Mg
mM
Ca mM
Li 120583MLi 120583M
Rb 120583MSr 120583M
Fe 120583MMn120583M
Cu 120583MZn 120583M
NaCl
BrC
ltimes103
NaK
CH4M
n
IAPS
O-
-Standard
water
--
--
-35
32
546
00
282
839
468
102
532
103
2727
1390ltLO
DltLO
DltLO
DltLO
D09
1546
-FU
-PL-05-
TiG2
KuloLasi
South(out)
Referencew
ater
1150
--
-10
2335
32
551
01
290
833
457
98532
106
2528
44
93ltLO
DltLO
DltLO
DltLO
D083
1547
-
FU-PL-05-
TiG1
KuloLasi
South(in
)Diffusefl
uidabove
worms
1414
328
-596
1023
3532
549
02
293
833
457
99532
106
2852
46
92ltLO
DltLO
D14
15083
1546
-
FU-PL-06-
TiG4
KuloLasi
North
(in)
Beehivetypeb
lack
smoker
1475
1341
332
607
1022
3330
516
10270
822
448
106
498
105
3354
53
84123
3217
31
087
1642
-
FU-PL-06-
TiD4
KuloLasi
North
(in)
Beehivetypeb
lack
smoker
1475
136
332
558
1021
3128
485
21
239
994
406
95457
102
3255
61
7478
7613
15084
20
430010
FU-PL-06-
TiG3
KuloLasi
North
(in)
Translu
cent
smoker
1475
3423
3307
224
1017
3229
497
82
88
738
388
185
246
116
149
156
2673
4796
862
1445
078
1521
0007
FU-PL-06-
TiD3
KuloLasi
North
(in)
Translu
cent
smoker
1475
3377
3307
237
1018
3330
517
84
107
770
405
166
286
108
115149
2494
4283
788
42
41078
1524
-
FU-PL-06-
TiD1
KuloLasi
North
(in)
Blacksm
oker
1475
3432
3451
236
102
4743
735
146
62
1135
612
295
265
109
238
249
4634
9884
1416
25
175
083
1521
-
FU-PL-06-
TiG1
KuloLasi
North
(in)
Blacksm
oker
1475
3432
3451
332
1028
4440
689
108
120
1051
565
237
349
108
176
197
3691
6845
1064
2077
082
1524
0001
FU3-PL
-03-
TiD3
Fatu
Kapa
20masf
Referencew
ater
1488
--
--
-33
565
00
288
841
483
104
545
107
2251
6ltLO
DltLO
DltLO
DltLO
DltLO
D085
1546
-
FU3-PL
-14-
TiG2
Fatu
Kapa
23masf
Referencew
ater
1572
2-
--
3633
557
00
287
841
477
104
542
108
23nm
nmnm
nmnm
nmnm
086
1546
-
FU3-PL
-04-
TiD3
Fatu
Kapa
Stephanie
Translu
cent
smoker
1554
213
279
465
103
4541
704
07
109
1300
519
398
187
696
472
568
80ltLO
D169
166
nmltLO
D074
1813
-
FU3-PL
-04-
TiG3
Fatu
Kapa
Stephanie
Translu
cent
smoker
1554
213
279
464
103
4440
686
10129
1240
513
365
225
628
420
504
71169
nm141
82ltLO
D075
1814
0805
FU3-PL
-08-
TiD1
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
289
280
410
3149
45
770
38
131574
535
542
08
989
705
804
121
268
655
265
66ltLO
D069
20
100886
FU3-PL
-08-
TiG1
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
289
280
341
1031
4945
772
47
07
1592
537
547
05
987
708
807
122
283
167
269
nmltLO
D070
21
100762
FU3-PL
-08-
TiD2
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
291
280
383
1031
4844
748
43
05
1537
520
529
06
953
684
806
116ltLO
D148
259
nmltLO
D070
21
10-
FU3-PL
-09-
TiD2
Fatu
Kapa
Stephanie
Beehivetypeb
lack
smoker
+bacterial
mat
1650
197
236
519
1026
4037
629
17198
1052
500
244
374
378
230
293
36149
nm65
nm10
079
1721
0902
FU3-PL
-09-
TiG2
Fatu
Kapa
Stephanie
Beehivetypeb
lack
smoker
+bacterial
mat
1559
197
236
542
1025
3835
600
10238
959
489
185
443
264
143
193
23ltLO
Dnm
23nmltLO
D081
1626
-
FU3-PL
-06-
TiD1
Fatu
Kapa
Carla
Translu
cent
smoker
1663
278
270
503
1024
3734
576
17185
927
482
285
352
179
260
310
42101
nmnm
nmltLO
D084
1617
-
FU3-PL
-06-
TiG1
Fatu
Kapa
Carla
Translu
cent
smoker
1663
278
270
491
1024
3734
579
07
127
984
476
378
236
222
391
455
63ltLO
D18
32nmltLO
D082
1713
-
FU3-PL
-08-
TiD3
Fatu
Kapa
Carla
Translu
cent
smoker
1664
281
281
278
1024
3835
594
45
11113
9479
596
04
315
690
746
104
115nm
48nm
44
080
198
1365
FU3-PL
-08-
TiG3
Fatu
Kapa
Carla
Translu
cent
smoker
1664
281
281
417
1024
3835
592
40
19112
0477
577
27
303
655
720
96ltLO
D288
39nmltLO
D081
198
-
FU3-PL
-11-
TiD3
Fatu
Kapa
IdefX
Translu
cent
smoker
1573
259
258
49
1025
4137
637
1483
1142
509
498
155
350
541
612
78ltLO
D38
26nmltLO
D080
1810
-
FU3-PL
-11-
TiG3
Fatu
Kapa
IdefX
Translu
cent
smoker
1573
259
258
443
1025
4339
664
41
191268
518
635
20
447
733
802
110160
nm46
nm25
078
198
1848
Geofluids 7
Table3Con
tinued
Sample
name
Zone
Site
Descriptio
nDepth119879max
(sam
ple)
∘C
119879max
(chimney)
∘C
pHd20
Kgmminus3
S permilNaC
l(w
t)
Cl mM
Si mM
SO4
mM
Br 120583MNa
mM
K mM
Mg
mM
Ca mM
Li 120583MLi 120583M
Rb 120583MSr 120583M
Fe 120583MMn120583M
Cu 120583MZn 120583M
NaCl
BrC
ltimes103
NaK
CH4M
n
FU3-PL
-14-
TiD1
Fatu
Kapa
IdefX
Translu
cent
smoker
1572
271
271
373
1025
4339
665
42
111282
519
662
08
434
764
823
120
144
2864
nm34
078
198
1078
FU3-PL
-14-
TiG1
Fatu
Kapa
IdefX
Translu
cent
smoker
1572
271
271
397
1025
4239
661
41
08
1279
515
657
08
429
757
825
119ltLO
Dnm
62nmltLO
D078
198
-
FU3-PL
-14-
TiD2
Fatu
Kapa
ObelX
Translu
cent
smoker
1669
272
-459
103
4945
769
45
07
1506
577
694
13655
757
nmnm
nmnm
nmnm
nm075
20
8-
FU3-PL
-14-
TiD3
Fatu
Kapa
ObelX
Translu
cent
smoker
1636
287
-428
103
4743
729
37
150
1283
557
588
111
650
621
nmnm
nmnm
nmnm
nm076
189
-
FU3-PL
-14-
TiG3
Fatu
Kapa
ObelX
Translu
cent
smoker
1636
287
-537
1028
4339
672
25
270
1103
528
425
253
546
415
nmnm
nmnm
nmnm
nm079
1612
-
FU3-PL
-18-
TiD1
Fatu
Kapa
AsterX
Translu
cent
smoker
1540
265
260
435
1027
4441
693
37
101344
533
649
12511
755
nmnm
nmnm
nmnm
nm077
198
-
FU3-PL
-17-
TiD2
Fatu
Kapa
FatiUfu
Greysm
oker
1522
299
303
426
1031
4743
739
33
931378
555
384
176
666
543
nmnm
nmnm
nmnm
nm075
1914
-
FU3-PL
-17-
TiG2
Fatu
Kapa
FatiUfu
Greysm
oker
1522
299
303
422
1031
4844
748
35
87
1402
562
398
159
697
569
nmnm
nmnm
nmnm
nm075
1914
-
FU3-PL
-21-
TiD1
Fatu
Kapa
FatiUfu
Greysm
oker
1523
302
301
381
1032
5046
784
47
141554
577
473
14862
717
nmnm
nmnm
nmnm
nm074
20
12-
FU3-PL
-21-
TiG1
Fatu
Kapa
FatiUfu
Greysm
oker
1523
302
301
469
103
4541
708
27
105
1292
544
347
193
603
474
nmnm
nmnm
nmnm
nm077
1816
-
FU3-PL
-21-
TiD2
Fatu
Kapa
FatiUfu
Whitesm
oker
1503
-284
327
1028
4441
694
49
04
1359
534
393
10633
573
nmnm
nmnm
nmnm
nm077
20
14-
FU3-PL
-21-
TiG2
Fatu
Kapa
FatiUfu
Whitesm
oker
1503
-284
422
1026
4239
661
39
701217
520
320
133
506
435
nmnm
nmnm
nmnm
nm079
1816
-
FU3-PL
-20-
TiD1
Fatu
Kapa
Tutafi
Greysm
oker
1580
316
317
41
1029
4642
720
26
06
1409
543
546
09
654
628
nmnm
nmnm
nmnm
nm075
20
10-
FU3-PL
-20-
TiG1
Fatu
Kapa
Tutafi
Greysm
oker
1580
316
317
414
1029
4642
723
23
101409
543
547
07
664
630
nmnm
nmnm
nmnm
nm075
1910
-
FU3-PL
-21-
TiD3
Fatu
Kapa
Tutafi
Whitesm
oker
1626
293
294
292
1028
4541
701
51
09
1367
528
513
03
639
640
nmnm
nmnm
nmnm
nm075
1910
-
FU3-PL
-21-
TiG3
Fatu
Kapa
Tutafi
Whitesm
oker
1626
293
294
365
1027
4541
700
50
08
1371
528
510
08
633
633
nmnm
nmnm
nmnm
nm075
20
10-
8 Geofluids
Table4
Measuredgascon
centratio
nandassociated
stableiso
topicratiosh
ydrothermalflu
idsfromtheK
uloL
asiand
FatuKa
paventfieldsVa
luesoflogfH2werec
alculated
usingS
UPC
RT92
with
thes
lop9
8database
Samplen
ame
Site
H2S
N2
3He
RRa
H2
logfH2
CH4
CO2
C 2H6
C 2H4
C 3H8
C 3H6
n-C 4
H10n-C 5
H12120575D(H2)120575D(C
H4)12057513C(C
O2)12057513C(C
H4)12057513C(C2H6)12057513C(C3H8)12057513C(C4H10)
mM
mM
mM
mM
mM
mM120583M120583M120583M120583M120583M
120583M
permilpermil
permilpermil
permilpermil
permilSeaw
ater
059
nmnmltLO
D-ltLO
D23
nmnm
nmnm
nmnm
nmnm
nmnm
nmnm
nmFU
-PL-05-TiG1
KuloLasi
012
nmnmltLO
Q-
0001
26ltLO
DnmltLO
DnmltLO
DltLO
Dnm
nmnm
nmnm
nmnm
FU-PL-06-TiD
4Ku
loLasi
166
010
nmnm
114
-0001
13002
0005
000
6000
40005
0005minus323
nm
minus32
minus29
minus27
minus26
nmFU
-PL-06-TiG3
KuloLasi
505
143
nmnm
198minus311
000
651
011
004
20028
0030
0024
000
6minus306
nm
minus41
minus23
minus26
minus26
minus24
FU-PL-06-TiD
1Ku
loLasi
039
248
nmnm
618minus362
000
430
01
0017
0017
0020
0012
000
4minus300
nm
minus19
minus28
minus24
minus26
minus24
FU-PL-06-TiG1
KuloLasi
079
nmnm
104minus440
0001
10002
000
90005
0007
0005
0001minus316
nm
minus02
minus272
minus22
minus26
minus24
FU3-PL
-04-TiG3
Stephanie
091
09311119864minus08
86
003minus18
70114
155ltLO
DltLO
DltLO
DltLO
DltLO
D17
nmnm
nmnm
nmnm
nmFU
3-PL
-08-TiD1
Stephanie
123
198
nm006minus15
70235
290ltLO
DltLO
DltLO
DltLO
DltLO
D32minus676minus108
minus5
minus217
nmnm
nmFU
3-PL
-08-TiG1
Stephanie
098
24744119864minus09
76005minus16
50205
257ltLO
DltLO
DltLO
DltLO
DltLO
D29
nmnm
nmnm
nmnm
nmFU
3-PL
-09-TiD2
Stephanie
023
04819119864minus09
70004minus17
50059
60ltLO
DltLO
DltLO
DltLO
DltLO
D07minus436minus111
minus53
minus222
nmnm
nmFU
3-PL
-06-TiD1
Carla
134
05071119864minus09
96001minus235
0021
45ltLO
DltLO
DltLO
DltLO
DltLO
D05
nmnm
nmnm
nmnm
nmFU
3-PL
-08-TiD3
Carla
019
33317119864minus08
98005minus16
5006
6119ltLO
DltLO
DltLO
DltLO
DltLO
D15
minus410minus109
minus47
minus215
nmnm
nmFU
3-PL
-11-T
iG3
Idef
X113
07818119864minus08
98003minus18
70085
100ltLO
DltLO
DltLO
DltLO
DltLO
D11
nmnm
nmnm
nmnm
nmFU
3-PL
-14-TiD1
Idef
X10
012
055119864minus09
87
002minus205
0069
101ltLO
DltLO
DltLO
DltLO
DltLO
D11
minus417minus110
minus49
minus238
nmnm
nmFU
3-PL
-14-TiD2
ObelX
085
10538119864minus08
98003minus18
70110
87ltLO
DltLO
DltLO
DltLO
DltLO
D10
minus40
7minus113
minus5
minus24
nmnm
nmFU
3-PL
-14-TiD3
ObelX
054
09352119864minus09
84
002minus205
0165
92ltLO
DltLO
DltLO
DltLO
DltLO
D10
nmnm
nmnm
nmnm
nmFU
3-PL
-18-TiD1
AsterX
098
089
nmnm
001minus235
0067
92ltLO
DltLO
DltLO
DltLO
DltLO
D10
minus412minus111
minus49
minus236
nmnm
nmFU
3-PL
-17-TiG2
FatiUfu
176
08427119864minus08
99001minus259
0070
215ltLO
DltLO
DltLO
DltLO
DltLO
D23
-minus93
minus23
minus61
nmnm
nmFU
3-PL
-21-T
iD2
FatiUfu
071
20731119864minus09
99003minus211
0111
126ltLO
DltLO
DltLO
DltLO
DltLO
D15
minus410minus109
minus44
minus233
nmnm
nmFU
3-PL
-20-TiD1
Tutafi
236
11814119864minus08
92005minus18
90156
222ltLO
DltLO
DltLO
DltLO
DltLO
D24minus396minus111
minus45
minus236
nmnm
nmFU
3-PL
-21-T
iD3
Tutafi
084
167
nmnm
003minus211
0053
117ltLO
DltLO
DltLO
DltLO
DltLO
D14
minus415minus109
minus47
minus242
nmnm
nm
Geofluids 9
Table5En
dmem
bercom
positions
influ
idsfrom
theK
uloLasiandFatu
Kapa
vent
fieldsKu
loLasiendm
emberscann
otbe
extrapolated
atMg=
0Va
luespresentedhereforb
othbrinea
ndcond
ensedvapo
urph
ases
correspo
ndto
concentrations
inthefl
uidwith
thelow
estM
gElem
entalcom
positions
inendm
emberfl
uids
from
thev
arious
sites
oftheF
atuKa
pavent
field
were
calculated
usingthem
ixinglin
es(FigureS
1)andassumingMg=0Va
lues
ofthep
urestfl
uidwereu
sedwhenlin
earregressionwas
notp
ossib
le(lowast)Notethato
nlyon
esam
plew
asavailable
forthe
AsterX
site(1)
Zone
Site
Depth119879
pHNaC
lCl
SiSO
4Br
Na
KMg
CaLi
RbSr
FeMn
CuZn
NaCl
BrC
lNaK
CH4Mn
∘ C(w
t)
mM
mM
mM120583M
mM
mM
mM
mM120583M120583M120583M
120583M120583M
120583M120583M
times103
KuloLasi
NaC
lpoo
r1475
345
224
29
497
82
88
738
388
185
246
116
149
2673
4796
862
1445
078
148
210007lowast
KuloLasi
NaC
lrich
1475
345
236
43
735
146
62
1135
612
295
265
109
238
4634
9884
1416
25
175
083
154
210001lowast
Fatu
Kapa
Stephanie
1555
280
34
45
767
47lowast
00
1569
532
545
00
989
708
114282lowast
655lowast
268
66lowastltL
OD
069
205
10076lowast
Fatu
Kapa
Carla
1664
280
28
35
594
43
00
1132
477
599
00
314
691
105
114lowast
287lowast
53nm
44lowast
080
190
813
7lowast
Fatu
Kapa
Idef
X1572
270
37
39
665
42lowast
00
1282
518
664
00
443
751
113
160lowast
28lowast
60nm
34lowast
078
193
810
8lowast
Fatu
Kapa
ObelX
1669
270
46
45
771
46
00
1458
580
710
00
859
777
nmnm
nmnm
nmnm
075
189
8-
Fatu
Kapa
AsterX(1)
1540
265
44
41
693
37
101344
533
649
12511
755
nmnm
nmnm
nmnm
077
194
8-
Fatu
Kapa
FatiUfu
1523
300
38
46
790
49
00
1589
580
482
00
854
722
nmnm
nmnm
nmnm
073
201
12-
Fatu
Kapa
FatiUfu
1503
280
33
41
700
49
00
1380
538
400
00
650
583
nmnm
nmnm
nmnm
077
197
13-
Fatu
Kapa
Tutafi
1580
315
41
42
713
51
00
1405
535
529
00
651
635
nmnm
nmnm
nmnm
075
197
10-
IAPS
OStandard
sw-
--
32
546
00
282
839
468
102
532
103
2713
90ltLO
DltLO
DltLO
DltLO
D09
1546
-Ku
loLasi
References
w1150
--
32
551
01
290
833
457
98532
106
2544
93ltLO
DltLO
DltLO
DltL
OD
083
1547
-Fatu
Kapa
References
w1488
--
33
565
00
288
841
483
104
545
107
2258ltLO
DltLO
DltLO
DltLO
DltL
OD
085
1546
-Fatu
Kapa
References
w1572
2-
33
557
00
287
841
477
104
542
108
23nm
nmnm
nmnm
nm086
1546
-lowastMaxim
umvaluew
henlin
earregressionwas
notp
ossib
le(1)on
lyon
esam
ple
10 Geofluids
(a)
(b)
(c)
Figure 3 (a) and (b) Photographs of anhydrite structures observed at Stephanie Carla IdefX AsterX and ObelX site (c) Photographs of greysmokers associated with sulphides structures observed at Fati Ufu and Tutafi Copyrights from Ifremer FUTUNA 3 cruise
02468
1012141618
0 10 20 30 40 50 60Mg (mM)
Kulo Lasi
AcetateFormate
SW-acetateSW-formate
Con
cent
ratio
n(
M)
Figure 4 Mixing lines of formate and acetate versus Mg for the Kulo Lasi fluids Note that the reference deep-sea water sample (FU-PL05-TiG2 noted as SW here) was taken at 1150m depth above the southern wall of the caldera (see Figure 1 for location and Table 3) and thus verylikely within the plume [7] This would account for the unusual concentrations of formate and acetate detected
Geofluids 11
Carla Acetate was detected in all analysed samples andconcentrations were an order of magnitude higher than theones of formate (543ndash2309 ppb) (Table 6)
Heavier extractable organic compounds were notdetected in the dry control experiment and only a few weredetectable but below limit of quantification (LOQ) in theMQ water blank experiment (Table 6) This showed thatsample preparation and storage could be considered ascontamination-free steps The levels of heavier extractableorganic compounds appeared rather high in the referencewater at Fatu Kapa certainly because of the overall spreadhydrothermal discharges and diffuse venting in the region [7](Table 6 Figure 5) This sample was indeed taken mid-waybetween ObelX and AsterX fields at about 20m above theseafloor As a consequence it is difficult to assess possiblecontamination originating from sampling device or seawatercontribution in the present case However earlier studieshave shown that they generally did not represent majorsources of contamination as for the studied compounds[27 37] Nevertheless in comparison to deep-sea waterboth the qualitative (Kulo Lasi) and quantitative (FatuKapa) data obtained suggested enrichment of the fluidsin hydrothermally derived compounds namely n-alkanes(C9ndashC12) n-FAs (C9 C12 C14ndashC18) and PAHs (fluorenephenanthrene pyrene) ([39] Table 6 Figures 5 and 6)Such enrichment was unclear for gtC12 n-alkanes C10C11 C13 n-FAs BTEXs naphthalene acenaphthene andfluoranthene because of their very low concentration andorthe measurement uncertainty
Differences in concentrations seemed to exist among thevents over the Fatu Kapa area Fluids from the Stephanie ventfield had concentrations in hydrocarbons equal or below thereference water sample whereas they were clearly enrichedin C9 C12 C14ndashC18 n-FAs The Carla fluids were slightlyenriched in C9ndashC12 n-alkanes and showed the highest con-centrations in PAHs Fluids from IdefX Fati Ufu and Tutafishared some similarities a strong enrichment in decane andundecane alike concentrations in PAHs and the presence ofsignificant amounts of xylene However fluids expelled at theTutafi vent appeared the most enriched in C9ndashC11 n-alkanesand xylenes In terms of fatty acids and considering theanalytical error the 5 vents showed consistent concentrationswith C9 C16 and C18 being major Note that fluids from FatiUfu seemed depleted in C17 and C18
Generally we did not observe strong linear correlationbetween the concentration of individual compounds andMgNonetheless these relations showed that both enrichmentand depletion of organic compounds seemed to occur inhydrothermal fluids versus deep-sea water
5 Discussion
The elemental and gas composition of hydrothermal fluidsis mainly affected by waterrock interactions and thus thenature of the host rocks phase separation magmatic fluidcontribution conductive cooling and seawater mixing inlocal recharge zones [45] In the following discussion weattempt to unravel the occurrence of these various processes
both at Kulo Lasi and at Fatu Kapa Much less is known onprocesses that control organic geochemistry and are thereforediscussed here as well as some implications of the presenceof organic compounds in hydrothermal fluids Implicationsrelated to the composition of the fluids are dependent onfluxes therefore we give here an attempt to provide order ofmagnitude estimates of heat and mass fluxes
51 Plume-Fluids Relations The geochemistry and dynamicsof the plumes over the Wallis and Futuna region havebeen studied elsewhere [7] The Kulo Lasi plume has beenproposed to be the result of both high-119879 and diffuse ventingfrom multiple vents located both on the floor and on thewall of the caldera Consistently both types of venting havebeen observed [6] Helium nephelometry and Mn profilesrecorded above the northern sampling area showed constantelevated concentrations in the 300masf and were assumedto be the results of diffuse venting Our results show thatthey are obviously the result of the numerous small blacksmokers observed on the seafloor (Figure 2) The methaneconcentration in the sampled fluids was extremely low whichcannot account for the elevated concentration of CH4 inthe water column reported by Konn et al [7] The strongdifference in the CH4Mn ratios between the plume (07ndash45)and the sampled fluids (0001ndash001) is another line of evidencethat the methane plume has another origin compared tohydrothermal fluids and likely come from degassing of thelava flows as suggested by the authors Although other fluiddischarges likely remain undiscovered this is consistent witha past eruption and accumulation of the water mass in thecaldera [39]
A great diversity of the fluid compositions was expectedfrom the geological settings and the water column survey andwas indeed confirmed by the mixing lines that point to asmany endmembers as sampled areas (Figure S1) CH4TDMratios also differed among the vents but it was not due to soleCH4 concentration variations as suggested earlier (Table 5)[7] Finally the very weak nephelometry of the Fatu Kapaplume is likely best explained by the low metal contents ofthe fluids
52 Reaction Zone Depth The solubility of Quartz in hydro-thermal fluids has been studied by different authors (eg[46]) According to these works silica concentration in thefluid may be used to estimate the depth of the reaction zoneThe silica concentration measured in the Kulo Lasi and FatuKapa fluids indicates a hydrothermal reaction zone at seaflooror in thewater column (Figure S2) Both observations suggestthat in this area fluids are not in equilibria with Quartz atthe pressure and temperature of the fluid emission And thisprevents using Si as a geothermometer to determine the depthof the reaction zone
All fluids at Fatu Kapa were indeed highly depleted inSi with respect to the Quartz saturation curve at 170 bar300∘C (Si sim12mM in Figure S2) A higher temperature inthe reaction zone (gt350∘C at 200 bar) may explain a lower Siconcentration in the fluid at equilibrium as Quartz solubilitydecreases (Figure S2) The dispersion of a great number of
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Figure 1 Bathymetric map of the study area Close-ups of Fatu Kapa and Kulo Lasi are shown in boxes where sample positions are markedwith red disks Copyrights from Ifremer FUTUNA 1 2 and 3 cruises
32 Inorganic Geochemistry Sample Preparation and Anal-yses pH was measured using a combined glass electrode(Ecotrode Plus Metrohm) Clminus and H2S were measured bypotentiometry using AgNO3 (005M) and HgCl2 (001M) astitrating solutions respectivelyNaOH (2M)was added to thealiquot before H2S measurement SO4 Br Na K Mg Ca Liand Cl were measured by ionic chromatography (Dionex IonChromatograph System 2000) after appropriate dilutions FeMn Cu Zn Sr Li and Rb were measured by flame atomicabsorption spectrometry using standard additions (AAnalystPerkin Elmer Inc) Aliquots for silica determination wereimmediately diluted 100- to 200-fold and analysed by thesilicomolybdate automatic colorimetric method [42 43]
33 Organic Geochemistry Total Organic Carbon (TOC)was measured using a multi NC 3100 (Analytik Jena AGGermany) Samples were acidified online with HCl and thenpurged with O2 to remove inorganic carbon (IC) A TIC
control analysis was performed and followed by three TOCmeasurements on each sample
Acetate and formate concentrations were determinedusing a Dionex ICS-2000 Reagent-Free Ion Chromatogra-phy System equipped with an AS50 autosampler (DionexCamberley UK) Chromatographic separationwas conductedusing two Ionpac AS15 columns in series at 30∘C and thedetermination of species was carried out using an AnionSelf-Regenerating Suppressor (ASRS 300 4mm) unit in com-bination with a DS6 heated conductivity cell (35∘C) Thegradient program was as follows 6mmol Lminus1 KOH (43min)increase from 27mmol Lminus1 KOH minminus1 to 60mmol Lminus1(39min) decrease from 54mmol Lminus1 KOHminminus1 to 6mmolLminus1 (5min)
SVOCs were extracted using Stir Bar Sorptive Extraction(SBSE) Basically any compound with a log Kow gt 25 isrecovered with a rate gt 50 [44] The method was improvedafter Konn et al [37] The entire content of the titanium
4 Geofluids
Table 1 Main GC analytical parameters used for calibration and analyses of hydrothermal fluid samples Each group of compounds (n-alkanes BTEXs PAHs and n-fatty acids) was analysed using separate twisters
n-Alkanes BTEX amp PAHs n-Fatty acidsOvenInitial 119879 (∘C) 40 40 40Initial 119905 (min) 1 1 1ramp 40 to 320∘C at 12∘Cmin 40 to 320∘C at 12∘Cmin 40 to 320∘C at 20∘CminFinal 119879 (∘C) 320 320 320Final 119905 (min) 2 2 2Injector119879 (∘C) 250 250 325
Table 2 Experimental conditions used for calibration curves Linear regressions were performed on one order of magnitude concentrationdomain depending on the concentration range of the samples
syringe was transferred into a precombusted glass bottle andsix 90mL aliquots of the sample were poured into 100mLprecombusted glass vials 10mL ofMeOHwas added to avoidadsorption of the compounds onto the wall of the vialsInternal standards were added to the solutions in 2012 so thatquantification could only be achieved in Fatu Kapa fluidsExtraction was performed in sealed vials with ultrainertseptum crimps at 300 rpm and using 48 120583L PDMS Twisters(Gerstel GmbH) We focused on a selection of chemicalgroups that had previously been described as hydrothermallyderived [27] To that respect pairs of aliquots were dedicatedto analysis of n-alkanes n-FAs and both BTEXs and PAHsrespectively Extraction kinetics experiments showed thatchemical equilibrium was reached after 5 h of extraction forn-alkanes 4 h for PAHs and 14 h for n-FAs (Konn unpub-lished results) Twisters were then removed rinsed with MQwater dried and stored at +4∘C until analyses by ThermalDesorption-Gas Chromatography-Mass Spectrometry (TD-GC-MS) [37] Analytical parameters were adjusted for eachgroup of compounds (Table 1)
For each batch of conditioned Twisters one was sparedstored at +4∘C and analysed in the same run as the otherTwistersThis dry blank aimed at showing any contaminationthat could have occurred during conditioning storage andtransport MQ water samples were prepared and extractedon board as regular hydrothermal samples to check if anycontaminations could have occurred during the samplepreparation step Deep-sea water was also collected pro-cessed and analysed using the same titanium syringes andaccording to the same protocols as for hydrothermal fluidsamples and thus constitute the reference blank experiment
Calibration was achieved using a commercial stan-dard solution of BTEXs and 3 custom standard solu-tions of C9ndashC20 n-alkanes C6ndashC18 n-FAs and PAHs con-taining naphthalene (N) Acenaphtene (A) Fluorene (F)Phenanthrene (Ph) Anthracene (An) Fluoranthene (Fl)and pyrene (Py) (LGC Standards LGC Ltd) Deuteratedn-alkanes (C10D22 and C14D34) methyl esters (C9H18O2
and C15H30O2) and deuterated PAHs (naphthalene-D8Biphenyl-D8 and Phenanthrene-D10) were used as inter-nal standards (IS) Calibration curves (Concentration (ana-lyte)Concentration (IS) versus Area (analyte)Area (IS))were obtained using at least five concentration levels thatwere replicated 3 times (Table 2) Although the correlationcoefficient of the linear regressions was satisfactory for allcompounds the significance and lack of fit of the modelwere checked by statistical tests before validation A series ofStudent Barlett Chi-square and Fisher tests was run for eachindividual compound using the Lumiere software The bestfitting model was then chosen for each case and confidenceintervals were calculated
4 Results
Altogether 35 hot fluid samples were collected in the studyarea from 8 different sites Kulo Lasi caldera (6) on theone hand and Stephanie (7) Carla (4) IdefX (4) ObelX (3)AsterX (1) Fati Ufu (6) and Tutafi (4) on the other handall located in the Fatu Kapa area (Figure 1) The KuloLasi smokers occurred at sim1500m depth on recent lavaflows and consisted in a multitude of short (sim25 cm) andnarrow (sim3ndash5 cm) diameter anhydrite chimneys containing asmall percentage of sphalerite (ZnS) chalcopyrite (CuFeS2)isocubanite (CuFe2S3) pyrrhotite (Fe1minus119909S) and pyrite (FeS2)(Figure 2)The temperature was consistently about 343∘C andthe pH approached 22ndash23 (Table 3) In the FatuKapa area wecould distinguish two types of hydrothermal environments at1550ndash1650m depth Translucent 270ndash290∘C fluids associatedwith anhydrite chimneys (up to 25m tall and 25m indiameter) characterised Stephanie Carla IdefX ObelX andAsterX sites while gt300∘C milky to grey fluids associatedwith sulphide chimneys were characteristic of the southwestregion including Fati Ufu and Tutafi sites (Figure 3 Table 3)
41 Gas Concentrations of gases in all fluids as well as stableisotopes data are compiled in Table 4 Samples recovered
Geofluids 5
Figure 2 Photographs of sulphide chimneys and young lava flowsobserved on the floor of the Kulo Lasi caldera Copyrights fromIfremer FUTUNA 1 cruise
from Kulo Lasi were extremely poor in CH4 (lt001mM) butcontained the series of C2ndashC5 hydrocarbons Samples fromFatuKapa had higher concentration of CH4 (005ndash0235mM)but only n-pentane (05ndash32 120583M) could be detected andquantified in terms of longer hydrocarbons One samplefrom Kulo Lasi was found to be extremely rich in H2 withnearly 20mM while the others ranged from 1 to 6mM andwere below 005mM at Fatu Kapa H2S was highly variablebetween the 3 sampled chimneys at Kulo Lasi (039 166 and505mM) while it was found rather homogeneous at FatuKapa with values around 1mM CO2 concentrations weremore elevated at Fatu Kapa (45ndash29mM) compared to KuloLasi (1ndash5mM)
Helium isotope ratios were in the range 70ndash99 Ra overthe Fatu Kapa area in agreement with plume data [7] Theycould not be measured at Kulo Lasi unfortunately Carbonisotopes ratios were around minus5permil for CO2 at Fatu Kapawhereas at Kulo Lasi the ratio showed very different results
ranging from minus02 to minus41permil As for methane 12057513C wereslightly lower at Kulo Lasi (simminus28permil) versus Fatu Kapa (simminus23permil) and 120575D was about minus110permil in all samples from FatuKapa 120575D (CH4) could not bemeasured in theKulo Lasi fluidsbecause of the too low concentrations of CH4 Carbon isotoperatios of longer hydrocarbons were in the minus27 to minus22permil atboth vent fields To be noted one sample from Fati Ufu in theFatu Kapa area showed remarkably lower isotopic ratios with12057513C (CO2) = minus23permil 12057513C (CH4) = minus61permil and 120575D (CH4) =minus93permil We do not have any explanation for this but do nothave any reasons either to consider it as an outlier
42 Major and Minor Elements Major and minor elementsmeasurements data are compiled in Table 3 Fluids fromFatu Kapa all exhibited a higher salinity than seawater up to46 wt NaCl whereas at Kulo Lasi fluids with both lower(28 wt NaCl) and higher (43 wt NaCl) salinity weresampled Mg and SO4 concentrations tend to be zero in thepurest samples at Fatu Kapa But the purest fluids from KuloLasi showed significant levels of Mg and SO4 associated withan extremely acidic pH (lt25) and a high119879 (343∘C) Althoughwe cannot totally discard that some mixing with seawateroccurred endmember concentrations of the Kulo Lasi fluidswere then estimated to be close to the purest fluids sampledwhereas they were obtained from mixing lines at Fatu Kapaassuming Mg zero (Table 5)
Fluids from Fatu Kapa were enriched compared to sea-water in alkali alkaline Earth and transition metals as wellas in strontium bromide and silica Conversely the fluidsfrom Kulo Lasi exhibited a much more complex patternThey were all highly enriched in transition metals and silicacompared to seawater and fluids from Fatu Kapa (eg Fe upto sim10mM) The enrichment versus seawater in alkali metalswas not as striking as for Fatu Kapa fluids As for the alkalineEarth metals the amount of Ca was identical to seawater andfluids were depleted in Sr compared to seawater Finally bothdepletion and enrichment in Br were observed in the fluidsfrom Kulo Lasi
43 Organic Geochemistry First of all we would like to men-tion that because solubility of organic compounds decreaseswith119879 and because samples were processed at room tempera-ture the measured concentrations are probably lower than insitu concentrations Moreover it is very likely that a portionof theOMwas adsorbed on small particles in the fluids whichare not taken into account using our extraction and analyticaltechniques As a result the concentrations we report hereprobably represent lower estimates of in situ concentrationsHowever since in situ measurement techniques are notavailable yet these values are the best estimates we can obtainNote that they also are the first to be published for SVOCs
Formate and acetate reached 163 and 155 120583M respec-tively and covaried withMg in the Kulo Lasi fluids (Figure 4)Concentrations of formate and acetate were significantlyhigher in the Fatu Kapa area but no correlation with Mgcould be observed Nevertheless the purest fluids usuallyshowed the highest concentrations Formate reached 68 ppbat Stephanie and 722 ppb at Fati Ufu whereas it could notbe detected at IdefX and Tutafi and was not measured at
6 GeofluidsTa
ble3Measuredconcentrationof
major
andminor
elem
entsin
hydrotherm
alflu
idsfrom
theKu
loLasiandFatu
Kapa
vent
fieldsFU
X-PL
YY-TiD
ZandFU
X-PL
YY-TiGZarereplicate
samplestakenin
thesam
eorifi
ceone
aftertheo
therbut
using2
individu
alTi
syrin
ges119879m
ax(chimney)isthem
axim
um119879o
fthe
discharged
fluidforthe
givenchim
neyw
hich
wasrecorded
bythe119879
prob
eofthe
subm
arineb
efores
ampling119879m
ax(sam
ple)isthem
axim
um119879o
fthe
fluid
enterin
gthes
ampler
recorded
durin
gsamplingby
thea
uton
omou
ssensorthatw
ascoup
led
atthen
ozzle
ofthes
ampler
Sample
name
Zone
Site
Descriptio
nDepth119879max
(sam
ple)
∘C
119879max
(chimney)
∘C
pHd20
Kgmminus3
S permilNaC
l(w
t)
Cl mM
Si mM
SO4
mM
Br 120583MNa
mM
K mM
Mg
mM
Ca mM
Li 120583MLi 120583M
Rb 120583MSr 120583M
Fe 120583MMn120583M
Cu 120583MZn 120583M
NaCl
BrC
ltimes103
NaK
CH4M
n
IAPS
O-
-Standard
water
--
--
-35
32
546
00
282
839
468
102
532
103
2727
1390ltLO
DltLO
DltLO
DltLO
D09
1546
-FU
-PL-05-
TiG2
KuloLasi
South(out)
Referencew
ater
1150
--
-10
2335
32
551
01
290
833
457
98532
106
2528
44
93ltLO
DltLO
DltLO
DltLO
D083
1547
-
FU-PL-05-
TiG1
KuloLasi
South(in
)Diffusefl
uidabove
worms
1414
328
-596
1023
3532
549
02
293
833
457
99532
106
2852
46
92ltLO
DltLO
D14
15083
1546
-
FU-PL-06-
TiG4
KuloLasi
North
(in)
Beehivetypeb
lack
smoker
1475
1341
332
607
1022
3330
516
10270
822
448
106
498
105
3354
53
84123
3217
31
087
1642
-
FU-PL-06-
TiD4
KuloLasi
North
(in)
Beehivetypeb
lack
smoker
1475
136
332
558
1021
3128
485
21
239
994
406
95457
102
3255
61
7478
7613
15084
20
430010
FU-PL-06-
TiG3
KuloLasi
North
(in)
Translu
cent
smoker
1475
3423
3307
224
1017
3229
497
82
88
738
388
185
246
116
149
156
2673
4796
862
1445
078
1521
0007
FU-PL-06-
TiD3
KuloLasi
North
(in)
Translu
cent
smoker
1475
3377
3307
237
1018
3330
517
84
107
770
405
166
286
108
115149
2494
4283
788
42
41078
1524
-
FU-PL-06-
TiD1
KuloLasi
North
(in)
Blacksm
oker
1475
3432
3451
236
102
4743
735
146
62
1135
612
295
265
109
238
249
4634
9884
1416
25
175
083
1521
-
FU-PL-06-
TiG1
KuloLasi
North
(in)
Blacksm
oker
1475
3432
3451
332
1028
4440
689
108
120
1051
565
237
349
108
176
197
3691
6845
1064
2077
082
1524
0001
FU3-PL
-03-
TiD3
Fatu
Kapa
20masf
Referencew
ater
1488
--
--
-33
565
00
288
841
483
104
545
107
2251
6ltLO
DltLO
DltLO
DltLO
DltLO
D085
1546
-
FU3-PL
-14-
TiG2
Fatu
Kapa
23masf
Referencew
ater
1572
2-
--
3633
557
00
287
841
477
104
542
108
23nm
nmnm
nmnm
nmnm
086
1546
-
FU3-PL
-04-
TiD3
Fatu
Kapa
Stephanie
Translu
cent
smoker
1554
213
279
465
103
4541
704
07
109
1300
519
398
187
696
472
568
80ltLO
D169
166
nmltLO
D074
1813
-
FU3-PL
-04-
TiG3
Fatu
Kapa
Stephanie
Translu
cent
smoker
1554
213
279
464
103
4440
686
10129
1240
513
365
225
628
420
504
71169
nm141
82ltLO
D075
1814
0805
FU3-PL
-08-
TiD1
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
289
280
410
3149
45
770
38
131574
535
542
08
989
705
804
121
268
655
265
66ltLO
D069
20
100886
FU3-PL
-08-
TiG1
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
289
280
341
1031
4945
772
47
07
1592
537
547
05
987
708
807
122
283
167
269
nmltLO
D070
21
100762
FU3-PL
-08-
TiD2
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
291
280
383
1031
4844
748
43
05
1537
520
529
06
953
684
806
116ltLO
D148
259
nmltLO
D070
21
10-
FU3-PL
-09-
TiD2
Fatu
Kapa
Stephanie
Beehivetypeb
lack
smoker
+bacterial
mat
1650
197
236
519
1026
4037
629
17198
1052
500
244
374
378
230
293
36149
nm65
nm10
079
1721
0902
FU3-PL
-09-
TiG2
Fatu
Kapa
Stephanie
Beehivetypeb
lack
smoker
+bacterial
mat
1559
197
236
542
1025
3835
600
10238
959
489
185
443
264
143
193
23ltLO
Dnm
23nmltLO
D081
1626
-
FU3-PL
-06-
TiD1
Fatu
Kapa
Carla
Translu
cent
smoker
1663
278
270
503
1024
3734
576
17185
927
482
285
352
179
260
310
42101
nmnm
nmltLO
D084
1617
-
FU3-PL
-06-
TiG1
Fatu
Kapa
Carla
Translu
cent
smoker
1663
278
270
491
1024
3734
579
07
127
984
476
378
236
222
391
455
63ltLO
D18
32nmltLO
D082
1713
-
FU3-PL
-08-
TiD3
Fatu
Kapa
Carla
Translu
cent
smoker
1664
281
281
278
1024
3835
594
45
11113
9479
596
04
315
690
746
104
115nm
48nm
44
080
198
1365
FU3-PL
-08-
TiG3
Fatu
Kapa
Carla
Translu
cent
smoker
1664
281
281
417
1024
3835
592
40
19112
0477
577
27
303
655
720
96ltLO
D288
39nmltLO
D081
198
-
FU3-PL
-11-
TiD3
Fatu
Kapa
IdefX
Translu
cent
smoker
1573
259
258
49
1025
4137
637
1483
1142
509
498
155
350
541
612
78ltLO
D38
26nmltLO
D080
1810
-
FU3-PL
-11-
TiG3
Fatu
Kapa
IdefX
Translu
cent
smoker
1573
259
258
443
1025
4339
664
41
191268
518
635
20
447
733
802
110160
nm46
nm25
078
198
1848
Geofluids 7
Table3Con
tinued
Sample
name
Zone
Site
Descriptio
nDepth119879max
(sam
ple)
∘C
119879max
(chimney)
∘C
pHd20
Kgmminus3
S permilNaC
l(w
t)
Cl mM
Si mM
SO4
mM
Br 120583MNa
mM
K mM
Mg
mM
Ca mM
Li 120583MLi 120583M
Rb 120583MSr 120583M
Fe 120583MMn120583M
Cu 120583MZn 120583M
NaCl
BrC
ltimes103
NaK
CH4M
n
FU3-PL
-14-
TiD1
Fatu
Kapa
IdefX
Translu
cent
smoker
1572
271
271
373
1025
4339
665
42
111282
519
662
08
434
764
823
120
144
2864
nm34
078
198
1078
FU3-PL
-14-
TiG1
Fatu
Kapa
IdefX
Translu
cent
smoker
1572
271
271
397
1025
4239
661
41
08
1279
515
657
08
429
757
825
119ltLO
Dnm
62nmltLO
D078
198
-
FU3-PL
-14-
TiD2
Fatu
Kapa
ObelX
Translu
cent
smoker
1669
272
-459
103
4945
769
45
07
1506
577
694
13655
757
nmnm
nmnm
nmnm
nm075
20
8-
FU3-PL
-14-
TiD3
Fatu
Kapa
ObelX
Translu
cent
smoker
1636
287
-428
103
4743
729
37
150
1283
557
588
111
650
621
nmnm
nmnm
nmnm
nm076
189
-
FU3-PL
-14-
TiG3
Fatu
Kapa
ObelX
Translu
cent
smoker
1636
287
-537
1028
4339
672
25
270
1103
528
425
253
546
415
nmnm
nmnm
nmnm
nm079
1612
-
FU3-PL
-18-
TiD1
Fatu
Kapa
AsterX
Translu
cent
smoker
1540
265
260
435
1027
4441
693
37
101344
533
649
12511
755
nmnm
nmnm
nmnm
nm077
198
-
FU3-PL
-17-
TiD2
Fatu
Kapa
FatiUfu
Greysm
oker
1522
299
303
426
1031
4743
739
33
931378
555
384
176
666
543
nmnm
nmnm
nmnm
nm075
1914
-
FU3-PL
-17-
TiG2
Fatu
Kapa
FatiUfu
Greysm
oker
1522
299
303
422
1031
4844
748
35
87
1402
562
398
159
697
569
nmnm
nmnm
nmnm
nm075
1914
-
FU3-PL
-21-
TiD1
Fatu
Kapa
FatiUfu
Greysm
oker
1523
302
301
381
1032
5046
784
47
141554
577
473
14862
717
nmnm
nmnm
nmnm
nm074
20
12-
FU3-PL
-21-
TiG1
Fatu
Kapa
FatiUfu
Greysm
oker
1523
302
301
469
103
4541
708
27
105
1292
544
347
193
603
474
nmnm
nmnm
nmnm
nm077
1816
-
FU3-PL
-21-
TiD2
Fatu
Kapa
FatiUfu
Whitesm
oker
1503
-284
327
1028
4441
694
49
04
1359
534
393
10633
573
nmnm
nmnm
nmnm
nm077
20
14-
FU3-PL
-21-
TiG2
Fatu
Kapa
FatiUfu
Whitesm
oker
1503
-284
422
1026
4239
661
39
701217
520
320
133
506
435
nmnm
nmnm
nmnm
nm079
1816
-
FU3-PL
-20-
TiD1
Fatu
Kapa
Tutafi
Greysm
oker
1580
316
317
41
1029
4642
720
26
06
1409
543
546
09
654
628
nmnm
nmnm
nmnm
nm075
20
10-
FU3-PL
-20-
TiG1
Fatu
Kapa
Tutafi
Greysm
oker
1580
316
317
414
1029
4642
723
23
101409
543
547
07
664
630
nmnm
nmnm
nmnm
nm075
1910
-
FU3-PL
-21-
TiD3
Fatu
Kapa
Tutafi
Whitesm
oker
1626
293
294
292
1028
4541
701
51
09
1367
528
513
03
639
640
nmnm
nmnm
nmnm
nm075
1910
-
FU3-PL
-21-
TiG3
Fatu
Kapa
Tutafi
Whitesm
oker
1626
293
294
365
1027
4541
700
50
08
1371
528
510
08
633
633
nmnm
nmnm
nmnm
nm075
20
10-
8 Geofluids
Table4
Measuredgascon
centratio
nandassociated
stableiso
topicratiosh
ydrothermalflu
idsfromtheK
uloL
asiand
FatuKa
paventfieldsVa
luesoflogfH2werec
alculated
usingS
UPC
RT92
with
thes
lop9
8database
Samplen
ame
Site
H2S
N2
3He
RRa
H2
logfH2
CH4
CO2
C 2H6
C 2H4
C 3H8
C 3H6
n-C 4
H10n-C 5
H12120575D(H2)120575D(C
H4)12057513C(C
O2)12057513C(C
H4)12057513C(C2H6)12057513C(C3H8)12057513C(C4H10)
mM
mM
mM
mM
mM
mM120583M120583M120583M120583M120583M
120583M
permilpermil
permilpermil
permilpermil
permilSeaw
ater
059
nmnmltLO
D-ltLO
D23
nmnm
nmnm
nmnm
nmnm
nmnm
nmnm
nmFU
-PL-05-TiG1
KuloLasi
012
nmnmltLO
Q-
0001
26ltLO
DnmltLO
DnmltLO
DltLO
Dnm
nmnm
nmnm
nmnm
FU-PL-06-TiD
4Ku
loLasi
166
010
nmnm
114
-0001
13002
0005
000
6000
40005
0005minus323
nm
minus32
minus29
minus27
minus26
nmFU
-PL-06-TiG3
KuloLasi
505
143
nmnm
198minus311
000
651
011
004
20028
0030
0024
000
6minus306
nm
minus41
minus23
minus26
minus26
minus24
FU-PL-06-TiD
1Ku
loLasi
039
248
nmnm
618minus362
000
430
01
0017
0017
0020
0012
000
4minus300
nm
minus19
minus28
minus24
minus26
minus24
FU-PL-06-TiG1
KuloLasi
079
nmnm
104minus440
0001
10002
000
90005
0007
0005
0001minus316
nm
minus02
minus272
minus22
minus26
minus24
FU3-PL
-04-TiG3
Stephanie
091
09311119864minus08
86
003minus18
70114
155ltLO
DltLO
DltLO
DltLO
DltLO
D17
nmnm
nmnm
nmnm
nmFU
3-PL
-08-TiD1
Stephanie
123
198
nm006minus15
70235
290ltLO
DltLO
DltLO
DltLO
DltLO
D32minus676minus108
minus5
minus217
nmnm
nmFU
3-PL
-08-TiG1
Stephanie
098
24744119864minus09
76005minus16
50205
257ltLO
DltLO
DltLO
DltLO
DltLO
D29
nmnm
nmnm
nmnm
nmFU
3-PL
-09-TiD2
Stephanie
023
04819119864minus09
70004minus17
50059
60ltLO
DltLO
DltLO
DltLO
DltLO
D07minus436minus111
minus53
minus222
nmnm
nmFU
3-PL
-06-TiD1
Carla
134
05071119864minus09
96001minus235
0021
45ltLO
DltLO
DltLO
DltLO
DltLO
D05
nmnm
nmnm
nmnm
nmFU
3-PL
-08-TiD3
Carla
019
33317119864minus08
98005minus16
5006
6119ltLO
DltLO
DltLO
DltLO
DltLO
D15
minus410minus109
minus47
minus215
nmnm
nmFU
3-PL
-11-T
iG3
Idef
X113
07818119864minus08
98003minus18
70085
100ltLO
DltLO
DltLO
DltLO
DltLO
D11
nmnm
nmnm
nmnm
nmFU
3-PL
-14-TiD1
Idef
X10
012
055119864minus09
87
002minus205
0069
101ltLO
DltLO
DltLO
DltLO
DltLO
D11
minus417minus110
minus49
minus238
nmnm
nmFU
3-PL
-14-TiD2
ObelX
085
10538119864minus08
98003minus18
70110
87ltLO
DltLO
DltLO
DltLO
DltLO
D10
minus40
7minus113
minus5
minus24
nmnm
nmFU
3-PL
-14-TiD3
ObelX
054
09352119864minus09
84
002minus205
0165
92ltLO
DltLO
DltLO
DltLO
DltLO
D10
nmnm
nmnm
nmnm
nmFU
3-PL
-18-TiD1
AsterX
098
089
nmnm
001minus235
0067
92ltLO
DltLO
DltLO
DltLO
DltLO
D10
minus412minus111
minus49
minus236
nmnm
nmFU
3-PL
-17-TiG2
FatiUfu
176
08427119864minus08
99001minus259
0070
215ltLO
DltLO
DltLO
DltLO
DltLO
D23
-minus93
minus23
minus61
nmnm
nmFU
3-PL
-21-T
iD2
FatiUfu
071
20731119864minus09
99003minus211
0111
126ltLO
DltLO
DltLO
DltLO
DltLO
D15
minus410minus109
minus44
minus233
nmnm
nmFU
3-PL
-20-TiD1
Tutafi
236
11814119864minus08
92005minus18
90156
222ltLO
DltLO
DltLO
DltLO
DltLO
D24minus396minus111
minus45
minus236
nmnm
nmFU
3-PL
-21-T
iD3
Tutafi
084
167
nmnm
003minus211
0053
117ltLO
DltLO
DltLO
DltLO
DltLO
D14
minus415minus109
minus47
minus242
nmnm
nm
Geofluids 9
Table5En
dmem
bercom
positions
influ
idsfrom
theK
uloLasiandFatu
Kapa
vent
fieldsKu
loLasiendm
emberscann
otbe
extrapolated
atMg=
0Va
luespresentedhereforb
othbrinea
ndcond
ensedvapo
urph
ases
correspo
ndto
concentrations
inthefl
uidwith
thelow
estM
gElem
entalcom
positions
inendm
emberfl
uids
from
thev
arious
sites
oftheF
atuKa
pavent
field
were
calculated
usingthem
ixinglin
es(FigureS
1)andassumingMg=0Va
lues
ofthep
urestfl
uidwereu
sedwhenlin
earregressionwas
notp
ossib
le(lowast)Notethato
nlyon
esam
plew
asavailable
forthe
AsterX
site(1)
Zone
Site
Depth119879
pHNaC
lCl
SiSO
4Br
Na
KMg
CaLi
RbSr
FeMn
CuZn
NaCl
BrC
lNaK
CH4Mn
∘ C(w
t)
mM
mM
mM120583M
mM
mM
mM
mM120583M120583M120583M
120583M120583M
120583M120583M
times103
KuloLasi
NaC
lpoo
r1475
345
224
29
497
82
88
738
388
185
246
116
149
2673
4796
862
1445
078
148
210007lowast
KuloLasi
NaC
lrich
1475
345
236
43
735
146
62
1135
612
295
265
109
238
4634
9884
1416
25
175
083
154
210001lowast
Fatu
Kapa
Stephanie
1555
280
34
45
767
47lowast
00
1569
532
545
00
989
708
114282lowast
655lowast
268
66lowastltL
OD
069
205
10076lowast
Fatu
Kapa
Carla
1664
280
28
35
594
43
00
1132
477
599
00
314
691
105
114lowast
287lowast
53nm
44lowast
080
190
813
7lowast
Fatu
Kapa
Idef
X1572
270
37
39
665
42lowast
00
1282
518
664
00
443
751
113
160lowast
28lowast
60nm
34lowast
078
193
810
8lowast
Fatu
Kapa
ObelX
1669
270
46
45
771
46
00
1458
580
710
00
859
777
nmnm
nmnm
nmnm
075
189
8-
Fatu
Kapa
AsterX(1)
1540
265
44
41
693
37
101344
533
649
12511
755
nmnm
nmnm
nmnm
077
194
8-
Fatu
Kapa
FatiUfu
1523
300
38
46
790
49
00
1589
580
482
00
854
722
nmnm
nmnm
nmnm
073
201
12-
Fatu
Kapa
FatiUfu
1503
280
33
41
700
49
00
1380
538
400
00
650
583
nmnm
nmnm
nmnm
077
197
13-
Fatu
Kapa
Tutafi
1580
315
41
42
713
51
00
1405
535
529
00
651
635
nmnm
nmnm
nmnm
075
197
10-
IAPS
OStandard
sw-
--
32
546
00
282
839
468
102
532
103
2713
90ltLO
DltLO
DltLO
DltLO
D09
1546
-Ku
loLasi
References
w1150
--
32
551
01
290
833
457
98532
106
2544
93ltLO
DltLO
DltLO
DltL
OD
083
1547
-Fatu
Kapa
References
w1488
--
33
565
00
288
841
483
104
545
107
2258ltLO
DltLO
DltLO
DltLO
DltL
OD
085
1546
-Fatu
Kapa
References
w1572
2-
33
557
00
287
841
477
104
542
108
23nm
nmnm
nmnm
nm086
1546
-lowastMaxim
umvaluew
henlin
earregressionwas
notp
ossib
le(1)on
lyon
esam
ple
10 Geofluids
(a)
(b)
(c)
Figure 3 (a) and (b) Photographs of anhydrite structures observed at Stephanie Carla IdefX AsterX and ObelX site (c) Photographs of greysmokers associated with sulphides structures observed at Fati Ufu and Tutafi Copyrights from Ifremer FUTUNA 3 cruise
02468
1012141618
0 10 20 30 40 50 60Mg (mM)
Kulo Lasi
AcetateFormate
SW-acetateSW-formate
Con
cent
ratio
n(
M)
Figure 4 Mixing lines of formate and acetate versus Mg for the Kulo Lasi fluids Note that the reference deep-sea water sample (FU-PL05-TiG2 noted as SW here) was taken at 1150m depth above the southern wall of the caldera (see Figure 1 for location and Table 3) and thus verylikely within the plume [7] This would account for the unusual concentrations of formate and acetate detected
Geofluids 11
Carla Acetate was detected in all analysed samples andconcentrations were an order of magnitude higher than theones of formate (543ndash2309 ppb) (Table 6)
Heavier extractable organic compounds were notdetected in the dry control experiment and only a few weredetectable but below limit of quantification (LOQ) in theMQ water blank experiment (Table 6) This showed thatsample preparation and storage could be considered ascontamination-free steps The levels of heavier extractableorganic compounds appeared rather high in the referencewater at Fatu Kapa certainly because of the overall spreadhydrothermal discharges and diffuse venting in the region [7](Table 6 Figure 5) This sample was indeed taken mid-waybetween ObelX and AsterX fields at about 20m above theseafloor As a consequence it is difficult to assess possiblecontamination originating from sampling device or seawatercontribution in the present case However earlier studieshave shown that they generally did not represent majorsources of contamination as for the studied compounds[27 37] Nevertheless in comparison to deep-sea waterboth the qualitative (Kulo Lasi) and quantitative (FatuKapa) data obtained suggested enrichment of the fluidsin hydrothermally derived compounds namely n-alkanes(C9ndashC12) n-FAs (C9 C12 C14ndashC18) and PAHs (fluorenephenanthrene pyrene) ([39] Table 6 Figures 5 and 6)Such enrichment was unclear for gtC12 n-alkanes C10C11 C13 n-FAs BTEXs naphthalene acenaphthene andfluoranthene because of their very low concentration andorthe measurement uncertainty
Differences in concentrations seemed to exist among thevents over the Fatu Kapa area Fluids from the Stephanie ventfield had concentrations in hydrocarbons equal or below thereference water sample whereas they were clearly enrichedin C9 C12 C14ndashC18 n-FAs The Carla fluids were slightlyenriched in C9ndashC12 n-alkanes and showed the highest con-centrations in PAHs Fluids from IdefX Fati Ufu and Tutafishared some similarities a strong enrichment in decane andundecane alike concentrations in PAHs and the presence ofsignificant amounts of xylene However fluids expelled at theTutafi vent appeared the most enriched in C9ndashC11 n-alkanesand xylenes In terms of fatty acids and considering theanalytical error the 5 vents showed consistent concentrationswith C9 C16 and C18 being major Note that fluids from FatiUfu seemed depleted in C17 and C18
Generally we did not observe strong linear correlationbetween the concentration of individual compounds andMgNonetheless these relations showed that both enrichmentand depletion of organic compounds seemed to occur inhydrothermal fluids versus deep-sea water
5 Discussion
The elemental and gas composition of hydrothermal fluidsis mainly affected by waterrock interactions and thus thenature of the host rocks phase separation magmatic fluidcontribution conductive cooling and seawater mixing inlocal recharge zones [45] In the following discussion weattempt to unravel the occurrence of these various processes
both at Kulo Lasi and at Fatu Kapa Much less is known onprocesses that control organic geochemistry and are thereforediscussed here as well as some implications of the presenceof organic compounds in hydrothermal fluids Implicationsrelated to the composition of the fluids are dependent onfluxes therefore we give here an attempt to provide order ofmagnitude estimates of heat and mass fluxes
51 Plume-Fluids Relations The geochemistry and dynamicsof the plumes over the Wallis and Futuna region havebeen studied elsewhere [7] The Kulo Lasi plume has beenproposed to be the result of both high-119879 and diffuse ventingfrom multiple vents located both on the floor and on thewall of the caldera Consistently both types of venting havebeen observed [6] Helium nephelometry and Mn profilesrecorded above the northern sampling area showed constantelevated concentrations in the 300masf and were assumedto be the results of diffuse venting Our results show thatthey are obviously the result of the numerous small blacksmokers observed on the seafloor (Figure 2) The methaneconcentration in the sampled fluids was extremely low whichcannot account for the elevated concentration of CH4 inthe water column reported by Konn et al [7] The strongdifference in the CH4Mn ratios between the plume (07ndash45)and the sampled fluids (0001ndash001) is another line of evidencethat the methane plume has another origin compared tohydrothermal fluids and likely come from degassing of thelava flows as suggested by the authors Although other fluiddischarges likely remain undiscovered this is consistent witha past eruption and accumulation of the water mass in thecaldera [39]
A great diversity of the fluid compositions was expectedfrom the geological settings and the water column survey andwas indeed confirmed by the mixing lines that point to asmany endmembers as sampled areas (Figure S1) CH4TDMratios also differed among the vents but it was not due to soleCH4 concentration variations as suggested earlier (Table 5)[7] Finally the very weak nephelometry of the Fatu Kapaplume is likely best explained by the low metal contents ofthe fluids
52 Reaction Zone Depth The solubility of Quartz in hydro-thermal fluids has been studied by different authors (eg[46]) According to these works silica concentration in thefluid may be used to estimate the depth of the reaction zoneThe silica concentration measured in the Kulo Lasi and FatuKapa fluids indicates a hydrothermal reaction zone at seaflooror in thewater column (Figure S2) Both observations suggestthat in this area fluids are not in equilibria with Quartz atthe pressure and temperature of the fluid emission And thisprevents using Si as a geothermometer to determine the depthof the reaction zone
All fluids at Fatu Kapa were indeed highly depleted inSi with respect to the Quartz saturation curve at 170 bar300∘C (Si sim12mM in Figure S2) A higher temperature inthe reaction zone (gt350∘C at 200 bar) may explain a lower Siconcentration in the fluid at equilibrium as Quartz solubilitydecreases (Figure S2) The dispersion of a great number of
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Table 1 Main GC analytical parameters used for calibration and analyses of hydrothermal fluid samples Each group of compounds (n-alkanes BTEXs PAHs and n-fatty acids) was analysed using separate twisters
n-Alkanes BTEX amp PAHs n-Fatty acidsOvenInitial 119879 (∘C) 40 40 40Initial 119905 (min) 1 1 1ramp 40 to 320∘C at 12∘Cmin 40 to 320∘C at 12∘Cmin 40 to 320∘C at 20∘CminFinal 119879 (∘C) 320 320 320Final 119905 (min) 2 2 2Injector119879 (∘C) 250 250 325
Table 2 Experimental conditions used for calibration curves Linear regressions were performed on one order of magnitude concentrationdomain depending on the concentration range of the samples
syringe was transferred into a precombusted glass bottle andsix 90mL aliquots of the sample were poured into 100mLprecombusted glass vials 10mL ofMeOHwas added to avoidadsorption of the compounds onto the wall of the vialsInternal standards were added to the solutions in 2012 so thatquantification could only be achieved in Fatu Kapa fluidsExtraction was performed in sealed vials with ultrainertseptum crimps at 300 rpm and using 48 120583L PDMS Twisters(Gerstel GmbH) We focused on a selection of chemicalgroups that had previously been described as hydrothermallyderived [27] To that respect pairs of aliquots were dedicatedto analysis of n-alkanes n-FAs and both BTEXs and PAHsrespectively Extraction kinetics experiments showed thatchemical equilibrium was reached after 5 h of extraction forn-alkanes 4 h for PAHs and 14 h for n-FAs (Konn unpub-lished results) Twisters were then removed rinsed with MQwater dried and stored at +4∘C until analyses by ThermalDesorption-Gas Chromatography-Mass Spectrometry (TD-GC-MS) [37] Analytical parameters were adjusted for eachgroup of compounds (Table 1)
For each batch of conditioned Twisters one was sparedstored at +4∘C and analysed in the same run as the otherTwistersThis dry blank aimed at showing any contaminationthat could have occurred during conditioning storage andtransport MQ water samples were prepared and extractedon board as regular hydrothermal samples to check if anycontaminations could have occurred during the samplepreparation step Deep-sea water was also collected pro-cessed and analysed using the same titanium syringes andaccording to the same protocols as for hydrothermal fluidsamples and thus constitute the reference blank experiment
Calibration was achieved using a commercial stan-dard solution of BTEXs and 3 custom standard solu-tions of C9ndashC20 n-alkanes C6ndashC18 n-FAs and PAHs con-taining naphthalene (N) Acenaphtene (A) Fluorene (F)Phenanthrene (Ph) Anthracene (An) Fluoranthene (Fl)and pyrene (Py) (LGC Standards LGC Ltd) Deuteratedn-alkanes (C10D22 and C14D34) methyl esters (C9H18O2
and C15H30O2) and deuterated PAHs (naphthalene-D8Biphenyl-D8 and Phenanthrene-D10) were used as inter-nal standards (IS) Calibration curves (Concentration (ana-lyte)Concentration (IS) versus Area (analyte)Area (IS))were obtained using at least five concentration levels thatwere replicated 3 times (Table 2) Although the correlationcoefficient of the linear regressions was satisfactory for allcompounds the significance and lack of fit of the modelwere checked by statistical tests before validation A series ofStudent Barlett Chi-square and Fisher tests was run for eachindividual compound using the Lumiere software The bestfitting model was then chosen for each case and confidenceintervals were calculated
4 Results
Altogether 35 hot fluid samples were collected in the studyarea from 8 different sites Kulo Lasi caldera (6) on theone hand and Stephanie (7) Carla (4) IdefX (4) ObelX (3)AsterX (1) Fati Ufu (6) and Tutafi (4) on the other handall located in the Fatu Kapa area (Figure 1) The KuloLasi smokers occurred at sim1500m depth on recent lavaflows and consisted in a multitude of short (sim25 cm) andnarrow (sim3ndash5 cm) diameter anhydrite chimneys containing asmall percentage of sphalerite (ZnS) chalcopyrite (CuFeS2)isocubanite (CuFe2S3) pyrrhotite (Fe1minus119909S) and pyrite (FeS2)(Figure 2)The temperature was consistently about 343∘C andthe pH approached 22ndash23 (Table 3) In the FatuKapa area wecould distinguish two types of hydrothermal environments at1550ndash1650m depth Translucent 270ndash290∘C fluids associatedwith anhydrite chimneys (up to 25m tall and 25m indiameter) characterised Stephanie Carla IdefX ObelX andAsterX sites while gt300∘C milky to grey fluids associatedwith sulphide chimneys were characteristic of the southwestregion including Fati Ufu and Tutafi sites (Figure 3 Table 3)
41 Gas Concentrations of gases in all fluids as well as stableisotopes data are compiled in Table 4 Samples recovered
Geofluids 5
Figure 2 Photographs of sulphide chimneys and young lava flowsobserved on the floor of the Kulo Lasi caldera Copyrights fromIfremer FUTUNA 1 cruise
from Kulo Lasi were extremely poor in CH4 (lt001mM) butcontained the series of C2ndashC5 hydrocarbons Samples fromFatuKapa had higher concentration of CH4 (005ndash0235mM)but only n-pentane (05ndash32 120583M) could be detected andquantified in terms of longer hydrocarbons One samplefrom Kulo Lasi was found to be extremely rich in H2 withnearly 20mM while the others ranged from 1 to 6mM andwere below 005mM at Fatu Kapa H2S was highly variablebetween the 3 sampled chimneys at Kulo Lasi (039 166 and505mM) while it was found rather homogeneous at FatuKapa with values around 1mM CO2 concentrations weremore elevated at Fatu Kapa (45ndash29mM) compared to KuloLasi (1ndash5mM)
Helium isotope ratios were in the range 70ndash99 Ra overthe Fatu Kapa area in agreement with plume data [7] Theycould not be measured at Kulo Lasi unfortunately Carbonisotopes ratios were around minus5permil for CO2 at Fatu Kapawhereas at Kulo Lasi the ratio showed very different results
ranging from minus02 to minus41permil As for methane 12057513C wereslightly lower at Kulo Lasi (simminus28permil) versus Fatu Kapa (simminus23permil) and 120575D was about minus110permil in all samples from FatuKapa 120575D (CH4) could not bemeasured in theKulo Lasi fluidsbecause of the too low concentrations of CH4 Carbon isotoperatios of longer hydrocarbons were in the minus27 to minus22permil atboth vent fields To be noted one sample from Fati Ufu in theFatu Kapa area showed remarkably lower isotopic ratios with12057513C (CO2) = minus23permil 12057513C (CH4) = minus61permil and 120575D (CH4) =minus93permil We do not have any explanation for this but do nothave any reasons either to consider it as an outlier
42 Major and Minor Elements Major and minor elementsmeasurements data are compiled in Table 3 Fluids fromFatu Kapa all exhibited a higher salinity than seawater up to46 wt NaCl whereas at Kulo Lasi fluids with both lower(28 wt NaCl) and higher (43 wt NaCl) salinity weresampled Mg and SO4 concentrations tend to be zero in thepurest samples at Fatu Kapa But the purest fluids from KuloLasi showed significant levels of Mg and SO4 associated withan extremely acidic pH (lt25) and a high119879 (343∘C) Althoughwe cannot totally discard that some mixing with seawateroccurred endmember concentrations of the Kulo Lasi fluidswere then estimated to be close to the purest fluids sampledwhereas they were obtained from mixing lines at Fatu Kapaassuming Mg zero (Table 5)
Fluids from Fatu Kapa were enriched compared to sea-water in alkali alkaline Earth and transition metals as wellas in strontium bromide and silica Conversely the fluidsfrom Kulo Lasi exhibited a much more complex patternThey were all highly enriched in transition metals and silicacompared to seawater and fluids from Fatu Kapa (eg Fe upto sim10mM) The enrichment versus seawater in alkali metalswas not as striking as for Fatu Kapa fluids As for the alkalineEarth metals the amount of Ca was identical to seawater andfluids were depleted in Sr compared to seawater Finally bothdepletion and enrichment in Br were observed in the fluidsfrom Kulo Lasi
43 Organic Geochemistry First of all we would like to men-tion that because solubility of organic compounds decreaseswith119879 and because samples were processed at room tempera-ture the measured concentrations are probably lower than insitu concentrations Moreover it is very likely that a portionof theOMwas adsorbed on small particles in the fluids whichare not taken into account using our extraction and analyticaltechniques As a result the concentrations we report hereprobably represent lower estimates of in situ concentrationsHowever since in situ measurement techniques are notavailable yet these values are the best estimates we can obtainNote that they also are the first to be published for SVOCs
Formate and acetate reached 163 and 155 120583M respec-tively and covaried withMg in the Kulo Lasi fluids (Figure 4)Concentrations of formate and acetate were significantlyhigher in the Fatu Kapa area but no correlation with Mgcould be observed Nevertheless the purest fluids usuallyshowed the highest concentrations Formate reached 68 ppbat Stephanie and 722 ppb at Fati Ufu whereas it could notbe detected at IdefX and Tutafi and was not measured at
6 GeofluidsTa
ble3Measuredconcentrationof
major
andminor
elem
entsin
hydrotherm
alflu
idsfrom
theKu
loLasiandFatu
Kapa
vent
fieldsFU
X-PL
YY-TiD
ZandFU
X-PL
YY-TiGZarereplicate
samplestakenin
thesam
eorifi
ceone
aftertheo
therbut
using2
individu
alTi
syrin
ges119879m
ax(chimney)isthem
axim
um119879o
fthe
discharged
fluidforthe
givenchim
neyw
hich
wasrecorded
bythe119879
prob
eofthe
subm
arineb
efores
ampling119879m
ax(sam
ple)isthem
axim
um119879o
fthe
fluid
enterin
gthes
ampler
recorded
durin
gsamplingby
thea
uton
omou
ssensorthatw
ascoup
led
atthen
ozzle
ofthes
ampler
Sample
name
Zone
Site
Descriptio
nDepth119879max
(sam
ple)
∘C
119879max
(chimney)
∘C
pHd20
Kgmminus3
S permilNaC
l(w
t)
Cl mM
Si mM
SO4
mM
Br 120583MNa
mM
K mM
Mg
mM
Ca mM
Li 120583MLi 120583M
Rb 120583MSr 120583M
Fe 120583MMn120583M
Cu 120583MZn 120583M
NaCl
BrC
ltimes103
NaK
CH4M
n
IAPS
O-
-Standard
water
--
--
-35
32
546
00
282
839
468
102
532
103
2727
1390ltLO
DltLO
DltLO
DltLO
D09
1546
-FU
-PL-05-
TiG2
KuloLasi
South(out)
Referencew
ater
1150
--
-10
2335
32
551
01
290
833
457
98532
106
2528
44
93ltLO
DltLO
DltLO
DltLO
D083
1547
-
FU-PL-05-
TiG1
KuloLasi
South(in
)Diffusefl
uidabove
worms
1414
328
-596
1023
3532
549
02
293
833
457
99532
106
2852
46
92ltLO
DltLO
D14
15083
1546
-
FU-PL-06-
TiG4
KuloLasi
North
(in)
Beehivetypeb
lack
smoker
1475
1341
332
607
1022
3330
516
10270
822
448
106
498
105
3354
53
84123
3217
31
087
1642
-
FU-PL-06-
TiD4
KuloLasi
North
(in)
Beehivetypeb
lack
smoker
1475
136
332
558
1021
3128
485
21
239
994
406
95457
102
3255
61
7478
7613
15084
20
430010
FU-PL-06-
TiG3
KuloLasi
North
(in)
Translu
cent
smoker
1475
3423
3307
224
1017
3229
497
82
88
738
388
185
246
116
149
156
2673
4796
862
1445
078
1521
0007
FU-PL-06-
TiD3
KuloLasi
North
(in)
Translu
cent
smoker
1475
3377
3307
237
1018
3330
517
84
107
770
405
166
286
108
115149
2494
4283
788
42
41078
1524
-
FU-PL-06-
TiD1
KuloLasi
North
(in)
Blacksm
oker
1475
3432
3451
236
102
4743
735
146
62
1135
612
295
265
109
238
249
4634
9884
1416
25
175
083
1521
-
FU-PL-06-
TiG1
KuloLasi
North
(in)
Blacksm
oker
1475
3432
3451
332
1028
4440
689
108
120
1051
565
237
349
108
176
197
3691
6845
1064
2077
082
1524
0001
FU3-PL
-03-
TiD3
Fatu
Kapa
20masf
Referencew
ater
1488
--
--
-33
565
00
288
841
483
104
545
107
2251
6ltLO
DltLO
DltLO
DltLO
DltLO
D085
1546
-
FU3-PL
-14-
TiG2
Fatu
Kapa
23masf
Referencew
ater
1572
2-
--
3633
557
00
287
841
477
104
542
108
23nm
nmnm
nmnm
nmnm
086
1546
-
FU3-PL
-04-
TiD3
Fatu
Kapa
Stephanie
Translu
cent
smoker
1554
213
279
465
103
4541
704
07
109
1300
519
398
187
696
472
568
80ltLO
D169
166
nmltLO
D074
1813
-
FU3-PL
-04-
TiG3
Fatu
Kapa
Stephanie
Translu
cent
smoker
1554
213
279
464
103
4440
686
10129
1240
513
365
225
628
420
504
71169
nm141
82ltLO
D075
1814
0805
FU3-PL
-08-
TiD1
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
289
280
410
3149
45
770
38
131574
535
542
08
989
705
804
121
268
655
265
66ltLO
D069
20
100886
FU3-PL
-08-
TiG1
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
289
280
341
1031
4945
772
47
07
1592
537
547
05
987
708
807
122
283
167
269
nmltLO
D070
21
100762
FU3-PL
-08-
TiD2
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
291
280
383
1031
4844
748
43
05
1537
520
529
06
953
684
806
116ltLO
D148
259
nmltLO
D070
21
10-
FU3-PL
-09-
TiD2
Fatu
Kapa
Stephanie
Beehivetypeb
lack
smoker
+bacterial
mat
1650
197
236
519
1026
4037
629
17198
1052
500
244
374
378
230
293
36149
nm65
nm10
079
1721
0902
FU3-PL
-09-
TiG2
Fatu
Kapa
Stephanie
Beehivetypeb
lack
smoker
+bacterial
mat
1559
197
236
542
1025
3835
600
10238
959
489
185
443
264
143
193
23ltLO
Dnm
23nmltLO
D081
1626
-
FU3-PL
-06-
TiD1
Fatu
Kapa
Carla
Translu
cent
smoker
1663
278
270
503
1024
3734
576
17185
927
482
285
352
179
260
310
42101
nmnm
nmltLO
D084
1617
-
FU3-PL
-06-
TiG1
Fatu
Kapa
Carla
Translu
cent
smoker
1663
278
270
491
1024
3734
579
07
127
984
476
378
236
222
391
455
63ltLO
D18
32nmltLO
D082
1713
-
FU3-PL
-08-
TiD3
Fatu
Kapa
Carla
Translu
cent
smoker
1664
281
281
278
1024
3835
594
45
11113
9479
596
04
315
690
746
104
115nm
48nm
44
080
198
1365
FU3-PL
-08-
TiG3
Fatu
Kapa
Carla
Translu
cent
smoker
1664
281
281
417
1024
3835
592
40
19112
0477
577
27
303
655
720
96ltLO
D288
39nmltLO
D081
198
-
FU3-PL
-11-
TiD3
Fatu
Kapa
IdefX
Translu
cent
smoker
1573
259
258
49
1025
4137
637
1483
1142
509
498
155
350
541
612
78ltLO
D38
26nmltLO
D080
1810
-
FU3-PL
-11-
TiG3
Fatu
Kapa
IdefX
Translu
cent
smoker
1573
259
258
443
1025
4339
664
41
191268
518
635
20
447
733
802
110160
nm46
nm25
078
198
1848
Geofluids 7
Table3Con
tinued
Sample
name
Zone
Site
Descriptio
nDepth119879max
(sam
ple)
∘C
119879max
(chimney)
∘C
pHd20
Kgmminus3
S permilNaC
l(w
t)
Cl mM
Si mM
SO4
mM
Br 120583MNa
mM
K mM
Mg
mM
Ca mM
Li 120583MLi 120583M
Rb 120583MSr 120583M
Fe 120583MMn120583M
Cu 120583MZn 120583M
NaCl
BrC
ltimes103
NaK
CH4M
n
FU3-PL
-14-
TiD1
Fatu
Kapa
IdefX
Translu
cent
smoker
1572
271
271
373
1025
4339
665
42
111282
519
662
08
434
764
823
120
144
2864
nm34
078
198
1078
FU3-PL
-14-
TiG1
Fatu
Kapa
IdefX
Translu
cent
smoker
1572
271
271
397
1025
4239
661
41
08
1279
515
657
08
429
757
825
119ltLO
Dnm
62nmltLO
D078
198
-
FU3-PL
-14-
TiD2
Fatu
Kapa
ObelX
Translu
cent
smoker
1669
272
-459
103
4945
769
45
07
1506
577
694
13655
757
nmnm
nmnm
nmnm
nm075
20
8-
FU3-PL
-14-
TiD3
Fatu
Kapa
ObelX
Translu
cent
smoker
1636
287
-428
103
4743
729
37
150
1283
557
588
111
650
621
nmnm
nmnm
nmnm
nm076
189
-
FU3-PL
-14-
TiG3
Fatu
Kapa
ObelX
Translu
cent
smoker
1636
287
-537
1028
4339
672
25
270
1103
528
425
253
546
415
nmnm
nmnm
nmnm
nm079
1612
-
FU3-PL
-18-
TiD1
Fatu
Kapa
AsterX
Translu
cent
smoker
1540
265
260
435
1027
4441
693
37
101344
533
649
12511
755
nmnm
nmnm
nmnm
nm077
198
-
FU3-PL
-17-
TiD2
Fatu
Kapa
FatiUfu
Greysm
oker
1522
299
303
426
1031
4743
739
33
931378
555
384
176
666
543
nmnm
nmnm
nmnm
nm075
1914
-
FU3-PL
-17-
TiG2
Fatu
Kapa
FatiUfu
Greysm
oker
1522
299
303
422
1031
4844
748
35
87
1402
562
398
159
697
569
nmnm
nmnm
nmnm
nm075
1914
-
FU3-PL
-21-
TiD1
Fatu
Kapa
FatiUfu
Greysm
oker
1523
302
301
381
1032
5046
784
47
141554
577
473
14862
717
nmnm
nmnm
nmnm
nm074
20
12-
FU3-PL
-21-
TiG1
Fatu
Kapa
FatiUfu
Greysm
oker
1523
302
301
469
103
4541
708
27
105
1292
544
347
193
603
474
nmnm
nmnm
nmnm
nm077
1816
-
FU3-PL
-21-
TiD2
Fatu
Kapa
FatiUfu
Whitesm
oker
1503
-284
327
1028
4441
694
49
04
1359
534
393
10633
573
nmnm
nmnm
nmnm
nm077
20
14-
FU3-PL
-21-
TiG2
Fatu
Kapa
FatiUfu
Whitesm
oker
1503
-284
422
1026
4239
661
39
701217
520
320
133
506
435
nmnm
nmnm
nmnm
nm079
1816
-
FU3-PL
-20-
TiD1
Fatu
Kapa
Tutafi
Greysm
oker
1580
316
317
41
1029
4642
720
26
06
1409
543
546
09
654
628
nmnm
nmnm
nmnm
nm075
20
10-
FU3-PL
-20-
TiG1
Fatu
Kapa
Tutafi
Greysm
oker
1580
316
317
414
1029
4642
723
23
101409
543
547
07
664
630
nmnm
nmnm
nmnm
nm075
1910
-
FU3-PL
-21-
TiD3
Fatu
Kapa
Tutafi
Whitesm
oker
1626
293
294
292
1028
4541
701
51
09
1367
528
513
03
639
640
nmnm
nmnm
nmnm
nm075
1910
-
FU3-PL
-21-
TiG3
Fatu
Kapa
Tutafi
Whitesm
oker
1626
293
294
365
1027
4541
700
50
08
1371
528
510
08
633
633
nmnm
nmnm
nmnm
nm075
20
10-
8 Geofluids
Table4
Measuredgascon
centratio
nandassociated
stableiso
topicratiosh
ydrothermalflu
idsfromtheK
uloL
asiand
FatuKa
paventfieldsVa
luesoflogfH2werec
alculated
usingS
UPC
RT92
with
thes
lop9
8database
Samplen
ame
Site
H2S
N2
3He
RRa
H2
logfH2
CH4
CO2
C 2H6
C 2H4
C 3H8
C 3H6
n-C 4
H10n-C 5
H12120575D(H2)120575D(C
H4)12057513C(C
O2)12057513C(C
H4)12057513C(C2H6)12057513C(C3H8)12057513C(C4H10)
mM
mM
mM
mM
mM
mM120583M120583M120583M120583M120583M
120583M
permilpermil
permilpermil
permilpermil
permilSeaw
ater
059
nmnmltLO
D-ltLO
D23
nmnm
nmnm
nmnm
nmnm
nmnm
nmnm
nmFU
-PL-05-TiG1
KuloLasi
012
nmnmltLO
Q-
0001
26ltLO
DnmltLO
DnmltLO
DltLO
Dnm
nmnm
nmnm
nmnm
FU-PL-06-TiD
4Ku
loLasi
166
010
nmnm
114
-0001
13002
0005
000
6000
40005
0005minus323
nm
minus32
minus29
minus27
minus26
nmFU
-PL-06-TiG3
KuloLasi
505
143
nmnm
198minus311
000
651
011
004
20028
0030
0024
000
6minus306
nm
minus41
minus23
minus26
minus26
minus24
FU-PL-06-TiD
1Ku
loLasi
039
248
nmnm
618minus362
000
430
01
0017
0017
0020
0012
000
4minus300
nm
minus19
minus28
minus24
minus26
minus24
FU-PL-06-TiG1
KuloLasi
079
nmnm
104minus440
0001
10002
000
90005
0007
0005
0001minus316
nm
minus02
minus272
minus22
minus26
minus24
FU3-PL
-04-TiG3
Stephanie
091
09311119864minus08
86
003minus18
70114
155ltLO
DltLO
DltLO
DltLO
DltLO
D17
nmnm
nmnm
nmnm
nmFU
3-PL
-08-TiD1
Stephanie
123
198
nm006minus15
70235
290ltLO
DltLO
DltLO
DltLO
DltLO
D32minus676minus108
minus5
minus217
nmnm
nmFU
3-PL
-08-TiG1
Stephanie
098
24744119864minus09
76005minus16
50205
257ltLO
DltLO
DltLO
DltLO
DltLO
D29
nmnm
nmnm
nmnm
nmFU
3-PL
-09-TiD2
Stephanie
023
04819119864minus09
70004minus17
50059
60ltLO
DltLO
DltLO
DltLO
DltLO
D07minus436minus111
minus53
minus222
nmnm
nmFU
3-PL
-06-TiD1
Carla
134
05071119864minus09
96001minus235
0021
45ltLO
DltLO
DltLO
DltLO
DltLO
D05
nmnm
nmnm
nmnm
nmFU
3-PL
-08-TiD3
Carla
019
33317119864minus08
98005minus16
5006
6119ltLO
DltLO
DltLO
DltLO
DltLO
D15
minus410minus109
minus47
minus215
nmnm
nmFU
3-PL
-11-T
iG3
Idef
X113
07818119864minus08
98003minus18
70085
100ltLO
DltLO
DltLO
DltLO
DltLO
D11
nmnm
nmnm
nmnm
nmFU
3-PL
-14-TiD1
Idef
X10
012
055119864minus09
87
002minus205
0069
101ltLO
DltLO
DltLO
DltLO
DltLO
D11
minus417minus110
minus49
minus238
nmnm
nmFU
3-PL
-14-TiD2
ObelX
085
10538119864minus08
98003minus18
70110
87ltLO
DltLO
DltLO
DltLO
DltLO
D10
minus40
7minus113
minus5
minus24
nmnm
nmFU
3-PL
-14-TiD3
ObelX
054
09352119864minus09
84
002minus205
0165
92ltLO
DltLO
DltLO
DltLO
DltLO
D10
nmnm
nmnm
nmnm
nmFU
3-PL
-18-TiD1
AsterX
098
089
nmnm
001minus235
0067
92ltLO
DltLO
DltLO
DltLO
DltLO
D10
minus412minus111
minus49
minus236
nmnm
nmFU
3-PL
-17-TiG2
FatiUfu
176
08427119864minus08
99001minus259
0070
215ltLO
DltLO
DltLO
DltLO
DltLO
D23
-minus93
minus23
minus61
nmnm
nmFU
3-PL
-21-T
iD2
FatiUfu
071
20731119864minus09
99003minus211
0111
126ltLO
DltLO
DltLO
DltLO
DltLO
D15
minus410minus109
minus44
minus233
nmnm
nmFU
3-PL
-20-TiD1
Tutafi
236
11814119864minus08
92005minus18
90156
222ltLO
DltLO
DltLO
DltLO
DltLO
D24minus396minus111
minus45
minus236
nmnm
nmFU
3-PL
-21-T
iD3
Tutafi
084
167
nmnm
003minus211
0053
117ltLO
DltLO
DltLO
DltLO
DltLO
D14
minus415minus109
minus47
minus242
nmnm
nm
Geofluids 9
Table5En
dmem
bercom
positions
influ
idsfrom
theK
uloLasiandFatu
Kapa
vent
fieldsKu
loLasiendm
emberscann
otbe
extrapolated
atMg=
0Va
luespresentedhereforb
othbrinea
ndcond
ensedvapo
urph
ases
correspo
ndto
concentrations
inthefl
uidwith
thelow
estM
gElem
entalcom
positions
inendm
emberfl
uids
from
thev
arious
sites
oftheF
atuKa
pavent
field
were
calculated
usingthem
ixinglin
es(FigureS
1)andassumingMg=0Va
lues
ofthep
urestfl
uidwereu
sedwhenlin
earregressionwas
notp
ossib
le(lowast)Notethato
nlyon
esam
plew
asavailable
forthe
AsterX
site(1)
Zone
Site
Depth119879
pHNaC
lCl
SiSO
4Br
Na
KMg
CaLi
RbSr
FeMn
CuZn
NaCl
BrC
lNaK
CH4Mn
∘ C(w
t)
mM
mM
mM120583M
mM
mM
mM
mM120583M120583M120583M
120583M120583M
120583M120583M
times103
KuloLasi
NaC
lpoo
r1475
345
224
29
497
82
88
738
388
185
246
116
149
2673
4796
862
1445
078
148
210007lowast
KuloLasi
NaC
lrich
1475
345
236
43
735
146
62
1135
612
295
265
109
238
4634
9884
1416
25
175
083
154
210001lowast
Fatu
Kapa
Stephanie
1555
280
34
45
767
47lowast
00
1569
532
545
00
989
708
114282lowast
655lowast
268
66lowastltL
OD
069
205
10076lowast
Fatu
Kapa
Carla
1664
280
28
35
594
43
00
1132
477
599
00
314
691
105
114lowast
287lowast
53nm
44lowast
080
190
813
7lowast
Fatu
Kapa
Idef
X1572
270
37
39
665
42lowast
00
1282
518
664
00
443
751
113
160lowast
28lowast
60nm
34lowast
078
193
810
8lowast
Fatu
Kapa
ObelX
1669
270
46
45
771
46
00
1458
580
710
00
859
777
nmnm
nmnm
nmnm
075
189
8-
Fatu
Kapa
AsterX(1)
1540
265
44
41
693
37
101344
533
649
12511
755
nmnm
nmnm
nmnm
077
194
8-
Fatu
Kapa
FatiUfu
1523
300
38
46
790
49
00
1589
580
482
00
854
722
nmnm
nmnm
nmnm
073
201
12-
Fatu
Kapa
FatiUfu
1503
280
33
41
700
49
00
1380
538
400
00
650
583
nmnm
nmnm
nmnm
077
197
13-
Fatu
Kapa
Tutafi
1580
315
41
42
713
51
00
1405
535
529
00
651
635
nmnm
nmnm
nmnm
075
197
10-
IAPS
OStandard
sw-
--
32
546
00
282
839
468
102
532
103
2713
90ltLO
DltLO
DltLO
DltLO
D09
1546
-Ku
loLasi
References
w1150
--
32
551
01
290
833
457
98532
106
2544
93ltLO
DltLO
DltLO
DltL
OD
083
1547
-Fatu
Kapa
References
w1488
--
33
565
00
288
841
483
104
545
107
2258ltLO
DltLO
DltLO
DltLO
DltL
OD
085
1546
-Fatu
Kapa
References
w1572
2-
33
557
00
287
841
477
104
542
108
23nm
nmnm
nmnm
nm086
1546
-lowastMaxim
umvaluew
henlin
earregressionwas
notp
ossib
le(1)on
lyon
esam
ple
10 Geofluids
(a)
(b)
(c)
Figure 3 (a) and (b) Photographs of anhydrite structures observed at Stephanie Carla IdefX AsterX and ObelX site (c) Photographs of greysmokers associated with sulphides structures observed at Fati Ufu and Tutafi Copyrights from Ifremer FUTUNA 3 cruise
02468
1012141618
0 10 20 30 40 50 60Mg (mM)
Kulo Lasi
AcetateFormate
SW-acetateSW-formate
Con
cent
ratio
n(
M)
Figure 4 Mixing lines of formate and acetate versus Mg for the Kulo Lasi fluids Note that the reference deep-sea water sample (FU-PL05-TiG2 noted as SW here) was taken at 1150m depth above the southern wall of the caldera (see Figure 1 for location and Table 3) and thus verylikely within the plume [7] This would account for the unusual concentrations of formate and acetate detected
Geofluids 11
Carla Acetate was detected in all analysed samples andconcentrations were an order of magnitude higher than theones of formate (543ndash2309 ppb) (Table 6)
Heavier extractable organic compounds were notdetected in the dry control experiment and only a few weredetectable but below limit of quantification (LOQ) in theMQ water blank experiment (Table 6) This showed thatsample preparation and storage could be considered ascontamination-free steps The levels of heavier extractableorganic compounds appeared rather high in the referencewater at Fatu Kapa certainly because of the overall spreadhydrothermal discharges and diffuse venting in the region [7](Table 6 Figure 5) This sample was indeed taken mid-waybetween ObelX and AsterX fields at about 20m above theseafloor As a consequence it is difficult to assess possiblecontamination originating from sampling device or seawatercontribution in the present case However earlier studieshave shown that they generally did not represent majorsources of contamination as for the studied compounds[27 37] Nevertheless in comparison to deep-sea waterboth the qualitative (Kulo Lasi) and quantitative (FatuKapa) data obtained suggested enrichment of the fluidsin hydrothermally derived compounds namely n-alkanes(C9ndashC12) n-FAs (C9 C12 C14ndashC18) and PAHs (fluorenephenanthrene pyrene) ([39] Table 6 Figures 5 and 6)Such enrichment was unclear for gtC12 n-alkanes C10C11 C13 n-FAs BTEXs naphthalene acenaphthene andfluoranthene because of their very low concentration andorthe measurement uncertainty
Differences in concentrations seemed to exist among thevents over the Fatu Kapa area Fluids from the Stephanie ventfield had concentrations in hydrocarbons equal or below thereference water sample whereas they were clearly enrichedin C9 C12 C14ndashC18 n-FAs The Carla fluids were slightlyenriched in C9ndashC12 n-alkanes and showed the highest con-centrations in PAHs Fluids from IdefX Fati Ufu and Tutafishared some similarities a strong enrichment in decane andundecane alike concentrations in PAHs and the presence ofsignificant amounts of xylene However fluids expelled at theTutafi vent appeared the most enriched in C9ndashC11 n-alkanesand xylenes In terms of fatty acids and considering theanalytical error the 5 vents showed consistent concentrationswith C9 C16 and C18 being major Note that fluids from FatiUfu seemed depleted in C17 and C18
Generally we did not observe strong linear correlationbetween the concentration of individual compounds andMgNonetheless these relations showed that both enrichmentand depletion of organic compounds seemed to occur inhydrothermal fluids versus deep-sea water
5 Discussion
The elemental and gas composition of hydrothermal fluidsis mainly affected by waterrock interactions and thus thenature of the host rocks phase separation magmatic fluidcontribution conductive cooling and seawater mixing inlocal recharge zones [45] In the following discussion weattempt to unravel the occurrence of these various processes
both at Kulo Lasi and at Fatu Kapa Much less is known onprocesses that control organic geochemistry and are thereforediscussed here as well as some implications of the presenceof organic compounds in hydrothermal fluids Implicationsrelated to the composition of the fluids are dependent onfluxes therefore we give here an attempt to provide order ofmagnitude estimates of heat and mass fluxes
51 Plume-Fluids Relations The geochemistry and dynamicsof the plumes over the Wallis and Futuna region havebeen studied elsewhere [7] The Kulo Lasi plume has beenproposed to be the result of both high-119879 and diffuse ventingfrom multiple vents located both on the floor and on thewall of the caldera Consistently both types of venting havebeen observed [6] Helium nephelometry and Mn profilesrecorded above the northern sampling area showed constantelevated concentrations in the 300masf and were assumedto be the results of diffuse venting Our results show thatthey are obviously the result of the numerous small blacksmokers observed on the seafloor (Figure 2) The methaneconcentration in the sampled fluids was extremely low whichcannot account for the elevated concentration of CH4 inthe water column reported by Konn et al [7] The strongdifference in the CH4Mn ratios between the plume (07ndash45)and the sampled fluids (0001ndash001) is another line of evidencethat the methane plume has another origin compared tohydrothermal fluids and likely come from degassing of thelava flows as suggested by the authors Although other fluiddischarges likely remain undiscovered this is consistent witha past eruption and accumulation of the water mass in thecaldera [39]
A great diversity of the fluid compositions was expectedfrom the geological settings and the water column survey andwas indeed confirmed by the mixing lines that point to asmany endmembers as sampled areas (Figure S1) CH4TDMratios also differed among the vents but it was not due to soleCH4 concentration variations as suggested earlier (Table 5)[7] Finally the very weak nephelometry of the Fatu Kapaplume is likely best explained by the low metal contents ofthe fluids
52 Reaction Zone Depth The solubility of Quartz in hydro-thermal fluids has been studied by different authors (eg[46]) According to these works silica concentration in thefluid may be used to estimate the depth of the reaction zoneThe silica concentration measured in the Kulo Lasi and FatuKapa fluids indicates a hydrothermal reaction zone at seaflooror in thewater column (Figure S2) Both observations suggestthat in this area fluids are not in equilibria with Quartz atthe pressure and temperature of the fluid emission And thisprevents using Si as a geothermometer to determine the depthof the reaction zone
All fluids at Fatu Kapa were indeed highly depleted inSi with respect to the Quartz saturation curve at 170 bar300∘C (Si sim12mM in Figure S2) A higher temperature inthe reaction zone (gt350∘C at 200 bar) may explain a lower Siconcentration in the fluid at equilibrium as Quartz solubilitydecreases (Figure S2) The dispersion of a great number of
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Figure 2 Photographs of sulphide chimneys and young lava flowsobserved on the floor of the Kulo Lasi caldera Copyrights fromIfremer FUTUNA 1 cruise
from Kulo Lasi were extremely poor in CH4 (lt001mM) butcontained the series of C2ndashC5 hydrocarbons Samples fromFatuKapa had higher concentration of CH4 (005ndash0235mM)but only n-pentane (05ndash32 120583M) could be detected andquantified in terms of longer hydrocarbons One samplefrom Kulo Lasi was found to be extremely rich in H2 withnearly 20mM while the others ranged from 1 to 6mM andwere below 005mM at Fatu Kapa H2S was highly variablebetween the 3 sampled chimneys at Kulo Lasi (039 166 and505mM) while it was found rather homogeneous at FatuKapa with values around 1mM CO2 concentrations weremore elevated at Fatu Kapa (45ndash29mM) compared to KuloLasi (1ndash5mM)
Helium isotope ratios were in the range 70ndash99 Ra overthe Fatu Kapa area in agreement with plume data [7] Theycould not be measured at Kulo Lasi unfortunately Carbonisotopes ratios were around minus5permil for CO2 at Fatu Kapawhereas at Kulo Lasi the ratio showed very different results
ranging from minus02 to minus41permil As for methane 12057513C wereslightly lower at Kulo Lasi (simminus28permil) versus Fatu Kapa (simminus23permil) and 120575D was about minus110permil in all samples from FatuKapa 120575D (CH4) could not bemeasured in theKulo Lasi fluidsbecause of the too low concentrations of CH4 Carbon isotoperatios of longer hydrocarbons were in the minus27 to minus22permil atboth vent fields To be noted one sample from Fati Ufu in theFatu Kapa area showed remarkably lower isotopic ratios with12057513C (CO2) = minus23permil 12057513C (CH4) = minus61permil and 120575D (CH4) =minus93permil We do not have any explanation for this but do nothave any reasons either to consider it as an outlier
42 Major and Minor Elements Major and minor elementsmeasurements data are compiled in Table 3 Fluids fromFatu Kapa all exhibited a higher salinity than seawater up to46 wt NaCl whereas at Kulo Lasi fluids with both lower(28 wt NaCl) and higher (43 wt NaCl) salinity weresampled Mg and SO4 concentrations tend to be zero in thepurest samples at Fatu Kapa But the purest fluids from KuloLasi showed significant levels of Mg and SO4 associated withan extremely acidic pH (lt25) and a high119879 (343∘C) Althoughwe cannot totally discard that some mixing with seawateroccurred endmember concentrations of the Kulo Lasi fluidswere then estimated to be close to the purest fluids sampledwhereas they were obtained from mixing lines at Fatu Kapaassuming Mg zero (Table 5)
Fluids from Fatu Kapa were enriched compared to sea-water in alkali alkaline Earth and transition metals as wellas in strontium bromide and silica Conversely the fluidsfrom Kulo Lasi exhibited a much more complex patternThey were all highly enriched in transition metals and silicacompared to seawater and fluids from Fatu Kapa (eg Fe upto sim10mM) The enrichment versus seawater in alkali metalswas not as striking as for Fatu Kapa fluids As for the alkalineEarth metals the amount of Ca was identical to seawater andfluids were depleted in Sr compared to seawater Finally bothdepletion and enrichment in Br were observed in the fluidsfrom Kulo Lasi
43 Organic Geochemistry First of all we would like to men-tion that because solubility of organic compounds decreaseswith119879 and because samples were processed at room tempera-ture the measured concentrations are probably lower than insitu concentrations Moreover it is very likely that a portionof theOMwas adsorbed on small particles in the fluids whichare not taken into account using our extraction and analyticaltechniques As a result the concentrations we report hereprobably represent lower estimates of in situ concentrationsHowever since in situ measurement techniques are notavailable yet these values are the best estimates we can obtainNote that they also are the first to be published for SVOCs
Formate and acetate reached 163 and 155 120583M respec-tively and covaried withMg in the Kulo Lasi fluids (Figure 4)Concentrations of formate and acetate were significantlyhigher in the Fatu Kapa area but no correlation with Mgcould be observed Nevertheless the purest fluids usuallyshowed the highest concentrations Formate reached 68 ppbat Stephanie and 722 ppb at Fati Ufu whereas it could notbe detected at IdefX and Tutafi and was not measured at
6 GeofluidsTa
ble3Measuredconcentrationof
major
andminor
elem
entsin
hydrotherm
alflu
idsfrom
theKu
loLasiandFatu
Kapa
vent
fieldsFU
X-PL
YY-TiD
ZandFU
X-PL
YY-TiGZarereplicate
samplestakenin
thesam
eorifi
ceone
aftertheo
therbut
using2
individu
alTi
syrin
ges119879m
ax(chimney)isthem
axim
um119879o
fthe
discharged
fluidforthe
givenchim
neyw
hich
wasrecorded
bythe119879
prob
eofthe
subm
arineb
efores
ampling119879m
ax(sam
ple)isthem
axim
um119879o
fthe
fluid
enterin
gthes
ampler
recorded
durin
gsamplingby
thea
uton
omou
ssensorthatw
ascoup
led
atthen
ozzle
ofthes
ampler
Sample
name
Zone
Site
Descriptio
nDepth119879max
(sam
ple)
∘C
119879max
(chimney)
∘C
pHd20
Kgmminus3
S permilNaC
l(w
t)
Cl mM
Si mM
SO4
mM
Br 120583MNa
mM
K mM
Mg
mM
Ca mM
Li 120583MLi 120583M
Rb 120583MSr 120583M
Fe 120583MMn120583M
Cu 120583MZn 120583M
NaCl
BrC
ltimes103
NaK
CH4M
n
IAPS
O-
-Standard
water
--
--
-35
32
546
00
282
839
468
102
532
103
2727
1390ltLO
DltLO
DltLO
DltLO
D09
1546
-FU
-PL-05-
TiG2
KuloLasi
South(out)
Referencew
ater
1150
--
-10
2335
32
551
01
290
833
457
98532
106
2528
44
93ltLO
DltLO
DltLO
DltLO
D083
1547
-
FU-PL-05-
TiG1
KuloLasi
South(in
)Diffusefl
uidabove
worms
1414
328
-596
1023
3532
549
02
293
833
457
99532
106
2852
46
92ltLO
DltLO
D14
15083
1546
-
FU-PL-06-
TiG4
KuloLasi
North
(in)
Beehivetypeb
lack
smoker
1475
1341
332
607
1022
3330
516
10270
822
448
106
498
105
3354
53
84123
3217
31
087
1642
-
FU-PL-06-
TiD4
KuloLasi
North
(in)
Beehivetypeb
lack
smoker
1475
136
332
558
1021
3128
485
21
239
994
406
95457
102
3255
61
7478
7613
15084
20
430010
FU-PL-06-
TiG3
KuloLasi
North
(in)
Translu
cent
smoker
1475
3423
3307
224
1017
3229
497
82
88
738
388
185
246
116
149
156
2673
4796
862
1445
078
1521
0007
FU-PL-06-
TiD3
KuloLasi
North
(in)
Translu
cent
smoker
1475
3377
3307
237
1018
3330
517
84
107
770
405
166
286
108
115149
2494
4283
788
42
41078
1524
-
FU-PL-06-
TiD1
KuloLasi
North
(in)
Blacksm
oker
1475
3432
3451
236
102
4743
735
146
62
1135
612
295
265
109
238
249
4634
9884
1416
25
175
083
1521
-
FU-PL-06-
TiG1
KuloLasi
North
(in)
Blacksm
oker
1475
3432
3451
332
1028
4440
689
108
120
1051
565
237
349
108
176
197
3691
6845
1064
2077
082
1524
0001
FU3-PL
-03-
TiD3
Fatu
Kapa
20masf
Referencew
ater
1488
--
--
-33
565
00
288
841
483
104
545
107
2251
6ltLO
DltLO
DltLO
DltLO
DltLO
D085
1546
-
FU3-PL
-14-
TiG2
Fatu
Kapa
23masf
Referencew
ater
1572
2-
--
3633
557
00
287
841
477
104
542
108
23nm
nmnm
nmnm
nmnm
086
1546
-
FU3-PL
-04-
TiD3
Fatu
Kapa
Stephanie
Translu
cent
smoker
1554
213
279
465
103
4541
704
07
109
1300
519
398
187
696
472
568
80ltLO
D169
166
nmltLO
D074
1813
-
FU3-PL
-04-
TiG3
Fatu
Kapa
Stephanie
Translu
cent
smoker
1554
213
279
464
103
4440
686
10129
1240
513
365
225
628
420
504
71169
nm141
82ltLO
D075
1814
0805
FU3-PL
-08-
TiD1
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
289
280
410
3149
45
770
38
131574
535
542
08
989
705
804
121
268
655
265
66ltLO
D069
20
100886
FU3-PL
-08-
TiG1
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
289
280
341
1031
4945
772
47
07
1592
537
547
05
987
708
807
122
283
167
269
nmltLO
D070
21
100762
FU3-PL
-08-
TiD2
Fatu
Kapa
Stephanie
Translu
cent
smoker
1555
291
280
383
1031
4844
748
43
05
1537
520
529
06
953
684
806
116ltLO
D148
259
nmltLO
D070
21
10-
FU3-PL
-09-
TiD2
Fatu
Kapa
Stephanie
Beehivetypeb
lack
smoker
+bacterial
mat
1650
197
236
519
1026
4037
629
17198
1052
500
244
374
378
230
293
36149
nm65
nm10
079
1721
0902
FU3-PL
-09-
TiG2
Fatu
Kapa
Stephanie
Beehivetypeb
lack
smoker
+bacterial
mat
1559
197
236
542
1025
3835
600
10238
959
489
185
443
264
143
193
23ltLO
Dnm
23nmltLO
D081
1626
-
FU3-PL
-06-
TiD1
Fatu
Kapa
Carla
Translu
cent
smoker
1663
278
270
503
1024
3734
576
17185
927
482
285
352
179
260
310
42101
nmnm
nmltLO
D084
1617
-
FU3-PL
-06-
TiG1
Fatu
Kapa
Carla
Translu
cent
smoker
1663
278
270
491
1024
3734
579
07
127
984
476
378
236
222
391
455
63ltLO
D18
32nmltLO
D082
1713
-
FU3-PL
-08-
TiD3
Fatu
Kapa
Carla
Translu
cent
smoker
1664
281
281
278
1024
3835
594
45
11113
9479
596
04
315
690
746
104
115nm
48nm
44
080
198
1365
FU3-PL
-08-
TiG3
Fatu
Kapa
Carla
Translu
cent
smoker
1664
281
281
417
1024
3835
592
40
19112
0477
577
27
303
655
720
96ltLO
D288
39nmltLO
D081
198
-
FU3-PL
-11-
TiD3
Fatu
Kapa
IdefX
Translu
cent
smoker
1573
259
258
49
1025
4137
637
1483
1142
509
498
155
350
541
612
78ltLO
D38
26nmltLO
D080
1810
-
FU3-PL
-11-
TiG3
Fatu
Kapa
IdefX
Translu
cent
smoker
1573
259
258
443
1025
4339
664
41
191268
518
635
20
447
733
802
110160
nm46
nm25
078
198
1848
Geofluids 7
Table3Con
tinued
Sample
name
Zone
Site
Descriptio
nDepth119879max
(sam
ple)
∘C
119879max
(chimney)
∘C
pHd20
Kgmminus3
S permilNaC
l(w
t)
Cl mM
Si mM
SO4
mM
Br 120583MNa
mM
K mM
Mg
mM
Ca mM
Li 120583MLi 120583M
Rb 120583MSr 120583M
Fe 120583MMn120583M
Cu 120583MZn 120583M
NaCl
BrC
ltimes103
NaK
CH4M
n
FU3-PL
-14-
TiD1
Fatu
Kapa
IdefX
Translu
cent
smoker
1572
271
271
373
1025
4339
665
42
111282
519
662
08
434
764
823
120
144
2864
nm34
078
198
1078
FU3-PL
-14-
TiG1
Fatu
Kapa
IdefX
Translu
cent
smoker
1572
271
271
397
1025
4239
661
41
08
1279
515
657
08
429
757
825
119ltLO
Dnm
62nmltLO
D078
198
-
FU3-PL
-14-
TiD2
Fatu
Kapa
ObelX
Translu
cent
smoker
1669
272
-459
103
4945
769
45
07
1506
577
694
13655
757
nmnm
nmnm
nmnm
nm075
20
8-
FU3-PL
-14-
TiD3
Fatu
Kapa
ObelX
Translu
cent
smoker
1636
287
-428
103
4743
729
37
150
1283
557
588
111
650
621
nmnm
nmnm
nmnm
nm076
189
-
FU3-PL
-14-
TiG3
Fatu
Kapa
ObelX
Translu
cent
smoker
1636
287
-537
1028
4339
672
25
270
1103
528
425
253
546
415
nmnm
nmnm
nmnm
nm079
1612
-
FU3-PL
-18-
TiD1
Fatu
Kapa
AsterX
Translu
cent
smoker
1540
265
260
435
1027
4441
693
37
101344
533
649
12511
755
nmnm
nmnm
nmnm
nm077
198
-
FU3-PL
-17-
TiD2
Fatu
Kapa
FatiUfu
Greysm
oker
1522
299
303
426
1031
4743
739
33
931378
555
384
176
666
543
nmnm
nmnm
nmnm
nm075
1914
-
FU3-PL
-17-
TiG2
Fatu
Kapa
FatiUfu
Greysm
oker
1522
299
303
422
1031
4844
748
35
87
1402
562
398
159
697
569
nmnm
nmnm
nmnm
nm075
1914
-
FU3-PL
-21-
TiD1
Fatu
Kapa
FatiUfu
Greysm
oker
1523
302
301
381
1032
5046
784
47
141554
577
473
14862
717
nmnm
nmnm
nmnm
nm074
20
12-
FU3-PL
-21-
TiG1
Fatu
Kapa
FatiUfu
Greysm
oker
1523
302
301
469
103
4541
708
27
105
1292
544
347
193
603
474
nmnm
nmnm
nmnm
nm077
1816
-
FU3-PL
-21-
TiD2
Fatu
Kapa
FatiUfu
Whitesm
oker
1503
-284
327
1028
4441
694
49
04
1359
534
393
10633
573
nmnm
nmnm
nmnm
nm077
20
14-
FU3-PL
-21-
TiG2
Fatu
Kapa
FatiUfu
Whitesm
oker
1503
-284
422
1026
4239
661
39
701217
520
320
133
506
435
nmnm
nmnm
nmnm
nm079
1816
-
FU3-PL
-20-
TiD1
Fatu
Kapa
Tutafi
Greysm
oker
1580
316
317
41
1029
4642
720
26
06
1409
543
546
09
654
628
nmnm
nmnm
nmnm
nm075
20
10-
FU3-PL
-20-
TiG1
Fatu
Kapa
Tutafi
Greysm
oker
1580
316
317
414
1029
4642
723
23
101409
543
547
07
664
630
nmnm
nmnm
nmnm
nm075
1910
-
FU3-PL
-21-
TiD3
Fatu
Kapa
Tutafi
Whitesm
oker
1626
293
294
292
1028
4541
701
51
09
1367
528
513
03
639
640
nmnm
nmnm
nmnm
nm075
1910
-
FU3-PL
-21-
TiG3
Fatu
Kapa
Tutafi
Whitesm
oker
1626
293
294
365
1027
4541
700
50
08
1371
528
510
08
633
633
nmnm
nmnm
nmnm
nm075
20
10-
8 Geofluids
Table4
Measuredgascon
centratio
nandassociated
stableiso
topicratiosh
ydrothermalflu
idsfromtheK
uloL
asiand
FatuKa
paventfieldsVa
luesoflogfH2werec
alculated
usingS
UPC
RT92
with
thes
lop9
8database
Samplen
ame
Site
H2S
N2
3He
RRa
H2
logfH2
CH4
CO2
C 2H6
C 2H4
C 3H8
C 3H6
n-C 4
H10n-C 5
H12120575D(H2)120575D(C
H4)12057513C(C
O2)12057513C(C
H4)12057513C(C2H6)12057513C(C3H8)12057513C(C4H10)
mM
mM
mM
mM
mM
mM120583M120583M120583M120583M120583M
120583M
permilpermil
permilpermil
permilpermil
permilSeaw
ater
059
nmnmltLO
D-ltLO
D23
nmnm
nmnm
nmnm
nmnm
nmnm
nmnm
nmFU
-PL-05-TiG1
KuloLasi
012
nmnmltLO
Q-
0001
26ltLO
DnmltLO
DnmltLO
DltLO
Dnm
nmnm
nmnm
nmnm
FU-PL-06-TiD
4Ku
loLasi
166
010
nmnm
114
-0001
13002
0005
000
6000
40005
0005minus323
nm
minus32
minus29
minus27
minus26
nmFU
-PL-06-TiG3
KuloLasi
505
143
nmnm
198minus311
000
651
011
004
20028
0030
0024
000
6minus306
nm
minus41
minus23
minus26
minus26
minus24
FU-PL-06-TiD
1Ku
loLasi
039
248
nmnm
618minus362
000
430
01
0017
0017
0020
0012
000
4minus300
nm
minus19
minus28
minus24
minus26
minus24
FU-PL-06-TiG1
KuloLasi
079
nmnm
104minus440
0001
10002
000
90005
0007
0005
0001minus316
nm
minus02
minus272
minus22
minus26
minus24
FU3-PL
-04-TiG3
Stephanie
091
09311119864minus08
86
003minus18
70114
155ltLO
DltLO
DltLO
DltLO
DltLO
D17
nmnm
nmnm
nmnm
nmFU
3-PL
-08-TiD1
Stephanie
123
198
nm006minus15
70235
290ltLO
DltLO
DltLO
DltLO
DltLO
D32minus676minus108
minus5
minus217
nmnm
nmFU
3-PL
-08-TiG1
Stephanie
098
24744119864minus09
76005minus16
50205
257ltLO
DltLO
DltLO
DltLO
DltLO
D29
nmnm
nmnm
nmnm
nmFU
3-PL
-09-TiD2
Stephanie
023
04819119864minus09
70004minus17
50059
60ltLO
DltLO
DltLO
DltLO
DltLO
D07minus436minus111
minus53
minus222
nmnm
nmFU
3-PL
-06-TiD1
Carla
134
05071119864minus09
96001minus235
0021
45ltLO
DltLO
DltLO
DltLO
DltLO
D05
nmnm
nmnm
nmnm
nmFU
3-PL
-08-TiD3
Carla
019
33317119864minus08
98005minus16
5006
6119ltLO
DltLO
DltLO
DltLO
DltLO
D15
minus410minus109
minus47
minus215
nmnm
nmFU
3-PL
-11-T
iG3
Idef
X113
07818119864minus08
98003minus18
70085
100ltLO
DltLO
DltLO
DltLO
DltLO
D11
nmnm
nmnm
nmnm
nmFU
3-PL
-14-TiD1
Idef
X10
012
055119864minus09
87
002minus205
0069
101ltLO
DltLO
DltLO
DltLO
DltLO
D11
minus417minus110
minus49
minus238
nmnm
nmFU
3-PL
-14-TiD2
ObelX
085
10538119864minus08
98003minus18
70110
87ltLO
DltLO
DltLO
DltLO
DltLO
D10
minus40
7minus113
minus5
minus24
nmnm
nmFU
3-PL
-14-TiD3
ObelX
054
09352119864minus09
84
002minus205
0165
92ltLO
DltLO
DltLO
DltLO
DltLO
D10
nmnm
nmnm
nmnm
nmFU
3-PL
-18-TiD1
AsterX
098
089
nmnm
001minus235
0067
92ltLO
DltLO
DltLO
DltLO
DltLO
D10
minus412minus111
minus49
minus236
nmnm
nmFU
3-PL
-17-TiG2
FatiUfu
176
08427119864minus08
99001minus259
0070
215ltLO
DltLO
DltLO
DltLO
DltLO
D23
-minus93
minus23
minus61
nmnm
nmFU
3-PL
-21-T
iD2
FatiUfu
071
20731119864minus09
99003minus211
0111
126ltLO
DltLO
DltLO
DltLO
DltLO
D15
minus410minus109
minus44
minus233
nmnm
nmFU
3-PL
-20-TiD1
Tutafi
236
11814119864minus08
92005minus18
90156
222ltLO
DltLO
DltLO
DltLO
DltLO
D24minus396minus111
minus45
minus236
nmnm
nmFU
3-PL
-21-T
iD3
Tutafi
084
167
nmnm
003minus211
0053
117ltLO
DltLO
DltLO
DltLO
DltLO
D14
minus415minus109
minus47
minus242
nmnm
nm
Geofluids 9
Table5En
dmem
bercom
positions
influ
idsfrom
theK
uloLasiandFatu
Kapa
vent
fieldsKu
loLasiendm
emberscann
otbe
extrapolated
atMg=
0Va
luespresentedhereforb
othbrinea
ndcond
ensedvapo
urph
ases
correspo
ndto
concentrations
inthefl
uidwith
thelow
estM
gElem
entalcom
positions
inendm
emberfl
uids
from
thev
arious
sites
oftheF
atuKa
pavent
field
were
calculated
usingthem
ixinglin
es(FigureS
1)andassumingMg=0Va
lues
ofthep
urestfl
uidwereu
sedwhenlin
earregressionwas
notp
ossib
le(lowast)Notethato
nlyon
esam
plew
asavailable
forthe
AsterX
site(1)
Zone
Site
Depth119879
pHNaC
lCl
SiSO
4Br
Na
KMg
CaLi
RbSr
FeMn
CuZn
NaCl
BrC
lNaK
CH4Mn
∘ C(w
t)
mM
mM
mM120583M
mM
mM
mM
mM120583M120583M120583M
120583M120583M
120583M120583M
times103
KuloLasi
NaC
lpoo
r1475
345
224
29
497
82
88
738
388
185
246
116
149
2673
4796
862
1445
078
148
210007lowast
KuloLasi
NaC
lrich
1475
345
236
43
735
146
62
1135
612
295
265
109
238
4634
9884
1416
25
175
083
154
210001lowast
Fatu
Kapa
Stephanie
1555
280
34
45
767
47lowast
00
1569
532
545
00
989
708
114282lowast
655lowast
268
66lowastltL
OD
069
205
10076lowast
Fatu
Kapa
Carla
1664
280
28
35
594
43
00
1132
477
599
00
314
691
105
114lowast
287lowast
53nm
44lowast
080
190
813
7lowast
Fatu
Kapa
Idef
X1572
270
37
39
665
42lowast
00
1282
518
664
00
443
751
113
160lowast
28lowast
60nm
34lowast
078
193
810
8lowast
Fatu
Kapa
ObelX
1669
270
46
45
771
46
00
1458
580
710
00
859
777
nmnm
nmnm
nmnm
075
189
8-
Fatu
Kapa
AsterX(1)
1540
265
44
41
693
37
101344
533
649
12511
755
nmnm
nmnm
nmnm
077
194
8-
Fatu
Kapa
FatiUfu
1523
300
38
46
790
49
00
1589
580
482
00
854
722
nmnm
nmnm
nmnm
073
201
12-
Fatu
Kapa
FatiUfu
1503
280
33
41
700
49
00
1380
538
400
00
650
583
nmnm
nmnm
nmnm
077
197
13-
Fatu
Kapa
Tutafi
1580
315
41
42
713
51
00
1405
535
529
00
651
635
nmnm
nmnm
nmnm
075
197
10-
IAPS
OStandard
sw-
--
32
546
00
282
839
468
102
532
103
2713
90ltLO
DltLO
DltLO
DltLO
D09
1546
-Ku
loLasi
References
w1150
--
32
551
01
290
833
457
98532
106
2544
93ltLO
DltLO
DltLO
DltL
OD
083
1547
-Fatu
Kapa
References
w1488
--
33
565
00
288
841
483
104
545
107
2258ltLO
DltLO
DltLO
DltLO
DltL
OD
085
1546
-Fatu
Kapa
References
w1572
2-
33
557
00
287
841
477
104
542
108
23nm
nmnm
nmnm
nm086
1546
-lowastMaxim
umvaluew
henlin
earregressionwas
notp
ossib
le(1)on
lyon
esam
ple
10 Geofluids
(a)
(b)
(c)
Figure 3 (a) and (b) Photographs of anhydrite structures observed at Stephanie Carla IdefX AsterX and ObelX site (c) Photographs of greysmokers associated with sulphides structures observed at Fati Ufu and Tutafi Copyrights from Ifremer FUTUNA 3 cruise
02468
1012141618
0 10 20 30 40 50 60Mg (mM)
Kulo Lasi
AcetateFormate
SW-acetateSW-formate
Con
cent
ratio
n(
M)
Figure 4 Mixing lines of formate and acetate versus Mg for the Kulo Lasi fluids Note that the reference deep-sea water sample (FU-PL05-TiG2 noted as SW here) was taken at 1150m depth above the southern wall of the caldera (see Figure 1 for location and Table 3) and thus verylikely within the plume [7] This would account for the unusual concentrations of formate and acetate detected
Geofluids 11
Carla Acetate was detected in all analysed samples andconcentrations were an order of magnitude higher than theones of formate (543ndash2309 ppb) (Table 6)
Heavier extractable organic compounds were notdetected in the dry control experiment and only a few weredetectable but below limit of quantification (LOQ) in theMQ water blank experiment (Table 6) This showed thatsample preparation and storage could be considered ascontamination-free steps The levels of heavier extractableorganic compounds appeared rather high in the referencewater at Fatu Kapa certainly because of the overall spreadhydrothermal discharges and diffuse venting in the region [7](Table 6 Figure 5) This sample was indeed taken mid-waybetween ObelX and AsterX fields at about 20m above theseafloor As a consequence it is difficult to assess possiblecontamination originating from sampling device or seawatercontribution in the present case However earlier studieshave shown that they generally did not represent majorsources of contamination as for the studied compounds[27 37] Nevertheless in comparison to deep-sea waterboth the qualitative (Kulo Lasi) and quantitative (FatuKapa) data obtained suggested enrichment of the fluidsin hydrothermally derived compounds namely n-alkanes(C9ndashC12) n-FAs (C9 C12 C14ndashC18) and PAHs (fluorenephenanthrene pyrene) ([39] Table 6 Figures 5 and 6)Such enrichment was unclear for gtC12 n-alkanes C10C11 C13 n-FAs BTEXs naphthalene acenaphthene andfluoranthene because of their very low concentration andorthe measurement uncertainty
Differences in concentrations seemed to exist among thevents over the Fatu Kapa area Fluids from the Stephanie ventfield had concentrations in hydrocarbons equal or below thereference water sample whereas they were clearly enrichedin C9 C12 C14ndashC18 n-FAs The Carla fluids were slightlyenriched in C9ndashC12 n-alkanes and showed the highest con-centrations in PAHs Fluids from IdefX Fati Ufu and Tutafishared some similarities a strong enrichment in decane andundecane alike concentrations in PAHs and the presence ofsignificant amounts of xylene However fluids expelled at theTutafi vent appeared the most enriched in C9ndashC11 n-alkanesand xylenes In terms of fatty acids and considering theanalytical error the 5 vents showed consistent concentrationswith C9 C16 and C18 being major Note that fluids from FatiUfu seemed depleted in C17 and C18
Generally we did not observe strong linear correlationbetween the concentration of individual compounds andMgNonetheless these relations showed that both enrichmentand depletion of organic compounds seemed to occur inhydrothermal fluids versus deep-sea water
5 Discussion
The elemental and gas composition of hydrothermal fluidsis mainly affected by waterrock interactions and thus thenature of the host rocks phase separation magmatic fluidcontribution conductive cooling and seawater mixing inlocal recharge zones [45] In the following discussion weattempt to unravel the occurrence of these various processes
both at Kulo Lasi and at Fatu Kapa Much less is known onprocesses that control organic geochemistry and are thereforediscussed here as well as some implications of the presenceof organic compounds in hydrothermal fluids Implicationsrelated to the composition of the fluids are dependent onfluxes therefore we give here an attempt to provide order ofmagnitude estimates of heat and mass fluxes
51 Plume-Fluids Relations The geochemistry and dynamicsof the plumes over the Wallis and Futuna region havebeen studied elsewhere [7] The Kulo Lasi plume has beenproposed to be the result of both high-119879 and diffuse ventingfrom multiple vents located both on the floor and on thewall of the caldera Consistently both types of venting havebeen observed [6] Helium nephelometry and Mn profilesrecorded above the northern sampling area showed constantelevated concentrations in the 300masf and were assumedto be the results of diffuse venting Our results show thatthey are obviously the result of the numerous small blacksmokers observed on the seafloor (Figure 2) The methaneconcentration in the sampled fluids was extremely low whichcannot account for the elevated concentration of CH4 inthe water column reported by Konn et al [7] The strongdifference in the CH4Mn ratios between the plume (07ndash45)and the sampled fluids (0001ndash001) is another line of evidencethat the methane plume has another origin compared tohydrothermal fluids and likely come from degassing of thelava flows as suggested by the authors Although other fluiddischarges likely remain undiscovered this is consistent witha past eruption and accumulation of the water mass in thecaldera [39]
A great diversity of the fluid compositions was expectedfrom the geological settings and the water column survey andwas indeed confirmed by the mixing lines that point to asmany endmembers as sampled areas (Figure S1) CH4TDMratios also differed among the vents but it was not due to soleCH4 concentration variations as suggested earlier (Table 5)[7] Finally the very weak nephelometry of the Fatu Kapaplume is likely best explained by the low metal contents ofthe fluids
52 Reaction Zone Depth The solubility of Quartz in hydro-thermal fluids has been studied by different authors (eg[46]) According to these works silica concentration in thefluid may be used to estimate the depth of the reaction zoneThe silica concentration measured in the Kulo Lasi and FatuKapa fluids indicates a hydrothermal reaction zone at seaflooror in thewater column (Figure S2) Both observations suggestthat in this area fluids are not in equilibria with Quartz atthe pressure and temperature of the fluid emission And thisprevents using Si as a geothermometer to determine the depthof the reaction zone
All fluids at Fatu Kapa were indeed highly depleted inSi with respect to the Quartz saturation curve at 170 bar300∘C (Si sim12mM in Figure S2) A higher temperature inthe reaction zone (gt350∘C at 200 bar) may explain a lower Siconcentration in the fluid at equilibrium as Quartz solubilitydecreases (Figure S2) The dispersion of a great number of
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
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[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
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[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
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[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
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[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
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[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Figure 3 (a) and (b) Photographs of anhydrite structures observed at Stephanie Carla IdefX AsterX and ObelX site (c) Photographs of greysmokers associated with sulphides structures observed at Fati Ufu and Tutafi Copyrights from Ifremer FUTUNA 3 cruise
02468
1012141618
0 10 20 30 40 50 60Mg (mM)
Kulo Lasi
AcetateFormate
SW-acetateSW-formate
Con
cent
ratio
n(
M)
Figure 4 Mixing lines of formate and acetate versus Mg for the Kulo Lasi fluids Note that the reference deep-sea water sample (FU-PL05-TiG2 noted as SW here) was taken at 1150m depth above the southern wall of the caldera (see Figure 1 for location and Table 3) and thus verylikely within the plume [7] This would account for the unusual concentrations of formate and acetate detected
Geofluids 11
Carla Acetate was detected in all analysed samples andconcentrations were an order of magnitude higher than theones of formate (543ndash2309 ppb) (Table 6)
Heavier extractable organic compounds were notdetected in the dry control experiment and only a few weredetectable but below limit of quantification (LOQ) in theMQ water blank experiment (Table 6) This showed thatsample preparation and storage could be considered ascontamination-free steps The levels of heavier extractableorganic compounds appeared rather high in the referencewater at Fatu Kapa certainly because of the overall spreadhydrothermal discharges and diffuse venting in the region [7](Table 6 Figure 5) This sample was indeed taken mid-waybetween ObelX and AsterX fields at about 20m above theseafloor As a consequence it is difficult to assess possiblecontamination originating from sampling device or seawatercontribution in the present case However earlier studieshave shown that they generally did not represent majorsources of contamination as for the studied compounds[27 37] Nevertheless in comparison to deep-sea waterboth the qualitative (Kulo Lasi) and quantitative (FatuKapa) data obtained suggested enrichment of the fluidsin hydrothermally derived compounds namely n-alkanes(C9ndashC12) n-FAs (C9 C12 C14ndashC18) and PAHs (fluorenephenanthrene pyrene) ([39] Table 6 Figures 5 and 6)Such enrichment was unclear for gtC12 n-alkanes C10C11 C13 n-FAs BTEXs naphthalene acenaphthene andfluoranthene because of their very low concentration andorthe measurement uncertainty
Differences in concentrations seemed to exist among thevents over the Fatu Kapa area Fluids from the Stephanie ventfield had concentrations in hydrocarbons equal or below thereference water sample whereas they were clearly enrichedin C9 C12 C14ndashC18 n-FAs The Carla fluids were slightlyenriched in C9ndashC12 n-alkanes and showed the highest con-centrations in PAHs Fluids from IdefX Fati Ufu and Tutafishared some similarities a strong enrichment in decane andundecane alike concentrations in PAHs and the presence ofsignificant amounts of xylene However fluids expelled at theTutafi vent appeared the most enriched in C9ndashC11 n-alkanesand xylenes In terms of fatty acids and considering theanalytical error the 5 vents showed consistent concentrationswith C9 C16 and C18 being major Note that fluids from FatiUfu seemed depleted in C17 and C18
Generally we did not observe strong linear correlationbetween the concentration of individual compounds andMgNonetheless these relations showed that both enrichmentand depletion of organic compounds seemed to occur inhydrothermal fluids versus deep-sea water
5 Discussion
The elemental and gas composition of hydrothermal fluidsis mainly affected by waterrock interactions and thus thenature of the host rocks phase separation magmatic fluidcontribution conductive cooling and seawater mixing inlocal recharge zones [45] In the following discussion weattempt to unravel the occurrence of these various processes
both at Kulo Lasi and at Fatu Kapa Much less is known onprocesses that control organic geochemistry and are thereforediscussed here as well as some implications of the presenceof organic compounds in hydrothermal fluids Implicationsrelated to the composition of the fluids are dependent onfluxes therefore we give here an attempt to provide order ofmagnitude estimates of heat and mass fluxes
51 Plume-Fluids Relations The geochemistry and dynamicsof the plumes over the Wallis and Futuna region havebeen studied elsewhere [7] The Kulo Lasi plume has beenproposed to be the result of both high-119879 and diffuse ventingfrom multiple vents located both on the floor and on thewall of the caldera Consistently both types of venting havebeen observed [6] Helium nephelometry and Mn profilesrecorded above the northern sampling area showed constantelevated concentrations in the 300masf and were assumedto be the results of diffuse venting Our results show thatthey are obviously the result of the numerous small blacksmokers observed on the seafloor (Figure 2) The methaneconcentration in the sampled fluids was extremely low whichcannot account for the elevated concentration of CH4 inthe water column reported by Konn et al [7] The strongdifference in the CH4Mn ratios between the plume (07ndash45)and the sampled fluids (0001ndash001) is another line of evidencethat the methane plume has another origin compared tohydrothermal fluids and likely come from degassing of thelava flows as suggested by the authors Although other fluiddischarges likely remain undiscovered this is consistent witha past eruption and accumulation of the water mass in thecaldera [39]
A great diversity of the fluid compositions was expectedfrom the geological settings and the water column survey andwas indeed confirmed by the mixing lines that point to asmany endmembers as sampled areas (Figure S1) CH4TDMratios also differed among the vents but it was not due to soleCH4 concentration variations as suggested earlier (Table 5)[7] Finally the very weak nephelometry of the Fatu Kapaplume is likely best explained by the low metal contents ofthe fluids
52 Reaction Zone Depth The solubility of Quartz in hydro-thermal fluids has been studied by different authors (eg[46]) According to these works silica concentration in thefluid may be used to estimate the depth of the reaction zoneThe silica concentration measured in the Kulo Lasi and FatuKapa fluids indicates a hydrothermal reaction zone at seaflooror in thewater column (Figure S2) Both observations suggestthat in this area fluids are not in equilibria with Quartz atthe pressure and temperature of the fluid emission And thisprevents using Si as a geothermometer to determine the depthof the reaction zone
All fluids at Fatu Kapa were indeed highly depleted inSi with respect to the Quartz saturation curve at 170 bar300∘C (Si sim12mM in Figure S2) A higher temperature inthe reaction zone (gt350∘C at 200 bar) may explain a lower Siconcentration in the fluid at equilibrium as Quartz solubilitydecreases (Figure S2) The dispersion of a great number of
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
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[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
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[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Figure 3 (a) and (b) Photographs of anhydrite structures observed at Stephanie Carla IdefX AsterX and ObelX site (c) Photographs of greysmokers associated with sulphides structures observed at Fati Ufu and Tutafi Copyrights from Ifremer FUTUNA 3 cruise
02468
1012141618
0 10 20 30 40 50 60Mg (mM)
Kulo Lasi
AcetateFormate
SW-acetateSW-formate
Con
cent
ratio
n(
M)
Figure 4 Mixing lines of formate and acetate versus Mg for the Kulo Lasi fluids Note that the reference deep-sea water sample (FU-PL05-TiG2 noted as SW here) was taken at 1150m depth above the southern wall of the caldera (see Figure 1 for location and Table 3) and thus verylikely within the plume [7] This would account for the unusual concentrations of formate and acetate detected
Geofluids 11
Carla Acetate was detected in all analysed samples andconcentrations were an order of magnitude higher than theones of formate (543ndash2309 ppb) (Table 6)
Heavier extractable organic compounds were notdetected in the dry control experiment and only a few weredetectable but below limit of quantification (LOQ) in theMQ water blank experiment (Table 6) This showed thatsample preparation and storage could be considered ascontamination-free steps The levels of heavier extractableorganic compounds appeared rather high in the referencewater at Fatu Kapa certainly because of the overall spreadhydrothermal discharges and diffuse venting in the region [7](Table 6 Figure 5) This sample was indeed taken mid-waybetween ObelX and AsterX fields at about 20m above theseafloor As a consequence it is difficult to assess possiblecontamination originating from sampling device or seawatercontribution in the present case However earlier studieshave shown that they generally did not represent majorsources of contamination as for the studied compounds[27 37] Nevertheless in comparison to deep-sea waterboth the qualitative (Kulo Lasi) and quantitative (FatuKapa) data obtained suggested enrichment of the fluidsin hydrothermally derived compounds namely n-alkanes(C9ndashC12) n-FAs (C9 C12 C14ndashC18) and PAHs (fluorenephenanthrene pyrene) ([39] Table 6 Figures 5 and 6)Such enrichment was unclear for gtC12 n-alkanes C10C11 C13 n-FAs BTEXs naphthalene acenaphthene andfluoranthene because of their very low concentration andorthe measurement uncertainty
Differences in concentrations seemed to exist among thevents over the Fatu Kapa area Fluids from the Stephanie ventfield had concentrations in hydrocarbons equal or below thereference water sample whereas they were clearly enrichedin C9 C12 C14ndashC18 n-FAs The Carla fluids were slightlyenriched in C9ndashC12 n-alkanes and showed the highest con-centrations in PAHs Fluids from IdefX Fati Ufu and Tutafishared some similarities a strong enrichment in decane andundecane alike concentrations in PAHs and the presence ofsignificant amounts of xylene However fluids expelled at theTutafi vent appeared the most enriched in C9ndashC11 n-alkanesand xylenes In terms of fatty acids and considering theanalytical error the 5 vents showed consistent concentrationswith C9 C16 and C18 being major Note that fluids from FatiUfu seemed depleted in C17 and C18
Generally we did not observe strong linear correlationbetween the concentration of individual compounds andMgNonetheless these relations showed that both enrichmentand depletion of organic compounds seemed to occur inhydrothermal fluids versus deep-sea water
5 Discussion
The elemental and gas composition of hydrothermal fluidsis mainly affected by waterrock interactions and thus thenature of the host rocks phase separation magmatic fluidcontribution conductive cooling and seawater mixing inlocal recharge zones [45] In the following discussion weattempt to unravel the occurrence of these various processes
both at Kulo Lasi and at Fatu Kapa Much less is known onprocesses that control organic geochemistry and are thereforediscussed here as well as some implications of the presenceof organic compounds in hydrothermal fluids Implicationsrelated to the composition of the fluids are dependent onfluxes therefore we give here an attempt to provide order ofmagnitude estimates of heat and mass fluxes
51 Plume-Fluids Relations The geochemistry and dynamicsof the plumes over the Wallis and Futuna region havebeen studied elsewhere [7] The Kulo Lasi plume has beenproposed to be the result of both high-119879 and diffuse ventingfrom multiple vents located both on the floor and on thewall of the caldera Consistently both types of venting havebeen observed [6] Helium nephelometry and Mn profilesrecorded above the northern sampling area showed constantelevated concentrations in the 300masf and were assumedto be the results of diffuse venting Our results show thatthey are obviously the result of the numerous small blacksmokers observed on the seafloor (Figure 2) The methaneconcentration in the sampled fluids was extremely low whichcannot account for the elevated concentration of CH4 inthe water column reported by Konn et al [7] The strongdifference in the CH4Mn ratios between the plume (07ndash45)and the sampled fluids (0001ndash001) is another line of evidencethat the methane plume has another origin compared tohydrothermal fluids and likely come from degassing of thelava flows as suggested by the authors Although other fluiddischarges likely remain undiscovered this is consistent witha past eruption and accumulation of the water mass in thecaldera [39]
A great diversity of the fluid compositions was expectedfrom the geological settings and the water column survey andwas indeed confirmed by the mixing lines that point to asmany endmembers as sampled areas (Figure S1) CH4TDMratios also differed among the vents but it was not due to soleCH4 concentration variations as suggested earlier (Table 5)[7] Finally the very weak nephelometry of the Fatu Kapaplume is likely best explained by the low metal contents ofthe fluids
52 Reaction Zone Depth The solubility of Quartz in hydro-thermal fluids has been studied by different authors (eg[46]) According to these works silica concentration in thefluid may be used to estimate the depth of the reaction zoneThe silica concentration measured in the Kulo Lasi and FatuKapa fluids indicates a hydrothermal reaction zone at seaflooror in thewater column (Figure S2) Both observations suggestthat in this area fluids are not in equilibria with Quartz atthe pressure and temperature of the fluid emission And thisprevents using Si as a geothermometer to determine the depthof the reaction zone
All fluids at Fatu Kapa were indeed highly depleted inSi with respect to the Quartz saturation curve at 170 bar300∘C (Si sim12mM in Figure S2) A higher temperature inthe reaction zone (gt350∘C at 200 bar) may explain a lower Siconcentration in the fluid at equilibrium as Quartz solubilitydecreases (Figure S2) The dispersion of a great number of
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Figure 3 (a) and (b) Photographs of anhydrite structures observed at Stephanie Carla IdefX AsterX and ObelX site (c) Photographs of greysmokers associated with sulphides structures observed at Fati Ufu and Tutafi Copyrights from Ifremer FUTUNA 3 cruise
02468
1012141618
0 10 20 30 40 50 60Mg (mM)
Kulo Lasi
AcetateFormate
SW-acetateSW-formate
Con
cent
ratio
n(
M)
Figure 4 Mixing lines of formate and acetate versus Mg for the Kulo Lasi fluids Note that the reference deep-sea water sample (FU-PL05-TiG2 noted as SW here) was taken at 1150m depth above the southern wall of the caldera (see Figure 1 for location and Table 3) and thus verylikely within the plume [7] This would account for the unusual concentrations of formate and acetate detected
Geofluids 11
Carla Acetate was detected in all analysed samples andconcentrations were an order of magnitude higher than theones of formate (543ndash2309 ppb) (Table 6)
Heavier extractable organic compounds were notdetected in the dry control experiment and only a few weredetectable but below limit of quantification (LOQ) in theMQ water blank experiment (Table 6) This showed thatsample preparation and storage could be considered ascontamination-free steps The levels of heavier extractableorganic compounds appeared rather high in the referencewater at Fatu Kapa certainly because of the overall spreadhydrothermal discharges and diffuse venting in the region [7](Table 6 Figure 5) This sample was indeed taken mid-waybetween ObelX and AsterX fields at about 20m above theseafloor As a consequence it is difficult to assess possiblecontamination originating from sampling device or seawatercontribution in the present case However earlier studieshave shown that they generally did not represent majorsources of contamination as for the studied compounds[27 37] Nevertheless in comparison to deep-sea waterboth the qualitative (Kulo Lasi) and quantitative (FatuKapa) data obtained suggested enrichment of the fluidsin hydrothermally derived compounds namely n-alkanes(C9ndashC12) n-FAs (C9 C12 C14ndashC18) and PAHs (fluorenephenanthrene pyrene) ([39] Table 6 Figures 5 and 6)Such enrichment was unclear for gtC12 n-alkanes C10C11 C13 n-FAs BTEXs naphthalene acenaphthene andfluoranthene because of their very low concentration andorthe measurement uncertainty
Differences in concentrations seemed to exist among thevents over the Fatu Kapa area Fluids from the Stephanie ventfield had concentrations in hydrocarbons equal or below thereference water sample whereas they were clearly enrichedin C9 C12 C14ndashC18 n-FAs The Carla fluids were slightlyenriched in C9ndashC12 n-alkanes and showed the highest con-centrations in PAHs Fluids from IdefX Fati Ufu and Tutafishared some similarities a strong enrichment in decane andundecane alike concentrations in PAHs and the presence ofsignificant amounts of xylene However fluids expelled at theTutafi vent appeared the most enriched in C9ndashC11 n-alkanesand xylenes In terms of fatty acids and considering theanalytical error the 5 vents showed consistent concentrationswith C9 C16 and C18 being major Note that fluids from FatiUfu seemed depleted in C17 and C18
Generally we did not observe strong linear correlationbetween the concentration of individual compounds andMgNonetheless these relations showed that both enrichmentand depletion of organic compounds seemed to occur inhydrothermal fluids versus deep-sea water
5 Discussion
The elemental and gas composition of hydrothermal fluidsis mainly affected by waterrock interactions and thus thenature of the host rocks phase separation magmatic fluidcontribution conductive cooling and seawater mixing inlocal recharge zones [45] In the following discussion weattempt to unravel the occurrence of these various processes
both at Kulo Lasi and at Fatu Kapa Much less is known onprocesses that control organic geochemistry and are thereforediscussed here as well as some implications of the presenceof organic compounds in hydrothermal fluids Implicationsrelated to the composition of the fluids are dependent onfluxes therefore we give here an attempt to provide order ofmagnitude estimates of heat and mass fluxes
51 Plume-Fluids Relations The geochemistry and dynamicsof the plumes over the Wallis and Futuna region havebeen studied elsewhere [7] The Kulo Lasi plume has beenproposed to be the result of both high-119879 and diffuse ventingfrom multiple vents located both on the floor and on thewall of the caldera Consistently both types of venting havebeen observed [6] Helium nephelometry and Mn profilesrecorded above the northern sampling area showed constantelevated concentrations in the 300masf and were assumedto be the results of diffuse venting Our results show thatthey are obviously the result of the numerous small blacksmokers observed on the seafloor (Figure 2) The methaneconcentration in the sampled fluids was extremely low whichcannot account for the elevated concentration of CH4 inthe water column reported by Konn et al [7] The strongdifference in the CH4Mn ratios between the plume (07ndash45)and the sampled fluids (0001ndash001) is another line of evidencethat the methane plume has another origin compared tohydrothermal fluids and likely come from degassing of thelava flows as suggested by the authors Although other fluiddischarges likely remain undiscovered this is consistent witha past eruption and accumulation of the water mass in thecaldera [39]
A great diversity of the fluid compositions was expectedfrom the geological settings and the water column survey andwas indeed confirmed by the mixing lines that point to asmany endmembers as sampled areas (Figure S1) CH4TDMratios also differed among the vents but it was not due to soleCH4 concentration variations as suggested earlier (Table 5)[7] Finally the very weak nephelometry of the Fatu Kapaplume is likely best explained by the low metal contents ofthe fluids
52 Reaction Zone Depth The solubility of Quartz in hydro-thermal fluids has been studied by different authors (eg[46]) According to these works silica concentration in thefluid may be used to estimate the depth of the reaction zoneThe silica concentration measured in the Kulo Lasi and FatuKapa fluids indicates a hydrothermal reaction zone at seaflooror in thewater column (Figure S2) Both observations suggestthat in this area fluids are not in equilibria with Quartz atthe pressure and temperature of the fluid emission And thisprevents using Si as a geothermometer to determine the depthof the reaction zone
All fluids at Fatu Kapa were indeed highly depleted inSi with respect to the Quartz saturation curve at 170 bar300∘C (Si sim12mM in Figure S2) A higher temperature inthe reaction zone (gt350∘C at 200 bar) may explain a lower Siconcentration in the fluid at equilibrium as Quartz solubilitydecreases (Figure S2) The dispersion of a great number of
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Figure 3 (a) and (b) Photographs of anhydrite structures observed at Stephanie Carla IdefX AsterX and ObelX site (c) Photographs of greysmokers associated with sulphides structures observed at Fati Ufu and Tutafi Copyrights from Ifremer FUTUNA 3 cruise
02468
1012141618
0 10 20 30 40 50 60Mg (mM)
Kulo Lasi
AcetateFormate
SW-acetateSW-formate
Con
cent
ratio
n(
M)
Figure 4 Mixing lines of formate and acetate versus Mg for the Kulo Lasi fluids Note that the reference deep-sea water sample (FU-PL05-TiG2 noted as SW here) was taken at 1150m depth above the southern wall of the caldera (see Figure 1 for location and Table 3) and thus verylikely within the plume [7] This would account for the unusual concentrations of formate and acetate detected
Geofluids 11
Carla Acetate was detected in all analysed samples andconcentrations were an order of magnitude higher than theones of formate (543ndash2309 ppb) (Table 6)
Heavier extractable organic compounds were notdetected in the dry control experiment and only a few weredetectable but below limit of quantification (LOQ) in theMQ water blank experiment (Table 6) This showed thatsample preparation and storage could be considered ascontamination-free steps The levels of heavier extractableorganic compounds appeared rather high in the referencewater at Fatu Kapa certainly because of the overall spreadhydrothermal discharges and diffuse venting in the region [7](Table 6 Figure 5) This sample was indeed taken mid-waybetween ObelX and AsterX fields at about 20m above theseafloor As a consequence it is difficult to assess possiblecontamination originating from sampling device or seawatercontribution in the present case However earlier studieshave shown that they generally did not represent majorsources of contamination as for the studied compounds[27 37] Nevertheless in comparison to deep-sea waterboth the qualitative (Kulo Lasi) and quantitative (FatuKapa) data obtained suggested enrichment of the fluidsin hydrothermally derived compounds namely n-alkanes(C9ndashC12) n-FAs (C9 C12 C14ndashC18) and PAHs (fluorenephenanthrene pyrene) ([39] Table 6 Figures 5 and 6)Such enrichment was unclear for gtC12 n-alkanes C10C11 C13 n-FAs BTEXs naphthalene acenaphthene andfluoranthene because of their very low concentration andorthe measurement uncertainty
Differences in concentrations seemed to exist among thevents over the Fatu Kapa area Fluids from the Stephanie ventfield had concentrations in hydrocarbons equal or below thereference water sample whereas they were clearly enrichedin C9 C12 C14ndashC18 n-FAs The Carla fluids were slightlyenriched in C9ndashC12 n-alkanes and showed the highest con-centrations in PAHs Fluids from IdefX Fati Ufu and Tutafishared some similarities a strong enrichment in decane andundecane alike concentrations in PAHs and the presence ofsignificant amounts of xylene However fluids expelled at theTutafi vent appeared the most enriched in C9ndashC11 n-alkanesand xylenes In terms of fatty acids and considering theanalytical error the 5 vents showed consistent concentrationswith C9 C16 and C18 being major Note that fluids from FatiUfu seemed depleted in C17 and C18
Generally we did not observe strong linear correlationbetween the concentration of individual compounds andMgNonetheless these relations showed that both enrichmentand depletion of organic compounds seemed to occur inhydrothermal fluids versus deep-sea water
5 Discussion
The elemental and gas composition of hydrothermal fluidsis mainly affected by waterrock interactions and thus thenature of the host rocks phase separation magmatic fluidcontribution conductive cooling and seawater mixing inlocal recharge zones [45] In the following discussion weattempt to unravel the occurrence of these various processes
both at Kulo Lasi and at Fatu Kapa Much less is known onprocesses that control organic geochemistry and are thereforediscussed here as well as some implications of the presenceof organic compounds in hydrothermal fluids Implicationsrelated to the composition of the fluids are dependent onfluxes therefore we give here an attempt to provide order ofmagnitude estimates of heat and mass fluxes
51 Plume-Fluids Relations The geochemistry and dynamicsof the plumes over the Wallis and Futuna region havebeen studied elsewhere [7] The Kulo Lasi plume has beenproposed to be the result of both high-119879 and diffuse ventingfrom multiple vents located both on the floor and on thewall of the caldera Consistently both types of venting havebeen observed [6] Helium nephelometry and Mn profilesrecorded above the northern sampling area showed constantelevated concentrations in the 300masf and were assumedto be the results of diffuse venting Our results show thatthey are obviously the result of the numerous small blacksmokers observed on the seafloor (Figure 2) The methaneconcentration in the sampled fluids was extremely low whichcannot account for the elevated concentration of CH4 inthe water column reported by Konn et al [7] The strongdifference in the CH4Mn ratios between the plume (07ndash45)and the sampled fluids (0001ndash001) is another line of evidencethat the methane plume has another origin compared tohydrothermal fluids and likely come from degassing of thelava flows as suggested by the authors Although other fluiddischarges likely remain undiscovered this is consistent witha past eruption and accumulation of the water mass in thecaldera [39]
A great diversity of the fluid compositions was expectedfrom the geological settings and the water column survey andwas indeed confirmed by the mixing lines that point to asmany endmembers as sampled areas (Figure S1) CH4TDMratios also differed among the vents but it was not due to soleCH4 concentration variations as suggested earlier (Table 5)[7] Finally the very weak nephelometry of the Fatu Kapaplume is likely best explained by the low metal contents ofthe fluids
52 Reaction Zone Depth The solubility of Quartz in hydro-thermal fluids has been studied by different authors (eg[46]) According to these works silica concentration in thefluid may be used to estimate the depth of the reaction zoneThe silica concentration measured in the Kulo Lasi and FatuKapa fluids indicates a hydrothermal reaction zone at seaflooror in thewater column (Figure S2) Both observations suggestthat in this area fluids are not in equilibria with Quartz atthe pressure and temperature of the fluid emission And thisprevents using Si as a geothermometer to determine the depthof the reaction zone
All fluids at Fatu Kapa were indeed highly depleted inSi with respect to the Quartz saturation curve at 170 bar300∘C (Si sim12mM in Figure S2) A higher temperature inthe reaction zone (gt350∘C at 200 bar) may explain a lower Siconcentration in the fluid at equilibrium as Quartz solubilitydecreases (Figure S2) The dispersion of a great number of
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Figure 3 (a) and (b) Photographs of anhydrite structures observed at Stephanie Carla IdefX AsterX and ObelX site (c) Photographs of greysmokers associated with sulphides structures observed at Fati Ufu and Tutafi Copyrights from Ifremer FUTUNA 3 cruise
02468
1012141618
0 10 20 30 40 50 60Mg (mM)
Kulo Lasi
AcetateFormate
SW-acetateSW-formate
Con
cent
ratio
n(
M)
Figure 4 Mixing lines of formate and acetate versus Mg for the Kulo Lasi fluids Note that the reference deep-sea water sample (FU-PL05-TiG2 noted as SW here) was taken at 1150m depth above the southern wall of the caldera (see Figure 1 for location and Table 3) and thus verylikely within the plume [7] This would account for the unusual concentrations of formate and acetate detected
Geofluids 11
Carla Acetate was detected in all analysed samples andconcentrations were an order of magnitude higher than theones of formate (543ndash2309 ppb) (Table 6)
Heavier extractable organic compounds were notdetected in the dry control experiment and only a few weredetectable but below limit of quantification (LOQ) in theMQ water blank experiment (Table 6) This showed thatsample preparation and storage could be considered ascontamination-free steps The levels of heavier extractableorganic compounds appeared rather high in the referencewater at Fatu Kapa certainly because of the overall spreadhydrothermal discharges and diffuse venting in the region [7](Table 6 Figure 5) This sample was indeed taken mid-waybetween ObelX and AsterX fields at about 20m above theseafloor As a consequence it is difficult to assess possiblecontamination originating from sampling device or seawatercontribution in the present case However earlier studieshave shown that they generally did not represent majorsources of contamination as for the studied compounds[27 37] Nevertheless in comparison to deep-sea waterboth the qualitative (Kulo Lasi) and quantitative (FatuKapa) data obtained suggested enrichment of the fluidsin hydrothermally derived compounds namely n-alkanes(C9ndashC12) n-FAs (C9 C12 C14ndashC18) and PAHs (fluorenephenanthrene pyrene) ([39] Table 6 Figures 5 and 6)Such enrichment was unclear for gtC12 n-alkanes C10C11 C13 n-FAs BTEXs naphthalene acenaphthene andfluoranthene because of their very low concentration andorthe measurement uncertainty
Differences in concentrations seemed to exist among thevents over the Fatu Kapa area Fluids from the Stephanie ventfield had concentrations in hydrocarbons equal or below thereference water sample whereas they were clearly enrichedin C9 C12 C14ndashC18 n-FAs The Carla fluids were slightlyenriched in C9ndashC12 n-alkanes and showed the highest con-centrations in PAHs Fluids from IdefX Fati Ufu and Tutafishared some similarities a strong enrichment in decane andundecane alike concentrations in PAHs and the presence ofsignificant amounts of xylene However fluids expelled at theTutafi vent appeared the most enriched in C9ndashC11 n-alkanesand xylenes In terms of fatty acids and considering theanalytical error the 5 vents showed consistent concentrationswith C9 C16 and C18 being major Note that fluids from FatiUfu seemed depleted in C17 and C18
Generally we did not observe strong linear correlationbetween the concentration of individual compounds andMgNonetheless these relations showed that both enrichmentand depletion of organic compounds seemed to occur inhydrothermal fluids versus deep-sea water
5 Discussion
The elemental and gas composition of hydrothermal fluidsis mainly affected by waterrock interactions and thus thenature of the host rocks phase separation magmatic fluidcontribution conductive cooling and seawater mixing inlocal recharge zones [45] In the following discussion weattempt to unravel the occurrence of these various processes
both at Kulo Lasi and at Fatu Kapa Much less is known onprocesses that control organic geochemistry and are thereforediscussed here as well as some implications of the presenceof organic compounds in hydrothermal fluids Implicationsrelated to the composition of the fluids are dependent onfluxes therefore we give here an attempt to provide order ofmagnitude estimates of heat and mass fluxes
51 Plume-Fluids Relations The geochemistry and dynamicsof the plumes over the Wallis and Futuna region havebeen studied elsewhere [7] The Kulo Lasi plume has beenproposed to be the result of both high-119879 and diffuse ventingfrom multiple vents located both on the floor and on thewall of the caldera Consistently both types of venting havebeen observed [6] Helium nephelometry and Mn profilesrecorded above the northern sampling area showed constantelevated concentrations in the 300masf and were assumedto be the results of diffuse venting Our results show thatthey are obviously the result of the numerous small blacksmokers observed on the seafloor (Figure 2) The methaneconcentration in the sampled fluids was extremely low whichcannot account for the elevated concentration of CH4 inthe water column reported by Konn et al [7] The strongdifference in the CH4Mn ratios between the plume (07ndash45)and the sampled fluids (0001ndash001) is another line of evidencethat the methane plume has another origin compared tohydrothermal fluids and likely come from degassing of thelava flows as suggested by the authors Although other fluiddischarges likely remain undiscovered this is consistent witha past eruption and accumulation of the water mass in thecaldera [39]
A great diversity of the fluid compositions was expectedfrom the geological settings and the water column survey andwas indeed confirmed by the mixing lines that point to asmany endmembers as sampled areas (Figure S1) CH4TDMratios also differed among the vents but it was not due to soleCH4 concentration variations as suggested earlier (Table 5)[7] Finally the very weak nephelometry of the Fatu Kapaplume is likely best explained by the low metal contents ofthe fluids
52 Reaction Zone Depth The solubility of Quartz in hydro-thermal fluids has been studied by different authors (eg[46]) According to these works silica concentration in thefluid may be used to estimate the depth of the reaction zoneThe silica concentration measured in the Kulo Lasi and FatuKapa fluids indicates a hydrothermal reaction zone at seaflooror in thewater column (Figure S2) Both observations suggestthat in this area fluids are not in equilibria with Quartz atthe pressure and temperature of the fluid emission And thisprevents using Si as a geothermometer to determine the depthof the reaction zone
All fluids at Fatu Kapa were indeed highly depleted inSi with respect to the Quartz saturation curve at 170 bar300∘C (Si sim12mM in Figure S2) A higher temperature inthe reaction zone (gt350∘C at 200 bar) may explain a lower Siconcentration in the fluid at equilibrium as Quartz solubilitydecreases (Figure S2) The dispersion of a great number of
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Carla Acetate was detected in all analysed samples andconcentrations were an order of magnitude higher than theones of formate (543ndash2309 ppb) (Table 6)
Heavier extractable organic compounds were notdetected in the dry control experiment and only a few weredetectable but below limit of quantification (LOQ) in theMQ water blank experiment (Table 6) This showed thatsample preparation and storage could be considered ascontamination-free steps The levels of heavier extractableorganic compounds appeared rather high in the referencewater at Fatu Kapa certainly because of the overall spreadhydrothermal discharges and diffuse venting in the region [7](Table 6 Figure 5) This sample was indeed taken mid-waybetween ObelX and AsterX fields at about 20m above theseafloor As a consequence it is difficult to assess possiblecontamination originating from sampling device or seawatercontribution in the present case However earlier studieshave shown that they generally did not represent majorsources of contamination as for the studied compounds[27 37] Nevertheless in comparison to deep-sea waterboth the qualitative (Kulo Lasi) and quantitative (FatuKapa) data obtained suggested enrichment of the fluidsin hydrothermally derived compounds namely n-alkanes(C9ndashC12) n-FAs (C9 C12 C14ndashC18) and PAHs (fluorenephenanthrene pyrene) ([39] Table 6 Figures 5 and 6)Such enrichment was unclear for gtC12 n-alkanes C10C11 C13 n-FAs BTEXs naphthalene acenaphthene andfluoranthene because of their very low concentration andorthe measurement uncertainty
Differences in concentrations seemed to exist among thevents over the Fatu Kapa area Fluids from the Stephanie ventfield had concentrations in hydrocarbons equal or below thereference water sample whereas they were clearly enrichedin C9 C12 C14ndashC18 n-FAs The Carla fluids were slightlyenriched in C9ndashC12 n-alkanes and showed the highest con-centrations in PAHs Fluids from IdefX Fati Ufu and Tutafishared some similarities a strong enrichment in decane andundecane alike concentrations in PAHs and the presence ofsignificant amounts of xylene However fluids expelled at theTutafi vent appeared the most enriched in C9ndashC11 n-alkanesand xylenes In terms of fatty acids and considering theanalytical error the 5 vents showed consistent concentrationswith C9 C16 and C18 being major Note that fluids from FatiUfu seemed depleted in C17 and C18
Generally we did not observe strong linear correlationbetween the concentration of individual compounds andMgNonetheless these relations showed that both enrichmentand depletion of organic compounds seemed to occur inhydrothermal fluids versus deep-sea water
5 Discussion
The elemental and gas composition of hydrothermal fluidsis mainly affected by waterrock interactions and thus thenature of the host rocks phase separation magmatic fluidcontribution conductive cooling and seawater mixing inlocal recharge zones [45] In the following discussion weattempt to unravel the occurrence of these various processes
both at Kulo Lasi and at Fatu Kapa Much less is known onprocesses that control organic geochemistry and are thereforediscussed here as well as some implications of the presenceof organic compounds in hydrothermal fluids Implicationsrelated to the composition of the fluids are dependent onfluxes therefore we give here an attempt to provide order ofmagnitude estimates of heat and mass fluxes
51 Plume-Fluids Relations The geochemistry and dynamicsof the plumes over the Wallis and Futuna region havebeen studied elsewhere [7] The Kulo Lasi plume has beenproposed to be the result of both high-119879 and diffuse ventingfrom multiple vents located both on the floor and on thewall of the caldera Consistently both types of venting havebeen observed [6] Helium nephelometry and Mn profilesrecorded above the northern sampling area showed constantelevated concentrations in the 300masf and were assumedto be the results of diffuse venting Our results show thatthey are obviously the result of the numerous small blacksmokers observed on the seafloor (Figure 2) The methaneconcentration in the sampled fluids was extremely low whichcannot account for the elevated concentration of CH4 inthe water column reported by Konn et al [7] The strongdifference in the CH4Mn ratios between the plume (07ndash45)and the sampled fluids (0001ndash001) is another line of evidencethat the methane plume has another origin compared tohydrothermal fluids and likely come from degassing of thelava flows as suggested by the authors Although other fluiddischarges likely remain undiscovered this is consistent witha past eruption and accumulation of the water mass in thecaldera [39]
A great diversity of the fluid compositions was expectedfrom the geological settings and the water column survey andwas indeed confirmed by the mixing lines that point to asmany endmembers as sampled areas (Figure S1) CH4TDMratios also differed among the vents but it was not due to soleCH4 concentration variations as suggested earlier (Table 5)[7] Finally the very weak nephelometry of the Fatu Kapaplume is likely best explained by the low metal contents ofthe fluids
52 Reaction Zone Depth The solubility of Quartz in hydro-thermal fluids has been studied by different authors (eg[46]) According to these works silica concentration in thefluid may be used to estimate the depth of the reaction zoneThe silica concentration measured in the Kulo Lasi and FatuKapa fluids indicates a hydrothermal reaction zone at seaflooror in thewater column (Figure S2) Both observations suggestthat in this area fluids are not in equilibria with Quartz atthe pressure and temperature of the fluid emission And thisprevents using Si as a geothermometer to determine the depthof the reaction zone
All fluids at Fatu Kapa were indeed highly depleted inSi with respect to the Quartz saturation curve at 170 bar300∘C (Si sim12mM in Figure S2) A higher temperature inthe reaction zone (gt350∘C at 200 bar) may explain a lower Siconcentration in the fluid at equilibrium as Quartz solubilitydecreases (Figure S2) The dispersion of a great number of
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Figure 5 Distribution of n-alkanes n-fatty acids mono- and polyaromatic hydrocarbons (BTEX and PAH) in the purest fluids of theStephanie Carla IdefX Fati Ufu and Tutafi sites collected within the Fatu Kapa vent field Because organic geochemistry does not seem tofollow a simple mixing model endmember concentrations cannot be calculated To that respect composition of the purest fluids is presentedand assumed to be close to endmembers composition Note that quantitative results are not available for the Kulo Lasi fluids (see Figure 6 forchromatograms)
Geofluids 15
0200000
1000000
2000000
3000000
4000000
5000000
Abu
ndan
ce
4 181614121086
123 1271261251240
100000
500000
900000
Dodecanoicacid
58 6059 61 62
Decane
0
100000
200000
83 878685840
100000
200000 Dodecane
103 106105104
Decanoic acid
0
100000
200000
88
(min)
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Figure 6 Only qualitative results could be obtained at Kulo Lasi This figure presents a selection of representative chromatograms obtainedfor the Kulo Lasi fluid samples For the sake of clarity close-ups of a few peaks are shown to illustrate the enrichment of fluids (FU-PL06-TiG1in red and FU-PL06-TiD3 in green) versus the reference deep-sea water (FU-PL05-TiG2 in blue)
vent fields over a large area of recent lava flows may be dueto complex fluid pathways that favour conductive cooling ofthe fluid and subsurface loss of silica before venting on theseafloor Consistently amorphous silica was common in theseafloor deposits at Fatu Kapa where opal was abundant asa late mineral in sulphides and as silica crusts (slabs) at thesurface of the deposits [6] In conclusion this would indicatea fairly shallow reaction zone at Fatu Kapa (a few 100mbsf)in agreement with the geological settings and the possibleoccurrence of dikes
53 Chlorinity Phase separation is often accounted for salin-ity deviation in hydrothermal fluids versus seawater [47 48]Phase separation is of great importance in metal transporta-tion and ore-forming processes for example [24 49ndash51]It also implies that seawater experiences dramatic changesin its physical and chemical properties as it reaches thesuper- or subcritical state In particular strong modificationof the density and ionic strength of seawater enables uncon-ventional chemical reactions hence a likely importance inhydrothermal organic geochemistry for example [52] Themeasured 119875 and 119879 of the Kulo Lasi fluids are almost on the
critical curve of seawatermeaning that liquid and vapor phasemay coexist at Kulo Lasi An adiabatic decompression ofsupercritical seawater (initial fluid and equivalent to 32 wtNaCl) as it rises towards the seafloor would cause it toseparate at about 320ndash350 bar and 415ndash420∘C into twophases having the NaCl percentages observed at Kulo Lasi(Figure S3) [53 54]
Similarly the excess salinity of the Fatu Kapa fluids (9 to41) could be explained by phase separation and is supportedby the BrCl ratios which significantly differed from seawater[45 55] Since we have not sampled any Cl-depleted fluidswe may infer that phase separation may have occurred inthe past and that only the brine phase was venting at thetime of the cruise Alternatively water-rock reactions couldrepresent a significant Cl source to the fluids [56] Indeedthe felsic lavas collected in the Fatu Kapa area contained upto 10 timesmore Cl thanMORB (Aurelien Jeanvoine personalcommunication)
54 Water-Rock Reactions Generally fluids from Kulo Lasiand Fatu Kapa were not typical of back-arc settings butshared similarities with ridge arc and back-arc settings fluid
16 Geofluids
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
signatures [3] The Kulo Lasi fluids have unusually highconcentrations of Mg (246 to 349mM) and SO4 (62 to120mM) at low pH (224 to 332) and high 119879 (338ndash343∘C)which indicate that significant seawater mixing at subsurfaceor during sampling is rather unlikely In back-arc contextthe occurrence of Mg and SO4 in endmember fluids canbe explained by a magmatic fluid input as observed at theDesmos [5 57] Rota 1 and Brother sites [58 59] Magmatic-derived SO2 would disproportionate according to reaction (1)at temperatures measured at Kulo Lasi (eg [5 60]) This isconsistent with widespread occurrences of native sulfur onfresh lava near the active vents [39] as well as the low pH ofthe fluids
3SO2 (aq) + 2H2O = S0 (s) + 4H+ + 2SO4 (1)
Yet CO2 concentrations are low and the Na K Mgratios are strongly different to seawater The latter suggestsa contribution of Mg by dissolution of magnesium silicates[39] Besides the high Li and Rb concentrations and thepresence of recent lava injected in the caldera point towaterfresh hot volcanic rocks interactions Notably suchinteractions are capable of producing the extremely highconcentration of H2 measured in the Cl-depleted sample andthus the very unusual H2CH4 observed [61] (Figure S4)High concentrations of metals are consistent with the highlyacidic nature of the fluids coupled with high H2H2S ratios[62 63]
The relatively mild pH 3HeCO2 and RRa ratios of theFatu Kapa fluids are diagnostic of the occurrence of seawa-terMORB interactions [64ndash66] (Figure S5) Consistently thegeochemistry of the Fatu Kapa fluids was very similar to theVienna Woods ones whose composition is mainly the resultof interactions with basalts [3 4] Yet metal concentrationswere lower at Fatu Kapa while Ca K and Rb were higherand Li is similar Plausible explanations for the extremelylow metal concentrations observed in the Fatu Kapa fluidsare conductive cooling watermetal-poor rocks interactionssubsurface metal trapping under silica and barite slabs [6]Given the wide variety of lithologies sampled in the areafluid compositions are likely the results of interactions witha wide range of rock source chemistries To that respectthe composition of the local lavas that are characteristic ofandesite trachy-andesite dacite and trachy-dacite probablybest explains the enrichment in Ca and in the mobile alkalimetals K and Rb
55 What Controls Organic Geochemistry The origin ofhydrocarbon gases and SVOCs in natural systems includinghydrothermal systems has been the focus of many studiessince the abiotic origin of some hydrocarbons was postulated([67 68] for a review) Both field and experimental studieshave tried to unravel the origin of hydrocarbons making useof stable isotopes (eg reviews of [34 35]) Although thereare strong discrepancies among studies the variation of 12057513Cwith the carbon number may be a reasonable indicator ofthe origin The trend observed in the Cl-depleted sampleof Kulo Lasi was very similar to the ones attributed to anabiogenic origin in the Precambrian shields or in the Lost
City hydrothermal field [69 70]TheKulo Lasi Cl-rich sampleexhibited a pattern that has been observed in several Fischer-Tropsch type (FTT) experiments [34] The strong positive ornegative fractionation between C1 and C2 observed in thehot fluids of Kulo Lasi is likely due to chain initiation [71]Conversely the low-119879 (135∘C) sample that was collected ina beehive-type smoker covered with bacterial mats showeda regular positive trend which has been proposed to bediagnostic of a thermogenic origin Althoughwe concede thatthe abiogenic origin of C2+ hydrocarbon gases in the KuloLasi field will need more investigation methane is clearly atthe border of abiogenic and thermogenic domains both atKulo Lasi and at Fatu Kapa with 12057513C values ranging fromminus29 to minus61permil ([72] and Figure 7) Carbon isotopes of CH4andCO2 suggest thatmethane underwent oxidation possiblyby bacteria at both sites and may explain the extremely lowconcentrations observed (Figure 8 in [73]) Consistently andaccording to thermodynamic calculations methanogenesisshould be limited under the 119875 119879 and redox conditionspresent at the Futuna sites and CH4 consumption might beprevalent [31]
By contrast carbon isotopes have not appeared to beuseful up to date in determining the origin of heavierorganic compounds [74] Several processes are likely to occursimultaneously and to use several C sources resulting ina nondiagnostic bulk 12057513C signature Several experimentaland theoretical studies indicate that a range of organiccompounds including linear alkanes and FAs could formand persist in natural hydrothermal systems (eg [31ndash35])However according to the calculated 119891H2 at 119875 and 119879 ofthe study sites the redox conditions are likely buffered byHematite-Magnetite (HM) or an even more oxidizing min-eral assemblage which appear less favourable for abiotic syn-thesis than Pyrite-Pyrrhotite-Magnetite Fayalite-Magnetite-Quartz or ultramafic rocks assemblages [27 32 33] (Table 4)The occurrence of organic compounds in our fluidsmust thusbe attributed to a great part to other processes Microbialproduction and thermal degradation ofmicroorganisms OMdetritus andor refractory dissolved OM represent goodcandidates to produce soluble organic compounds PAHs areindeed common products of pyrolysis of OM [26 75 76]Long chained fatty acids are major constituent of organismsand their presence in the Futuna fluids could be easilyassociated with thermal degradation of biomass or OM [2677] Yet the distribution of the compounds found in the fluidsdoes not match a simple process of OM degradation OnlygtC13 n-FAs occurred in sediments with C16 being the mostabundant (Figure S6) However similar to our samples bothodd and even carbon number n-FAs were observed in theC14ndashC20 range with odd FAs being less abundant Petroleumexhibits nearly equal levels of C14ndashC20 n-FAs Only the evenseries has been reported in both massive sulphide deposits(MSD) and hydrothermal mussels with C16 being the mostabundant Short chain FAs (ltC13) have only been reported inLost City fluids but here again only the even series occurredIn any case C9 was reported whereas it was nearly themost abundant in our fluids Abiotic processes may still beconsidered as nonanoic acid could be synthesized from CO2
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
Figure 7 Modified after Etiope and Sherwood Lollar [9] The isotopic composition of CH4 in the Fatu Kapa fluids falls into the abiotic gascategory but differs from the typical isotopic signature of CH4 at Mid-Atlantic Ridgersquos vent fields
and H2 [31] nonane [78] or undecane [79] As a differencethe presence of C16 and C18 n-FAs in significant amount inthe fluids from Fatu Kapa may represent a direct microbialcontribution The distribution observed in the Fatu Kapafluids likely reflects the occurrence of several concomitantprocesses possibly including production reactions (abioticand thermogenic) and consumption mechanisms (adsorp-tion and complexation)
Nonvolatile n-alkanes are usually associated with lower119879 processes such as in oil fields or at the Middle Valleyhydrothermal vent field [80] In the Guaymas basin wheren-alkane-rich sediment samples have been reported it isless clear what temperature they were exposed to Howeverand as far as we understood high temperatures were ratherassociated with absence of n-alkanes and presence of PAHsconsistently with high-temperature OMpyrolysis [26 81 82]Pyrolytic processes resulted in the presence of light hydrocar-bon gases with an exception of some high 119879 (gt200∘C) fluidscontaining C9 and C10 n-alkanes n-Alkanes also occur insolids from unsedimented hydrothermal vent fields ([76] andreferences therein) Notably the n-alkanes distribution in ourfluids does not resemble any aspects neither the ones resultingof low-119879 processes nor the ones created by high-119879 FTT reac-tions [83 84] (Figure S7) C10ndashC20 n-alkanes usually occurin equivalent amounts in petroleum or show a consistentdecrease withmolecular weight Experimental FTT reactionsproduced consistent increasing concentrations from C9 toC12 and then consistent decreasing concentrations to C20Similar patterns are also associatedwith the kerosene fractionof petroleum [85] Distribution patterns in hydrothermalsolids are difficult to picture as usually only chromatograms
are provided in the studies for example [86] but they largelydiffer by the simple fact that ltC14 alkanes were not detectedin most cases as in sediments from various locations [87]The smaller alkanes may well be preferentially entrained influid circulation but they are more likely the result of otherprocesses especially high-temperature ones and includingabiotic reactions Note that the latter should not be reducedto sole FTT reactions because supercritical water is a fabulousmedium for unconventional reactions [88ndash90]
Formate and acetate have been given more attention inboth laboratory [91ndash93] and field hydrothermal studies [2829] as these small molecules are likely to prevail accordingto thermodynamic studies (eg [31ndash33]) Where usuallyformate dominates acetate was found to be more abundantin fluids from Fatu Kapa According to Shock studies at280ndash300∘C formic acid concentrations should not be muchhigher than acetic acid but this is not enough to explain ourldquoreverserdquo concentrations And especially it is not consistentwith higher amounts in the 300∘C fluids A ratio closeto 1 was observed at Kulo Lasi which may indicate thatdifferent productionconsumption processes occur Also theconcentrations of the formate and acetate plotted on a lineversus Mg which suggest that the fate of these volatile fattyacids at Kulo Lasi is controlled by simple mixing that is therewould be no consumptionproduction when fluidmixes withseawater (Figure 4) The deep-seawater concentrations werehigh compared to what is usually reported in the literaturewhich was most likely due to plume contribution [27 28]This supports the simple mixing model hypothesis and isconsistent with the near absence of organisms around thosechimneys
18 Geofluids
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
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[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
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[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
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[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
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[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
56 Organic Compounds Implications for Biology MineralResources and C Cycling The idea that life could haveoriginated in hydrothermal systems from abiotic reactionswas postulated in the late 70s [94] However the questionof the origin of organic compounds in hydrothermal systemshas remained ever since they were evidenced in natural envi-ronments [95] On the one hand a biogenic or thermogenicorigin seems most likely for most compounds investigated sofar on the other hand one cannot exclude that some of theformate and aliphatic hydrocarbons form abiotically [13 26ndash28 30 96] As detailed in the previous section our resultsare consistent with a mix of origin although abiotic synthesislikely occurs to a far smaller extent than other processes thatwould overprint an abiotic signature
Upon the hot topic of the origin of life the mere presenceof organic compounds is highly important for the fauna atthe local and regional scales It is well established that VFAsconstitute a significant food source for somemicroorganismsand thus help sustaining hydrothermal ecosystems [97ndash100]Besides some bacteria have proven to be capable of usingnaphthalene [101] and tubeworms hydrocarbons [102]
Organics can form complexes with metals [20 21] Thisgreatly improves the dispersion of metals in the ocean andprevents them from precipitation as sulphides or oxyhydrox-ydes [23 103] Notably fatty acids are efficient ligands thatplay a major role in making metals bioavailable as well as intransporting them both through the upper crust ([17] andreferences therein) and through the water column in theplume [11 104ndash106] In addition they have been shown tobe involved in growthdissolution processes of someminerals[19 107] For these reasons they are of particular importancein ore-forming processes Hydrocarbons which are weakerligands would react with sulfates to generate bisulfide (HSminus)which in turn would easily react with metal chlorides toformmetal sulphides according to the followingmass balanceequations
where R is a carbonated chain either aliphatic or aromaticand represents OM [108] To that respect hydrocarbons arelikely to be involved in depositional processes of metalsNotably associations of aliphatic and aromatic hydrocarbonswith mineral deposits have also been observed on the EPR[109] and in sulphide sedimentary deposits on land [104]
57 Fluxes Importance of Back-Arc Hydrothermal Systems tothe Ocean Geochemistry Hydrothermal input to the oceanvia plumes has long been neglected but recent results of theGEOTRACES program clearly show its importance in termsof metals and trace elements transportation and implicationsfor ocean biogeochemistry [13 110ndash113] While it is nowwell established that MOR hydrothermal discharge has alarge impact on the global ocean chemistry and elementcycles the relative impact of hydrothermal activity fromotherhydrothermal settings has not been establishedThe extensive
hydrothermal activity reported in the Wallis and Futunaregion suggests that back-arc system hydrothermalism maybe of much greater importance than previously anticipated[7 114] Estimation of hydrothermal fluxes is generally chal-lenging and very few data are available in the literature [115ndash118] Therefore we believe that any kind of estimation evenorders of magnitudes are of importance to make advances inthis field We propose to combine two different approachesbased on geophysical data and video recordings (see here)respectively to propose such estimates with some confidence
571 Estimation Using Geophysics We can make an orderof magnitude estimate of the heat flux from the differenthydrothermally active areas based on the physical character-istics of the plumes Marshall and coworkers [119ndash121] haveproposed a scaling relationship between the heat flux at aninterface Hf the ambient buoyancy frequency (119873) in thesurroundings of the plume the characteristic size (119877119904) of theheat transfer region and the equilibrium height (or depth ℎ)reached by the plume as
where 120588 is seawater density (1030 kgsdotmminus3)119862119901 is heat capacityof seawater (sim4000 Jsdotkgminus1sdotKminus1) and 119892 is gravitational acceler-ation (981msdotsminus2) and 120572 is the thermal expansion coefficientof seawater (10minus4 Kminus1) The ambient buoyancy frequency (119873)can be estimated to be between 0001 and 0002 sminus1 fromCTDprofiles in the area using a routine in the UNESCO SeaWaterLibrary described by Jackett and Mcdougall [122] The radius(119877119904) of the Kulo Lasi caldera is 2500m and the plume rosein average about 200m above seafloor (top layer boundary)[7] For order of magnitude estimates the sim130 km2 FatuKapa area can be approximated by a disk of radius 6400mwith a similar plume height Introducing these numbers in(4) leads to heat flux estimates ranging between 100 and800Wsdotmminus2 for the Kulo Lasi caldera and 50 and 400Wsdotmminus2for the Fatu Kapa area which is greatly dependent on thevalue for buoyancy frequency While these estimates scaleproportionally with the area considered to be hydrothermallyactive they integrate the sources within the area which do notdemand that the whole area be active We estimate that totalheat inputs are in the 2ndash16GW for the Kulo Lasi caldera and5ndash40GW for the Fatu Kapa areas
572 Estimation Based on Video Postprocessing Video re-cordings could be used to estimate fluid velocities of theCarla and ObelX chimneys and of a few smokers at KuloLasi using for instance the Typhoon algorithm [123] (FiguresS8ndashS11) This optical flow method recovers the (2D) fluidflow from the apparent displacements in an image sequenceof tracers advected by the flow Here the plume acts as thetracer Compensation for the camera and vehicle motionand parallax correction were not possible so the investigatedvideo sequences where chosen according to (i) the overallstability of the camera and vehicle and (ii) the plume beingas perpendicular to the camera as possible The relevant
Geofluids 19
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
lengths scales (image spatial resolution and diameter of thechimneys) had to be estimated from known object sizes inthe same ground typically shrimps External diameters ofthe chimney were used for calculation as any estimationof the internal diameter on video recordings would be toospeculative Note that (i) chimney samples taken at KuloLasi exhibited similar internal and external diameters (ii) thelarge anhydrite chimneys (eg ObelX Carla) at Fatu Kapadid not seem to have any central conduit but rather exhibiteda sponge-like structure leaking fluid at a high velocity fromthe entire volume As a result we believe the overestimationresulting from this assumption to be limited Finally theobserved flow velocity is assumed to be constant across thejet section Given all these limitations and assumptions theresulting fluxes values should be taken as an indication oftheir order of magnitude
The fluid velocity was estimated to be on average 005015 and 1m sminus1 for Kulo Lasi Carla and ObelX respectivelyIn terms of heat fluxes Carla (diameter ca 70 cm) wouldgenerate sim6MW while ObelX (diameter ca 250 cm) wouldproduce sim57GW respectively Associated mass fluxes wouldbe 54 L sminus1 and 5m3 sminus1 which means for instance thatthe single ObelX chimney could generate an input of 26times 107mol yminus1 CH4 to the ocean Comparatively estimationof the total efflux of methane from serpentinisation rangesfrom 15 to 84 times 109mol yminus1 including 9 times 109mol yminus1 forthe sole slow spreading ridges Similarly the Carla chimneywould release about 57 times 103mol yminus1 of dodecane that mayhelp forming 14mol yminus1 of metal sulphides (see Section 56)Cumulative observations during the dives brought to a totalof 220 smokers of various sizes (sim5 cm to sim25m in diameter)and apparent flows (strong medium slow) We assigned thestrong medium and slow flows observed to the velocitiesof ObelX Carla and Kulo Lasi respectively At Kulo Lasiabout 100 smokers were counted during the Nautile divesand all appeared very similar in diameter (sim3 cm) and fluidflow (005) Keeping in mind these uncertainties an orderof magnitude of the heat and mass fluxes generated by hotsmokers at FatuKapa are estimated to be 68GWand 6m3 sminus1for the Fatu Kapa area versus 9MW and 6 L sminus1 for theKulo Lasi caldera This means for example that the totalFe flux from hot fluids emanating from the caldera wouldbe up to 19 times 106mol yminus1 versus recent estimations of theglobal hydrothermal iron input that are about 109mol yminus1[112 124] The average nonanoic acid concentration in FatuKapa purest fluids is 725 ppb which would result in 14times 106mol yminus1 released in the ocean by the Fatu Kapa hotsmokers The carboxylic acid functional group of fatty acidsmakes them good potential ligands to form coordinationcomplexes with iron which stabilises iron in the plume inits reduced form [103 125] Hence the example of nonanoicacid suggests that fatty acids could largely contribute to ironstabilisation
However the high-temperature fluxes calculated abovefailed to include heat fluxes from diffusive venting whichwas largely present in both areas and is thought to be animportant part of the global hydrothermal heat flux (up to98) [126]The surface of the diffusive areas was also assessed
on the videos However because the velocity of diffusivefluids could not be estimated using Typhoon we assumedhydrothermal waters are exiting the seafloor at the minimumvelocity reported for low temperature flow (004m sminus1) [127]The cumulative surface of diffusive areas with a typicaltemperature of 10∘C reached 100m2 at Kulo Lasi and 2885m2at Fatu Kapa In addition a particular area of about 300m2 atKulo Lasi consisted in hundreds of silica chimney diffusing a40∘C fluid [6] The resulting contribution of diffuse ventingto the heat flux would be 214GW and 53GW at KuloLasi and Fatu Kapa respectively This brings the total heatflux estimates at 215 GW and 12GW respectively which isconsistent with the estimates obtained using the lower 119873value as well as the fact that only a small portion of the totalsurface of the sites was explored with the submersible
573 Summary According to these different estimates heatefflux at Kulo Lasi and FatuKapa are conservatively estimatedto be at least for 1-2GW and 5ndash10GW respectively thisestimate is based on the low 119873 value whereas using thehigher 119873 suggests a flux almost 10x higher It seems highlylikely that the Wallis and Futuna active areas combinedwith the 3 calderas to the East [114] have a heat flux ofgt10GW Vent fields on MOR have been reported to generatebetween 10MWand 25GW([116 117 127 128] and referencestherein) and the total hydrothermal heat flux at MORs isestimated to be about 1000GW [129 130] This suggeststhat the presently discovered area might be of significantimportance in the global budget and that back-arc hydrother-mal activity contributes as much as MOR systems andpossibly more to the global ocean chemistry and cyclesFew estimates of hydrothermal heat flux have been publishedand the relative importance of heat fluid and geochemicalhydrothermal fluxes from different environments will requirestudies designed to more accurately gauge these fluxes
6 Concluding Remarks
The study of the geochemical characteristics of hydrother-mal fluids from the Wallis and Futuna area confirmed thegreat potential of the region to generate a variety of fluidchemistries as it was expected considering its particular geo-logical context This supports the idea that the hydrothermalcontribution of back-arc environments is of great interest forthe global ocean chemistryOur order ofmagnitude estimatesof fluxes suggest that back-arc hydrothermal activity con-tributes asmuch asMOR systems and possiblymore Notablythe sole ObelX chimney could generate sim1permil of the totalhydrothermally derived CH4 The diversity observed in theWallis and Futuna area also emphasizes that each new fieldpresents its own characteristics and that exploration shouldcontinue A huge number of sites remain to be discoveredaccording to the newly published estimation of vent fieldsoccurring on Earth [131]
A special focus was brought on organic geochemistrybecause of the few data available in modern hydrothermalsystems despite the recent growing interest for oceanic OMConcentrations of SVOCs are the first to be reported which
20 Geofluids
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
will have implications in a wide range of questions andfields Our results are relevant to the understanding of Ccycling and complete the works by Hawkes and Rossel whodemonstrated that DOM is recycled if not removed partiallythrough hydrothermal systems but who could not identifycompounds in DOM Identification of organic moleculesis especially needed to better understand organometallicchemistry at hydrothermal vents and thus utilisation bymicrobes metal export and ore-forming processes The dis-tribution patterns obtained revealed the occurrence of severalprocesses controlling organic geochemistry and notably thatone cannot exclude abiotic synthesis to occur in the study areabut very likely to a so small extent that the signature would beoverprinted
This brings the idea that using natural concentrationsto feed thermodynamic models of abiotic synthesis andorguide the design of experimental work should enable makingprogress in unravelling the origin of organic compounds inhydrothermal systems In addition growing techniques asclumped isotopes [132] and position specific isotopes mea-surements [133] are available and should also help answeringthis question
Conflicts of Interest
The authors declare that they have no conflicts of interest
Acknowledgments
The 2010 and 2012 cruises to the French EEZ of Wallis andFutuna were financed through a publicprivate consortium ofthe French state Ifremer AAMP and BRGM and industrialgroups including Eramet Technip and Areva The authorsare very grateful to the ship crew and the ship captains JRGlehen P Moimeaux and R Picard for running these threecruises with skills and professionalismThey acknowledge allthe scientific parties of these cruises for their collaborationThey are also grateful to D Pierre C Guerin and ANormand for processing bathymetric data on board andthank A-S Alix for providing the final maps They areindebted to the physical oceanographers L Marie and B LeCannwho helped a lot with fluxes estimations andwatermassphysics Finally many thanks are due to P Derian from theFluminance team (Inria Rennes France) who postprocessedvideo recordings usingThyphoon for fluxes estimation
Supplementary Materials
Supplementary 1 S1 mixing lines used for calculation ofthe endmember composition of the Fatu Kapa fluids S2modified after Von Damm et al [46] Plot of the molality ofdissolved SiO2 in equilibrium with quartz in seawater versustemperature for isobars from 1500 to 1000 bar according toVon Damm et al model The Si most enriched fluid collectedat Kulo Lasi is represented by the blue star The red circlecovers the range of Si concentrations and 119879 encounteredin fluids from the Fatu Kapa vent field S3 modified afterBischoff and Pitzer [53] Stars stand for Kulo Lasi fluid phasescharacteristics They nearly plot on the 150-bar isobar The
close-up of the 400∘C 300-bar region shows that seawatercould produce the observed salinities at Kulo Lasi by phaseseparation at about 320ndash350 bar and 415ndash420∘C S4 modifiedafter Kawagucci et al [134] Plots of H2 concentrationversus CH4 concentration in various hydrothermal fluidsThe grey area represents values observed in a hydrothermalexperiment using natural seafloor sediments Values obtainedfor the Wallis and Futuna vent fields are reported KuloLasi brine and condensed vapour phases are marked by thered square and the blue diamond respectively and the blueshaded area covers the range of values obtained in the FatuKapa field S5 modified after Lupton et al [66] (a) Plotsummarizing 3He4He ratio versus C3He for various mantleprovinces includingmid-ocean ridges (black-filled symbols)submarine arc volcanoes (blue) and sub aerial arc volcanoes(green) Values for the Fatu Kapa vent field are reported asorange diamonds 3He4He is expressed as RRa Crossesindicate average values for MORBs and for subaerial arcsfrom (b) Similar plot including values for hotspot volcanoessuch as Loihi Kilauea fumarole Yellowstone Park gasesReunion and Fatu Kapa (orange diamonds) S6 distributionof linear fatty acids in various environments Data are from[135] for Massive Sulphide Deposits (MSD) [36] for LostCity (LC) fluids [136] for petroleum and recent and ancientsediments [137] for 13∘N mussels S7 distribution of linearalkanes obtained by thermogenicmaturation in various crudeoil basins and abiotic Fischer-Tropsch type experiment [84]S11 time series of the estimated displacements correspondingto the video sequences shown in Figures S8 S9 and S10Supplementary 2 S8 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) on one of the small black smokers in the Kulo LasicalderaSupplementary 3 S9 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the base of the Carla chimneySupplementary 4 S10 example of a postprocessed videosequence using the Typhoon algorithm to estimate displace-ments (instantaneous left panel averaged on 25 frames rightpanel) at the top of the massive ObelX chimney S11 timeseries of the estimated displacements corresponding to thevideo sequences shown in Figures S8 S9 and S10
References
[1] S E Beaulieu ldquoInterRidge Global Database of Active Sub-marine Hydrothermal Vent Fields prepared for InterRidgeVersion 33rdquo World Wide Web electronic publication Version34 2015
[2] Y Fouquet U Vonstackelberg J L Charlou et al ldquoHydrother-mal activity in the Lau back-arc basinSulfides and waterchemistryrdquo Geology vol 19 pp 303ndash306 1991
[3] MDHannington C D J de Ronde and S Petersen ldquoSea-floortectonics and submarine hydrothermal systemsrdquo in EconomicGeology 100th Anniversary Volume Society of Economic Geolo-gists J W Hedenquist J F H Thompson R J Goldfarb and
Geofluids 21
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
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[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
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[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
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[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
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[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
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[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
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[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
J P Richards Eds pp 111ndash141 Society of Economic GeologistsLittelton Colorado USA 2005
[4] E P Reeves J S Seewald P Saccocia et al ldquoGeochemistry ofhydrothermal fluids from the PACMANUSNortheast Pual andVienna Woods hydrothermal fields Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 75 no 4 pp1088ndash1123 2011
[5] J S Seewald E P Reeves W Bach et al ldquoSubmarine ventingof magmatic volatiles in the Eastern Manus Basin Papua NewGuineardquo Geochimica et Cosmochimica Acta vol 163 pp 178ndash199 2015
[6] Y Fouquet A S Alix D Birot et al ldquoDiscovery of ExtensiveHydrothermal Fields in the Wallis and Futuna Back-Arc Envi-ronment (SW Pacific)rdquo in Proceedings of the SGA - 13th BiennialMeeting - Mineral Resources in a Sustainable World SGA Edpp 1223ndash1226 Nancy France 2015
[7] C Konn E Fourre P Jean-Baptiste et al ldquoExtensive hydrother-mal activity revealed by multi-tracer survey in the Wallisand Futuna region (SW Pacific)rdquo Deep-Sea Research Part IOceanographic Research Papers vol 116 pp 127ndash144 2016
[8] M Bevis FW Taylor B E Schutz et al ldquoGeodetic observationsof very rapid convergence and back-arc extension at the tongaarcrdquo Nature vol 374 no 6519 pp 249ndash251 1995
[9] G Etiope and B Sherwood Lollar ldquoAbiotic methane on earthrdquoReviews of Geophysics vol 51 no 2 pp 276ndash299 2013
[10] R M W Amon ldquoCarbon cycle Ocean dissolved organicsmatterrdquo Nature Geoscience vol 9 no 12 pp 864-865 2016
[11] S A Bennett P J Statham D R H Green et al ldquoDissolvedand particulate organic carbon in hydrothermal plumes fromthe East Pacific Rise 9∘50rsquoNrdquoDeep-Sea Research Part I Oceano-graphic Research Papers vol 58 no 9 pp 922ndash931 2011
[12] J A Hawkes C T Hansen T Goldhammer W Bach and TDittmar ldquoMolecular alteration ofmarine dissolved organicmat-ter under experimental hydrothermal conditionsrdquo Geochimicaet Cosmochimica Acta vol 175 pp 68ndash85 2016
[13] J A Hawkes P E Rossel A Stubbins et al ldquoEfficient removalof recalcitrant deep-ocean dissolved organic matter duringhydrothermal circulationrdquo Nature Geoscience vol 8 no 11 pp856ndash860 2015
[14] S Q Lang D A Butterfield M D Lilley H Paul Johnsonand J I Hedges ldquoDissolved organic carbon in ridge-axis andridge-flank hydrothermal systemsrdquo Geochimica et Cosmochim-ica Acta vol 70 no 15 pp 3830ndash3842 2006
[15] K Longnecker ldquoDissolved organic matter in newly formed seaice and surface seawaterrdquoGeochimica et CosmochimicaActa vol171 pp 39ndash49 2015
[16] J A Breier BMToner S C Fakra et al ldquoSulfur sulfides oxidesand organic matter aggregated in submarine hydrothermalplumes at 9∘50rsquoN East Pacific Riserdquo Geochimica et Cosmochim-ica Acta vol 88 pp 216ndash236 2012
[17] J Brugger W Liu B Etschmann Y Mei D M Shermanand D Testemale ldquoA review of the coordination chemistry ofhydrothermal systems or do coordination changes make oredepositsrdquo Chemical Geology vol 447 pp 219ndash253 2016
[18] J N Fitzsimmons S G John C M Marsay et al ldquoIron persis-tence in a distal hydrothermal plume supported by dissolved-particulate exchangerdquo Nature Geoscience vol 10 no 3 pp 195ndash201 2017
[19] Q Gautier U-N Berninger J Schott and G Jordan ldquoInfluenceof organic ligands onmagnesite growth Ahydrothermal atomicforce microscopy studyrdquoGeochimica et Cosmochimica Acta vol155 pp 68ndash85 2015
[20] L J A Gerringa M J A Rijkenberg V Schoemann P Laanand H J W de Baar ldquoOrganic complexation of iron in theWestAtlantic OceanrdquoMarine Chemistry vol 177 pp 434ndash446 2015
[21] J A Hawkes D P Connelly M Gledhill and E P AchterbergldquoThe stabilisation and transportation of dissolved iron fromhigh temperature hydrothermal vent systemsrdquo Earth and Plan-etary Science Letters vol 375 pp 280ndash290 2013
[22] W B Homoky ldquoBiogeochemistry Deep ocean iron balancerdquoNature Geoscience vol 10 no 3 pp 162ndash164 2017
[23] S G Sander and A Koschinsky ldquoMetal flux from hydrothermalvents increased by organic complexationrdquo Nature Geosciencevol 4 no 3 pp 145ndash150 2011
[24] T M Seward A E Williams-Jones and A A Migdisov ldquoTheChemistry of Metal Transport and Deposition by Ore-FormingHydrothermal Fluids A2rdquo in Treatise on Geochemistry H DHolland and K K Turekian Eds pp 29ndash57 Elsevier OxfordEngland 2nd edition 2014
[25] B M Toner S C Fakra S J Manganini et al ldquoPreservationof iron(II) by carbon-rich matrices in a hydrothermal plumerdquoNature Geoscience vol 2 no 3 pp 197ndash201 2009
[26] C Konn D Testemale J Querellou N G Holm and J LCharlou ldquoNew insight into the contributions of thermogenicprocesses and biogenic sources to the generation of organiccompounds in hydrothermal fluidsrdquoGeobiology vol 9 no 1 pp79ndash93 2011
[27] C Konn J L Charlou J P Donval N G Holm F Dehairs andS Bouillon ldquoHydrocarbons and oxidized organic compoundsin hydrothermal fluids from Rainbow and Lost City ultramafic-hosted ventsrdquo Chemical Geology vol 258 no 3-4 pp 299ndash3142009
[28] S Q Lang D A Butterfield M Schulte D S Kelley andM D Lilley ldquoElevated concentrations of formate acetate anddissolved organic carbon found at the Lost City hydrothermalfieldrdquo Geochimica et Cosmochimica Acta vol 74 no 3 pp 941ndash952 2010
[29] J M McDermott J S Seewald C R German and S PSylva ldquoPathways for abiotic organic synthesis at submarinehydrothermal fieldsrdquo Proceedings of the National Acadamy ofSciences of theUnited States of America vol 112 no 25 pp 7668ndash7672 2015
[30] E P Reeves J M McDermott and J S Seewald ldquoThe origin ofmethanethiol in midocean ridge hydrothermal fluidsrdquo Proceed-ings of the National Acadamy of Sciences of the United States ofAmerica vol 111 no 15 pp 5474ndash5479 2014
[31] E Shock and P Canovas ldquoThe potential for abiotic organicsynthesis and biosynthesis at seafloor hydrothermal systemsrdquo inGEOFLUIDS pp 161ndash192 Blackwell Publishing Ltd HobokenNew Jersey USA 2010
[32] E L Shock ldquoGeochemical constraints on the origin of organiccompounds in hydrothermal systemsrdquo Origins of Life andEvolution of Biospheres vol 20 no 3-4 pp 331ndash367 1990
[33] E L Shock ldquoChapter 5 Chemical environments of submarinehydrothermal systemsrdquo Origins of Life and Evolution of Bio-spheres vol 22 no 1-4 pp 67ndash107 1992
[34] T M McCollom ldquoLaboratory simulations of abiotic hydrocar-bon formation in earthrsquos deep subsurfacerdquo Reviews in Mineral-ogy and Geochemistry vol 75 pp 467ndash494 2013
[35] T M McCollom and J S Seewald ldquoAbiotic synthesis of organiccompounds in deep-sea hydrothermal environmentsrdquoChemicalReviews vol 107 no 2 pp 382ndash401 2007
22 Geofluids
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
[36] TMMcCollom J S Seewald andC RGerman ldquoInvestigationof extractable organic compounds in deep-sea hydrothermalvent fluids along the Mid-Atlantic Ridgerdquo Geochimica et Cos-mochimica Acta vol 156 pp 122ndash144 2015
[37] C Konn J-L Charlou J-P Donval and N G Holm ldquoChar-acterisation of dissolved organic compounds in hydrothermalfluids by stir bar sorptive extraction - gas chomatography -mass spectrometry Case study The Rainbow field (36∘N Mid-Atlantic Ridge)rdquo Geochemical Transactions vol 13 article no 82012
[38] B Pelletier Y Lagabrielle M Benoit et al ldquoNewly identifiedsegments of the Pacific-Australia plate boundary along theNorth Fiji transform zonerdquo Earth and Planetary Science Lettersvol 193 no 3-4 pp 347ndash358 2001
[39] Y Fouquet E Pelleter C Konn et al ldquoVolcanic and hydrother-mal processes in submarine calderas the Kulo Lasi example(SW Pacificrdquo Ore Geology Reviews 2017 In Revision
[40] K L Von Damm J M Edmond B Grant C I Measures BWalden and R F Weiss ldquoChemistry of submarine hydrother-mal solutions at 21 ∘N East Pacific Riserdquo Geochimica et Cos-mochimica Acta vol 49 no 11 pp 2197ndash2220 1985
[41] J-L Charlou and J-P Donval ldquoHydrothermal methane ventingbetween 12∘N and 26∘N along the Mid-Atlantic Ridgerdquo Journalof Geophysical Research Atmospheres vol 98 no 6 pp 9625ndash9642 1993
[42] K Grasshoff ldquoA simultaneous multiple channel system fornutrient analysis in seawater with analog and digital datarecordrdquo inAdvances inAutomatedAnalysis pp 135ndash145MediadInc New York NY USA 1970
[43] J B Mullin and J P Riley ldquoThe colorimetric determinationof silicate with special reference to sea and natural watersrdquoAnalytica Chimica Acta vol 12 no C pp 162ndash176 1955
[44] E Baltussen P Sandra F David and C Cramers ldquoStir barsorptive extraction (SBSE) a novel extraction technique foraqueous samples theory and principlesrdquo Journal of Microcol-umn Separations vol 11 no 10 pp 737ndash747 1999
[45] C R German and K L VonDamm ldquoHydrothermal ProcessesrdquoTreatise on Geochemistry vol 6-9 pp 181ndash222 2004
[46] K L Von Damm J L Bischoff and R J Rosenbauer ldquoQuartzsolubility in hydrothermal seawater an experimental study andequation describing quartz solubility for up to 05 M NaClsolutionsrdquoAmerican Journal of Science vol 291 no 10 pp 977ndash1007 1991
[47] J L Bischoff and R J Rosenbauer ldquoThe critical point and two-phase boundary of seawater 200-500∘Crdquo Earth and PlanetaryScience Letters vol 68 no 1 pp 172ndash180 1984
[48] K LVonDamm ldquoSeafloor hydrothermal activity black smokerchemistry and chimneysrdquo Annual Review of Earth amp PlanetarySciences vol 18 pp 173ndash204 1990
[49] J L Bischoff and R J Rosenbauer ldquoPhase separation in seafloorgeothermal systems an experimental study of the effects onmetal transportrdquo American Journal of Science vol 287 no 10pp 953ndash978 1987
[50] YMei DM ShermanW Liu B EtschmannD Testemale andJ Brugger ldquoZinc complexation in chloride-rich hydrothermalfluids (25-600∘C) A thermodynamic model derived from abinitio molecular dynamicsrdquo Geochimica et Cosmochimica Actavol 150 pp 265ndash284 2015
[51] N J Pester K Ding and W E Seyfried ldquoVapor-liquid par-titioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids An experimental study from
360 to 465∘C near-critical to halite saturated conditionsrdquoGeochimica et Cosmochimica Acta vol 168 pp 111ndash132 2015
[52] M Watanabe T Sato H Inomata et al ldquoChemical reactionsof C1 compounds in near-critical and supercritical waterrdquoChemical Reviews vol 104 no 12 pp 5803ndash5821 2004
[53] J L Bischoff and K S Pitzer ldquoLiquid-vapor relations for thesystem NaCl-H2O summary of the P-T- x surface from 300∘ to500∘CrdquoAmerican Journal of Science vol 289 no 3 pp 217ndash2481989
[54] D I Foustoukos and W E Seyfried Jr ldquoQuartz solubilityin the two-phase and critical region of the NaCl-KCl-H2Osystem Implications for submarine hydrothermal vent systemsat 9∘501015840N East Pacific Riserdquo Geochimica et Cosmochimica Actavol 71 no 1 pp 186ndash201 2007
[55] S D Scott ldquoChapter 16 Submarine hydrthermal systems anddepositsrdquo in Geochemistry of Hydrothermal Ore Deposits H LBarnes Ed pp 797ndash876 3rd edition 1997
[56] M J Mottl J S Seewald C G Wheat et al ldquoChemistry of hotsprings along the Eastern Lau Spreading Centerrdquo Geochimica etCosmochimica Acta vol 75 no 4 pp 1013ndash1038 2011
[57] T Gamo K Okamura J-L Charlou et al ldquoAcidic sulfate-richhydrothermal fluids from theManus back-arc basin PapuaNewGuineardquo Geology vol 25 no 2 pp 139ndash142 1997
[58] D A Butterfield K-I Nakamura B Takano et al ldquoHigh SO2flux sulfur accumulation and gas fractionation at an eruptingsubmarine volcanordquo Geology vol 39 no 9 pp 803ndash806 2011
[59] C E J de Ronde G J Massoth D A Butterfield et alldquoSubmarine hydrothermal activity and gold-richmineralizationat Brothers Volcano Kermadec Arc New ZealandrdquoMineraliumDeposita vol 46 no 5 pp 541ndash584 2011
[60] C E J de Ronde and V K Stucker ldquoChapter 47 - Seafloorhydrothermal venting at volcanic arcs and backarcs A2rdquo inTheEncyclopedia of Volcanoes Haraldur Sigurdsson Ed pp 823ndash849 Academic Press Amsterdam Netherlands 2nd edition2015
[61] F J Sansone J A Resing G W Tribble P N Sedwick K MKelly and K Hon ldquoLava-seawater interactions at shallow-watersubmarine lava flowsrdquo Geophysical Research Letters vol 18 no9 pp 1731ndash1734 1991
[62] M J Mottl H D Holland and R F Corr ldquoChemical exchangeduring hydrothermal alteration of basalt by seawater-II Exper-imental results for Fe Mn and sulfur speciesrdquo Geochimica etCosmochimica Acta vol 43 no 6 pp 869ndash884 1979
[63] W E Seyfried N Pester and Q Fu ldquoPhase Equilibria Controlson theChemistry ofVent Fluids fromHydrothermal Systems onSlow Spreading Ridges Reactivity Of Plagioclase and OlivineSolid Solutions and the pH-Silica Connectionrdquo Diversity ofHydrothermal Systems on Slow Spreading Ocean Ridges pp 297ndash320 2013
[64] P Jean-Baptiste J L Charlou M Stievenard J P Donval HBougault and C Mevel ldquoHelium and methane measurementsin hydrothermal fluids from the mid-Atlantic ridge The SnakePit site at 23∘Nrdquo Earth and Planetary Science Letters vol 106no 1-4 pp 17ndash28 1991
[65] P Jean-Baptiste E Fourre J-L Charlou C R German and JRadford-Knoery ldquoHelium isotopes at the Rainbow hydrother-mal site (Mid-Atlantic Ridge 36∘141015840N)rdquo Earth and PlanetaryScience Letters vol 221 no 1-4 pp 325ndash335 2004
[66] J Lupton K H Rubin R Arculus et al ldquoHelium isotopeC3He andBa-Nb-Ti signatures in the northern LauBasinDis-tinguishing arc back-arc and hotspot affinitiesrdquo GeochemistryGeophysics Geosystems vol 16 no 4 pp 1133ndash1155 2015
Geofluids 23
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
[67] G P Glasby ldquoAbiogenic origin of hydrocarbons An historicaloverviewrdquo Resource Geology vol 56 no 1 pp 83ndash96 2006
[68] V G Kutcherov and V A Krayushkin ldquoDeep-seated abiogenicorigin of petroleum From geological assessment to physicaltheoryrdquo Reviews of Geophysics vol 48 no 1 Article ID RG10012010
[69] G Proskurowski M D Lilley J S Seewald et al ldquoAbiogenichydrocarbon production at lost city hydrothermal fieldrdquo Sci-ence vol 319 no 5863 pp 604ndash607 2008
[70] B Sherwood Lollar T D Westgate J A Ward G F Slaterand G Lacrampe-Couloume ldquoAbiogenic formation of alkanesin the earthrsquos crust as a minor source for global hydrocarbonreservoirsrdquo Nature vol 416 no 6880 pp 522ndash524 2002
[71] S Sherwood Lollar G Lacrampe-Couloume K Voglesonger TC Onstott L M Pratt and G F Slater ldquoIsotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites A model for abiogenic polymerization of hydrocarbonsrdquoGeochimica et CosmochimicaActa vol 72 no 19 pp 4778ndash47952008
[72] G Etiope S Vance L E Christensen J M Marques and IRibeiro da Costa ldquoMethane in serpentinized ultramafic rocksin mainland Portugalrdquo Marine and Petroleum Geology vol 45pp 12ndash16 2013
[73] M J Whiticar ldquoCarbon and hydrogen isotope systematicsof bacterial formation and oxidation of methanerdquo ChemicalGeology vol 161 no 1 pp 291ndash314 1999
[74] C Konn J L Charlou N G Holm and O Mousis ldquoTheproduction of methane hydrogen and organic compoundsin ultramafic-hosted hydrothermal vents of the mid-atlanticridgerdquo Astrobiology vol 15 no 5 pp 381ndash399 2015
[75] O E Kawka and B R T Simoneit ldquoPolycyclic aromatichydrocarbons in hydrothermal petroleums from the GuaymasBasin spreading centerrdquoAppliedGeochemistry vol 5 no 1-2 pp17ndash27 1990
[76] B R T Simoneit ldquoChapter 4 Aqueous organic geochemistry athigh temperaturehigh pressurerdquo Origins of Life and Evolutionof Biospheres vol 22 no 1-4 pp 43ndash65 1992
[77] J S Seewald W E Seyfried Jr and E C Thornton ldquoOrganic-rich sediment alteration an experimental and theoretical studyat elevated temperatures and pressuresrdquo Applied Geochemistryvol 5 no 1-2 pp 193ndash209 1990
[78] M D Schulte and E L Shock ldquoAldehydes in hydrothermalsolution Standard partial molal thermodynamic propertiesand relative stabilities at high temperatures and pressuresrdquoGeochimica et CosmochimicaActa vol 57 no 16 pp 3835ndash38461993
[79] J S Seewald ldquoAqueous geochemistry of low molecularweight hydrocarbons at elevated temperatures and pressuresConstraints from mineral buffered laboratory experimentsrdquoGeochimica et Cosmochimica Acta vol 65 no 10 pp 1641ndash16642001
[80] B R T Simoneit W D Goodfellow and J M FranklinldquoHydrothermal petroleum at the seafloor and organic matteralteration in sediments ofMiddle Valley Northern Juan de FucaRidgerdquo Applied Geochemistry vol 7 no 3 pp 257ndash264 1992
[81] O E Kawka and B R T Simoneit ldquoHydrothermal pyroly-sis of organic matter in Guaymas Basin I Comparison ofhydrocarbon distributions in subsurface sediments and seabedpetroleumsrdquo Organic Geochemistry vol 22 no 6 pp 947ndash9781994
[82] B R T Simoneit O E Kawka and M Brault ldquoOrigin of gasesand condensates in the Guaymas Basin hydrothermal system
(Gulf of California)rdquo Chemical Geology vol 71 no 1-3 pp 169ndash182 1988
[83] Y V Kissin ldquoCatagenesis and composition of petroleumOriginof n-alkanes and isoalkanes in petroleum crudesrdquoGeochimica etCosmochimica Acta vol 51 no 9 pp 2445ndash2457 1987
[84] T M McCollom and J S Seewald ldquoCarbon isotope composi-tion of organic compounds produced by abiotic synthesis underhydrothermal conditionsrdquo Earth and Planetary Science Lettersvol 243 no 1-2 pp 74ndash84 2006
[85] S C Vishnoi S D Bhagat V B Kapoor S K Chopra andR Krishna ldquoSimple gas chromatographic determination ofthe distribution of normal alkanes in the kerosene fraction ofpetroleumrdquo Analyst vol 112 no 1 pp 49ndash52 1987
[86] B R T Simoneit ldquoPetroleum generation in submarinehydrothermal systems an updaterdquo The Canadian Mineralogistvol 26 pp 827ndash840 1988
[87] J B Rapp ldquoA statistical approach to the interpretation ofaliphatic hydrocarbon distributions in marine sedimentsrdquoChemical Geology vol 93 no 1-2 pp 163ndash177 1991
[88] N Akiya and P E Savage ldquoRoles of water for chemical reactionsin high-temperature waterrdquo Chemical Reviews vol 102 no 8pp 2725ndash2750 2002
[89] S Deguchi and K Tsujii ldquoSupercritical water A fascinatingmedium for soft matterrdquo Soft Matter vol 3 no 7 pp 797ndash8032007
[90] J P Ferris ldquoChapter 6 Chemical markers of prebiotic chemistryin hydrothermal systemsrdquo Origins of Life and Evolution ofBiospheres vol 22 no 1-4 pp 109ndash134 1992
[91] D I Foustoukos and J C Stern ldquoOxidation pathways forformic acid under low temperature hydrothermal conditionsImplications for the chemical and isotopic evolution of organicson Marsrdquo Geochimica et Cosmochimica Acta vol 76 pp 14ndash282012
[92] T M McCollom and J S Seewald ldquoExperimental constraintson the hydrothermal reactivity of organic acids and acid anionsI Formic acid and formaterdquo Geochimica et Cosmochimica Actavol 67 no 19 pp 3625ndash3644 2003
[93] T M McCollom and J S Seewald ldquoExperimental study ofthe hydrothermal reactivity of organic acids and acid anionsII Acetic acid acetate and valeric acidrdquo Geochimica et Cos-mochimica Acta vol 67 no 19 pp 3645ndash3664 2003
[94] D E Ingmanson and M J Dowler ldquoChemical evolution andthe evolution of the Earthrsquos crustrdquo Origins of Life vol 8 no 3pp 221ndash224 1977
[95] N G Holm and J L Charlou ldquoInitial indications of abi-otic formation of hydrocarbons in the Rainbow ultramafichydrothermal systemMid-Atlantic Ridgerdquo Earth and PlanetaryScience Letters vol 191 no 1-2 pp 1ndash8 2001
[96] P E Rossel A Stubbins T Rebling A Koschinsky J AHawkes and T Dittmar ldquoThermally altered marine dissolvedorganic matter in hydrothermal fluidsrdquo Organic Geochemistryvol 110 pp 73ndash86 2017
[97] J G Ferry ldquoThe chemical biology ofmethanogenesisrdquoPlanetaryand Space Science vol 58 no 14-15 pp 1775ndash1783 2010
[98] Y J Kim H S Lee E S Kim et al ldquoFormate-driven growthcoupledwithH2 productionrdquoNature vol 467 no 7313 pp 352ndash355 2010
[99] S Q Lang G L Fruh-Green SM Bernasconi et al ldquoMicrobialutilization of abiogenic carbon and hydrogen in a serpentinite-hosted systemrdquo Geochimica et Cosmochimica Acta vol 92 pp82ndash99 2012
24 Geofluids
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
[100] T Windman N Zolotova F Schwandner and E L ShockldquoFormate as an energy source for microbial metabolism inchemosynthetic zones of hydrothermal ecosystemsrdquo Astrobiol-ogy vol 7 no 6 pp 873ndash890 2007
[101] A Galushko D Minz B Schink and F Widdel ldquoAnaerobicdegradation of naphthalene by a pure culture of a noveltype of marine sulphate-reducing bacteriumrdquo EnvironmentalMicrobiology vol 1 pp 415ndash420 1999
[102] S A Bennett C V Dover J A Breier and M ColemanldquoEffect of depth and vent fluid composition on the carbonsources at two neighboring deep-sea hydrothermal vent fields(Mid-Cayman Rise)rdquo Deep-Sea Research Part I OceanographicResearch Papers vol 104 pp 122ndash133 2015
[103] S A Bennett E P Achterberg D P Connelly P J Statham GR Fones and C R German ldquoThe distribution and stabilisationof dissolved Fe in deep-sea hydrothermal plumesrdquo Earth andPlanetary Science Letters vol 270 no 3-4 pp 157ndash167 2008
[104] P F Greenwood J J Brocks K Grice et al ldquoOrganic geo-chemistry andmineralogy I Characterisation of organicmatterassociated with metal depositsrdquo Ore Geology Reviews vol 50pp 1ndash27 2013
[105] W Liu D C McPhail and J Brugger ldquoAn experimentalstudy of copper(I)-chloride and copper(I)-acetate complexingin hydrothermal solutions between 50∘C and 250∘ and vapor-saturated pressurerdquo Geochimica et Cosmochimica Acta vol 65no 17 pp 2937ndash2948 2001
[106] D A Palmer and K E Hyde ldquoAn experimental determinationof ferrous chloride and acetate complexation in aqueous solu-tions to 300∘Crdquo Geochimica et Cosmochimica Acta vol 57 no7 pp 1393ndash1408 1993
[107] S P Franklin A Hajash Jr T A Dewers and T T Tieh ldquoTherole of carboxylic acids in albite and quartz dissolution Anexperimental study under diagenetic conditionsrdquoGeochimica etCosmochimica Acta vol 58 no 20 pp 4259ndash4279 1994
[108] H G Machel H R Krouse and R Sassen ldquoProducts anddistinguishing criteria of bacterial and thermochemical sulfatereductionrdquo Applied Geochemistry vol 10 no 4 pp 373ndash3891995
[109] B R T Simoneit M Brault and A Saliot ldquoHydrocarbonsassociated with hydrothermal minerals vent waters and taluson the East Pacific Rise and Mid-Atlantic Ridgerdquo AppliedGeochemistry vol 5 no 1-2 pp 115ndash124 1990
[110] J A Resing P N Sedwick C R German et al ldquoBasin-scaletransport of hydrothermal dissolved metals across the SouthPacific Oceanrdquo Nature vol 523 no 7559 pp 200ndash203 2015
[111] S Roshan and J Wu ldquoThe distribution of dissolved copper inthe tropical-subtropical north Atlantic across the GEOTRACESGA03 transectrdquoMarine Chemistry vol 176 pp 189ndash198 2015
[112] A Tagliabue L Bopp J-C Dutay et al ldquoHydrothermalcontribution to the oceanic dissolved iron inventoryrdquo NatureGeoscience vol 3 no 4 pp 252ndash256 2010
[113] J Wu S Roshan and G Chen ldquoThe distribution of dissolvedmanganese in the tropical-subtropical North Atlantic duringUSGEOTRACES 2010 and 2011 cruisesrdquoMarine Chemistry vol166 pp 9ndash24 2014
[114] J E Lupton R J Arculus J Resing et al ldquoHydrothermal activityin the Northwest Lau Backarc Basin Evidence from watercolumn measurementsrdquo Geochemistry Geophysics Geosystemsvol 13 no 1 Article ID Q0AF04 2012
[115] H Elderfield and A Schultz ldquoMid-ocean ridge hydrothermalfluxes and the chemical composition of the oceanrdquo Annual
Review of Earth and Planetary Sciences vol 24 pp 191ndash2241996
[116] C R German A M Thurnherr J Knoery J-L Charlou PJean-Baptiste andH N Edmonds ldquoHeat volume and chemicalfluxes from submarine venting A synthesis of results from theRainbow hydrothermal field 36∘N MARrdquo Deep-Sea ResearchPart I Oceanographic Research Papers vol 57 no 4 pp 518ndash527 2010
[117] EMittelstaedt J EscartınNGracias et al ldquoQuantifying diffuseand discrete venting at the Tour Eiffel vent site Lucky Strikehydrothermal fieldrdquo Geochemistry Geophysics Geosystems vol13 no 4 Article ID Q04008 2012
[118] J Sarrazin P Rodier M K Tivey H Singh A Schultz andP M Sarradin ldquoA dual sensor device to estimate fluid flowvelocity at diffuse hydrothermal ventsrdquo Deep-Sea Research PartI Oceanographic Research Papers vol 56 no 11 pp 2065ndash20742009
[119] K G Speer and J Marshall ldquoThe growth of convective plumesat seafloor hot springsrdquo Journal of Marine Research vol 53 no6 pp 1025ndash1057 1995
[120] M Visbeck J Marshall and H Jones ldquoDynamics of isolatedconvective regions in the oceanrdquo Journal of Physical Oceanog-raphy vol 26 no 9 pp 1721ndash1734 1996
[121] J A Whitehead J Marshall and G E Hufford ldquoLocalizedconvection in rotating stratified fluidrdquo Journal of GeophysicalResearch Oceans vol 101 no 11 pp 25705ndash25721 1996
[122] D R Jackett and T J Mcdougall ldquoMinimal Adjustment ofHydrographic Profiles to Achieve Static Stabilityrdquo Journal ofAtmospheric and Oceanic Technology vol 12 pp 381ndash389 1995
[123] P Derian C F Mauzey and S D Mayor ldquoWavelet-basedoptical flow for two-component wind field estimation fromsingle aerosol lidar datardquo Journal of Atmospheric and OceanicTechnology vol 32 no 10 pp 1759ndash1778 2015
[124] G Carazzo A M Jellinek and A V Turchyn ldquoThe remarkablelongevity of submarine plumes Implications for the hydrother-mal input of iron to the deep-oceanrdquo Earth and PlanetaryScience Letters vol 382 pp 66ndash76 2013
[125] I Bauer and H-J Knolker ldquoIron Complexes in OrganicChemistryrdquo Iron Catalysis in Organic Chemistry Reactions andApplications pp 1ndash27 2008
[126] E T Baker G J Massoth S L Walker and R W EmbleyldquoA method for quantitatively estimating diffuse and discretehydrothermal dischargerdquo Earth and Planetary Science Lettersvol 118 no 1-4 pp 235ndash249 1993
[127] P Ramondenc L N Germanovich K L Von Damm and R PLowell ldquoThe first measurements of hydrothermal heat output at9∘501015840N East Pacific Riserdquo Earth and Planetary Science Lettersvol 245 no 3-4 pp 487ndash497 2006
[128] P Jean-Baptiste H Bougault A Vangriesheim et al ldquoMantle3He in hydrothermal vents and plume of the Lucky Strike site(MAR 37∘171015840N) and associated geothermal heat fluxrdquo Earth andPlanetary Science Letters vol 157 no 1-2 pp 69ndash77 1998
[129] A Schultz and H Elderfield ldquoControls on the physics andchemistry of seafloor hydrothermal circulationrdquo PhilosophicalTransactions of the Royal Society of London A MathematicalPhysical and Engineering Sciences vol 355 no 1723 pp 387ndash425 1997
[130] C A Stein and S Stein ldquoConstraints on hydrothermal heat fluxthrough the oceanic lithosphere from global heat flowrdquo Journalof Geophysical Research Atmospheres vol 99 no 2 pp 3081ndash3095 1994
Geofluids 25
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
[131] E T Baker J A Resing R M Haymon et al ldquoHow many ventfields New estimates of vent field populations on ocean ridgesfrom precise mapping of hydrothermal discharge locationsrdquoEarth and Planetary Science Letters vol 449 pp 186ndash196 2016
[132] D A Stolper A MMartini M Clog et al ldquoDistinguishing andunderstanding thermogenic and biogenic sources of methaneusing multiply substituted isotopologuesrdquo Geochimica et Cos-mochimica Acta vol 161 pp 219ndash247 2015
[133] A Gilbert K Yamada K Suda Y Ueno and N YoshidaldquoMeasurement of position-specific 13C isotopic composition ofpropane at the nanomole levelrdquo Geochimica et CosmochimicaActa vol 177 pp 205ndash216 2016
[134] S Kawagucci Y Ueno K Takai et al ldquoGeochemical originof hydrothermal fluid methane in sediment-associated fieldsand its relevance to the geographical distribution of wholehydrothermal circulationrdquo Chemical Geology vol 339 pp 213ndash225 2013
[135] M Blumenberg R Seifert S Petersen and W MichaelisldquoBiosignatures present in a hydrothermal massive sulfide fromthe Mid-Atlantic Ridgerdquo Geobiology vol 5 no 4 pp 435ndash4502007
[136] J E Cooper and E E Bray ldquoA postulated role of fatty acids inpetroleum formationrdquo Geochimica et Cosmochimica Acta vol27 no 11 pp 1113ndash1127 1963
[137] F Ben-Mlih J-C Marty and A Fiala-Medioni ldquoFatty acidcomposition in deep hydrothermal vent symbiotic bivalvesrdquoJournal of Lipid Research vol 33 no 12 pp 1797ndash1806 1992
