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IGEM 15/04/2011 1
Lithocap alteration and sulfidation state evolution of ores over porphyry systems:
IGEM Moscow: April 2011IGEM Moscow: April 2011
Insight from volcanic-hydrothermal systems
Jeffrey W. HedenquistJeffrey W. Hedenquisty qy qOttawa, CanadaOttawa, Canada
Thanks to Kinross Gold CorporationThanks to Kinross Gold Corporation
White Island, New ZealandWhite Island, New Zealand
•• Evolution of hydrothermal alteration and mineralizationEvolution of hydrothermal alteration and mineralization•• Advanced argillic alteration: Condensation of magmatic vaporAdvanced argillic alteration: Condensation of magmatic vapor
•• Mineralization of high & intermediate sulfidation state mineralsMineralization of high & intermediate sulfidation state minerals
•• Evolution of magmaticEvolution of magmatic hydrothermal fluidshydrothermal fluids•• Evolution of magmaticEvolution of magmatic--hydrothermal fluidshydrothermal fluidsHigh-temperature hypogene vapors, ~850 oC (HCl, SO2)
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IGEM 15/04/2011 2
H2SO4 HCl Hypogene
Lithocap formed by hypogene condensate
Formation of advanced argillic alteration
H2SO4, HCl HypogenepH <1
HCl, SO2, CO2, H2Shypogene alteration
4 SO2 + 4 H2O => 3 H2SO4 + H2S
H2O, NaCl, SO2, HCl, CO2, H2S, ...
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IGEM 15/04/2011 3
Summitville, Colorado
aluminoalumino-- qtzqtz-- residual residual qtzqtz--silicatessilicates alunalun-- qtzqtz alunalun--(kandites)(kandites) pyritepyrite pyritepyrite
residual residual qtzqtz--alunalun--qtzqtz pyritepyrite
( )( ) pypy pypy
Summitville, Colorado
Residual (vuggy) qtz and Residual (vuggy) qtz and qtzqtz--alunite flares upwardalunite flares upward
Residual (vuggy) qtz (ore)Residual (vuggy) qtz (ore)QtzQtz--alunitealunite--pypy
Steven and Ratté, 1960
Steven & Ratté, 1960
pH ~ >6 4 - 6 2 - 4 <2
10 - 100s m
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Far Southeast Far Southeast –– Lepanto, Phillipines: Lepanto, Phillipines: Linked porphyry and epithermal depositsLinked porphyry and epithermal depositsFar Southeast Far Southeast –– Lepanto, Phillipines: Lepanto, Phillipines: Linked porphyry and epithermal depositsLinked porphyry and epithermal deposits
Mohong Hill quartz-alunite-pyrite lithocapalunite pyrite lithocap
dacite pyroclasticsdacite pyroclastics
volcaniclastic volcaniclastic basementbasement
Lepanto cross section:Lepanto cross section:
Early alteration flares Early alteration flares upward along structure, upward along structure, and outward from feederand outward from feeder
Dacite pyroclastc
and outward from feeder and outward from feeder along unconformityalong unconformity
quartz
LithologyLithology--controlled controlled lithocap lithocap outcropoutcrop
Basement volcaniclastics
Enargite-Au ore in residual qtz host
Quartz-alunite-py ± Al-silicate halo
FreshFresh QtzQtz alunalun VuggyVuggy
Gonzalez, 1956, 1959; Garcia,
Fresh Fresh QtzQtz--alunalun-- Vuggy Vuggy dacite dacite py halopy halo qtz oreqtz ore
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IGEM 15/04/2011 5
Satsuma Iwojima, S. Kyushu:Satsuma Iwojima, S. Kyushu:passive degassingpassive degassing 870 870 ooC HC H22O, O,
HCl, SOHCl, SO22
Summit craterSummit craterSampling of 770 C vapor with acidic gases,HCl, SO2
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Residual (vuggy) qtzResidual (vuggy) qtzSatsuma Iwojima, Japan
pH 1.7 -- 1.1
Hedenquist et al., 1994
dissolved rock pH 1.1pH 1.1
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Dissociation and increased Dissociation and increased reactivity due to coolingreactivity due to cooling
HCl HCl ⇒⇒ HH++ + Cl+ Cl--HH22SOSO44 ⇒⇒ HH++ + HSO4+ HSO4--
~100 m~100 m
silicicsilicicqtzqtz--alunalun muscovite overprint, muscovite overprint,
transition up to pyrophyllitetransition up to pyrophyllite
150 C 200 C 250 C pH~1.5 ~0.7 ~1
300 CpH~2
W:R <10 W:R >>10
Hypogene acidHypogene acid--leached leached horizon = lithocaphorizon = lithocap
Magmatic condensates more reactive with rock at lower temperature (and high W:R ratio)
350 C350 C
Lepanto Lepanto -- Far Southeast, Philippines:Far Southeast, Philippines:(1 Mt Cu, 4 Moz Au; 5 Mt Cu, 20 Moz Au) (1 Mt Cu, 4 Moz Au; 5 Mt Cu, 20 Moz Au)
Offset of lithocap, and ore, from causative intrusionOffset of lithocap, and ore, from causative intrusion
Hedenquist et al., 1998Hedenquist and Taran 2011
200 C200 C
300 C300 C
Long section along Lepanto faultLong section along Lepanto fault
Hedenquist and Taran, 2011
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Mankayan Mankayan district, district, Luzon: Luzon:
LepantoLepanto LepantoLepanto Lepanto enargiteenargite--Au, Au, Far Southeast Far Southeast porphyry Cuporphyry Cu--Au, and Au, and Victoria veinsVictoria veins
Lepanto
Far Southeast
Victoria
1 km
Surface projections of Surface projections of Lepanto enargiteLepanto enargite--Au Au deposit, Victoria veins, & deposit, Victoria veins, & Far Southeast porphyryFar Southeast porphyry
X Horn1.45 Ma
Hydro Biot1.40-1.45 Ma
Alunite1.40-1.45 Ma
Ser ~1.35 Ma
Bt 2.2-1.8 Ma
Enargite-AuPorphyry Cu
ArribasArribas et al. (1995); et al. (1995); Cla eriaCla eria (2001)(2001)
Teresaveins
Bulalacao porphyry
X Biot1.18 Ma
X Illite 1.15-1.4 Ma
IS Au-Ag veinsClaveriaClaveria (2001); (2001); Hedenquist et al. (2001)Hedenquist et al. (2001)
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Einaudi et al., 2003
Sulfidation statesSulfidation states
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Einaudi et al., 2003
Sulfidation state evolutionSulfidation state evolution Arc Arc magmasmagmasResidual quartz
(secondary quartzite)
Magmas of Magmas of bimodal bimodal
extensionextension
No rock buffer left
e.g., Lepanto, Kochbulak, Bereznyaki
Kovalenker et al., 1997 Hedenquist et al., 1998Plotinskaya et al., 2009
White Island, New Zealand: Quiescent eruption 1988White Island, New Zealand: Quiescent eruption 1988
SulfidationSulfidationand and redoxredoxstatesstates
Vapor condensates Vapor condensates cause acidic leaching.cause acidic leaching.
What more can we learn What more can we learn statesstatesfrom volcanic fluids?from volcanic fluids?
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Active and extinct volcanic systemsActive and extinct volcanic systemsGiggenbach, 1987Giggenbach, 1987
lfur condensationT ( C)o100 300 500 800
-2
2 arc magmas
lfur condensationT ( C)o100 300 500 800
-2
2 arc magmas
lfur condensationT ( C)o100 300 500 800
-2
2 arc magmas
lfur condensationT ( C)o100 300 500 800
-2
2 arc magmas
lfur condensationT ( C)o100 300 500 800
-2
2 arc magmas
Einaudi, Hedenquist, Einaudi, Hedenquist, Inan, 2003Inan, 2003
bn
cvdg
Sulfur
poiro
n
tn
mt+qz+po
fayalite
-6
-10
bn
cvdg
Sulfur
poiro
n
tn
mt+qz+po
fayalite
-6
-10
bn
cvdg
Sulfur
poiro
n
tn
mt+qz+po
fayalite
-6
-10
FUMAROLES
MAGMATIC HYDROTHERMAL
bn
cvdg
Sulfur
poiro
n
tn
mt+qz+po
fayalite
-6
-10
FUMAROLES
bn
cvdg
Sulfur
poiro
n
tn
mt+qz+po
fayalite
-6
-10
FUMAROLES
HS
epith
erm
alba
se-m
etal
vei
ns
Porphyry-Cu
py + bn
cp
po
lo+po
hm + py
mt
1000/T (K)3.0 2.0 1.0
-14
-18
py + bn
cp
po
lo+po
hm + py
mt
1000/T (K)3.0 2.0 1.0
-14
-18
py + bn
cp
po
lo+po
hm + py
mt
1000/T (K)3.0 2.0 1.0
-14
-18
py + bn
cp
po
lo+po
hm + py
mt
1000/T (K)3.0 2.0 1.0
-14
-18
py + bn
cp
po
lo+po
hm + py
mt
1000/T (K)3.0 2.0 1.0
-14
-18
T ( C)o100 300 500 800
h
hm
py + bn + hmcp
OXIDIZEDT ( C)o100 300 500 800
h
hm
py + bn + hmcp
T ( C)o100 300 500 800
h
hm
py + bn + hmcp
T ( C)o100 300 500 800
h
hm
py + bn + hmcp
T ( C)o100 300 500 800
h
hm
py + bn + hmcp
T ( C)o100 300 500 800
h
hm
py + bn + hmcp
acid crater-lakesT ( C)o100 300 500 800
h
hm
py + bn + hmcp
acid crater-lakesT ( C)o100 300 500 800
h
hm
py + bn + hmcp
acid crater-lakes
RRH H (log (log ffHH22//ffHH22O) O) -- 1/T “Gigggegram”1/T “Gigggegram”Inan, Einaudi, Inan, Einaudi, Hedenquist, 2002Hedenquist, 2002
oxidizedoxidizedhmmt
mt + Spo
pyhm + Spy
NiO
p
Kspar + mt + qzphlogopite
hmmt
mt + Spo
pyhm + Spy
p
Kspar + mt + qzphlogopite
hmmt
mt + Spo
pyhm + Spy
p
Kspar + mt + qzphlogopite
hmmt
mt + Spo
pyhm + Spy
p
Kspar + mt + qzphlogopite
hmmt
mt + Spo
pyhm + Spy
p
Kspar + mt + qzphlogopite
hmmt
mt + Spo
pyhm + Spy
p
Kspar + mt + qzphlogopite
MAGMATIC HYDROTHERMAL
hmmt
mt + Spo
pyhm + Spy
p
Kspar + mt + qzphlogopite
MAGMATIC HYDROTHERMAL
hmmt
mt + Spo
pyhm + Spy
p
Kspar + mt + qzphlogopite
MAGMATIC HYDROTHERMAL f f OO22
reducedreduced
1000/T (K)3.0 1.01.41.82.22.6
mt + qzfayalite
NiONimt + py
po
REDUCED
1000/T (K)3.0 1.01.41.82.22.6
mt + qzfayalite
NiONimt + py
po
1000/T (K)3.0 1.01.41.82.22.6
mt + qzfayalite
NiONimt + py
po
1000/T (K)3.0 1.01.41.82.22.6
mt + qzfayalite
NiONimt + py
po
1000/T (K)3.0 1.01.41.82.22.6
mt + qzfayalite
NiONimt + py
po
1000/T (K)3.0 1.01.41.82.22.6
mt + qzfayalite
NiONimt + py
po
1000/T (K)3.0 1.01.41.82.22.6
mt + qzfayalite
NiONimt + py
po
1000/T (K)3.0 1.01.41.82.22.6
mt + qzfayalite
NiONimt + py
poGiggenbachs’‘rock buffer'
FeFe3+3+/Fe/Fe2+2+
reducedreduced
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Epithermal deposit endmember Epithermal deposit endmember chemical environments: chemical environments:
Sillitoe and Hedenquist, 2003La Coipa
Frutadel
Norte
Evolution affected by composition of magmatic fluid, and interaction with wallrock (many variations)
Norte
Kupol
Hedenquist et al., 2001
Geology of 3 end-member epithermal deposits: high-, intermediate- &
low-sulfidation ores
Geology of 3 end-member epithermal deposits: high-, intermediate- &
low-sulfidation ores
Dr. Glen Masterman, Vice President - Exploration
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IGEM 15/04/2011 13
Kinross deposits
Endowment of Endowment of Kinross deposits Kinross deposits that are >10 that are >10 Moz (300 t Au)Moz (300 t Au)
Source: Kinross and Red Back Mining Annual Reports and other sources.Deposit figures are quoted on a100% basis.
View Of La Coipa MineView Of La Coipa MineView over La Coipa Mine, Chile: to NW
Production: 1989-now, 108 t Au, 6030 t Ag; Resource: 57 t Au, 1770 t Ag
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- Alteration Steam heated, residual qtz,
advanced argillic (alunite), argillic
La Coipa, Chile: Geological characteristics of a high-sulfidation deposit
Domes
- Mineralization Styles Disseminated, breccia, veins, mantos
- Structural & lithological controls
- Hypogene mineralizationNative gold and silver, argentite, electrum, proustyte, pyrargyrite, pyrite, enargite, tetrahedrite, tennantite, chalcopyrite, bornite, galena, sphalerite: high sulfidation
- Supergene overprintNative gold and silver, cerargyrite, embolyte, iodargyrite, argento-jarosite
Domes
La Coipa: Ladera Farellón Cross Section
Qtz-alunite with roots of pyrophyllite ± zunyite, diaspore, APS (mica)
Pyrite-enargite (luzonite)-tennantite, pyrite-covellite/digenite, chalcocite/chalcopyritechalcocite/chalcopyrite, (+chalcopyrite, bornite, covellite, galena, sphalerite, tennantite)
(supergene overprint)
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Di (2006) f thDiscovery (2006) of theFruta del Norte epithermal Au/Ag deposit, Ecuador
LOCAL CRUSTAL STRUCTURESuarez pull-apart basin
SuarezFormation
Peñas FaultZone
Misahuallí Formation(main vein host)
FDN Juxtaposed
Suarez Fm
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Setting of Fruta del Norte
Cretaceous 119-110 Ma CretaceousCretaceous
Jurassic 170-190 Ma
Fruta del Norte 158-156 Ma
FRUTA DEL NORTE – BLIND TARGET – PATH-FINDER GEOCHEMISTRY
Suarez Fm: silicified - As, Sb, Hg, marcasite, BM
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THE DISCOVERY
Fruta del Norte MINERAL ZONESIntermediate Sulfidation Epithermal System:
R 204 t A (8 1 /t) AReserves: 204 t Au (8.1 g/t) Au
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LAMINATED SILICA SINTER/MUD POOL DEPOSITS
FDN-1 Mn-carbonate/rhodochrosite stockworks + BM7.43 g/t Au, 7.54 M oz (55% of orebody)
TEXTURES:- Crustiform-colloform-cockade-ginguroDiatreme breccia (dacite)
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FDN-2 Chalcedony marcasite + base metal sulphide7.31 g/t Au, 3.64 M oz (22% of orebody)
FEATURES:- >1% SULPHIDE (marcasite) – blackened fine matrix
FDN-3 Upper silica low sulphide carapace12.36 g/t Au, 0.4 M oz (2% of orebody)
FEATURES:- Depleted in sulphide, enriched in celadonite, locally vuggy
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FDN-4 Northern quartz vein zone6 g/t Au, 2.1 M oz (18% of orebody)
FEATURES:- Bladed carbonate (replaced) , adularia – intense stockworks - electrum
THE GOLD
FDN1…. 2447 g/t Au
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OkhotskOkhotsk--Chukotka metallogenyChukotka metallogeny
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Kupol regional geologyKupol regional geology
• Text• Text
Initial Occurrence Discovered in 1966 during Initial Occurrence Discovered in 1966 during 1:200,000 Regional Mapping Program1:200,000 Regional Mapping Program
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Kupol deposit discovered in 1995 Kupol deposit discovered in 1995 on last prospecting traverse of the seasonon last prospecting traverse of the season
Kupol DiscoveryKupol Discovery
Very little Very little outcrop of outcrop of ppKupol Vein. Kupol Vein. Big Bend Big Bend was buried was buried under talus under talus and tundra.and tundra.Vein float Vein float present in present in
th dth dnorth and north and south.south.
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Aerial View of Big Bend Aerial View of Big Bend ((40% of all gold at Kupol)40% of all gold at Kupol)
Kupol area geologyKupol area geology
Gently eastward dipping andesitic flows and pyroclastics, intruded by rhyolite dikes and flow dome complex
1 km
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Kupol Longitudinal Section, 2007Kupol Longitudinal Section, 2007(magnenta = 100 g*m Au )(magnenta = 100 g*m Au )
400 m
2003 to 2006, >150,000 m in 700 ddh define >180 t Au
Production, May 2008; development cost, $407 M
End 2010: 69 t Au equil.; Reserves, 75 t Au (10.7 g/t), 948 t Ag
Big BendBig Bend
• Single large vein• Single large vein• Steepening toward surface• Bisected by rhyolite dikes
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North ZoneNorth Zone
North and South Zones display near vertical multiple anastomosinganastomosing veins
Kupol mineralization stagesKupol mineralization stages
Early phase of quartz adularia (stained yellow) with minor goldyellow) with minor gold and silver
Second phase of sulfosalt-Second phase of sulfosaltrich quartz + adularia. Principal Au and Ag rich phase.
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Kupol “Bonanza” styles of mineralizationKupol “Bonanza” styles of mineralization
289 g/t Au, 3336 g/t Ag
Examples of high Examples of high grade sulfosaltgrade sulfosalt--rich rich colloform & colloform & crustiform banded crustiform banded veins and brecciasveins and breccias
237 g/t Au, 4291 g/t Ag
Main Ore MineralogyMain Ore Mineralogy•• Electrum, Native Gold, Native SilverElectrum, Native Gold, Native Silver•• Sulfosalts: Sulfosalts:
• Stephanite (Ag5SbS4) • Pyrargyrite (Ag3SbS3) • Tetrahedrite (Cu12Sb4S13) • Freibergite(Ag,Cu,Fe)12(Sb,As)4S13
• Perceite (Ag, Cu)16As2S11
•• Sulphides:Sulphides:A hi (A S)• Acanthite (Ag2S)
• Pyrite • Marcasite • Chalcopyrite • Sphalerite
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Low sulfidation deposit indicators: Vein formation at neutral pHLow sulfidation deposit indicators: Vein formation at neutral pH
Amorphous silica Amorphous silica depositiondepositionC liC li tiftifCyclic Cyclic crustiformcrustiformand and colloformcolloformbandingbanding
Sulfosalt rich Sulfosalt rich (ginguro) bands (ginguro) bands abundantabundant
HishikariHishikariKyushu, Japan:Kyushu, Japan:330 t Au, 40 g/t330 t Au, 40 g/t
10001000--4000 g/t Au4000 g/t Au~20 g/t Au~20 g/t Au
<1 g/t Au<1 g/t Au
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Kyushu tectonic evolutionKyushu tectonic evolution
Y. Watanabe, 2004Y. Watanabe, 2004
S Kyushu, looking south
• Tectonics influence type ypof epithermal Au deposit (early HS, IS, or later LS)
• Variable features, no single deposit type
Hishikari Hishikari (LS) 0.7 Ma(LS) 0.7 MaKushikino Kushikino
(IS) 3.7 Ma(IS) 3.7 Mamigration of volcanism
Epithermal deposit stylesEpithermal deposit styles
• Endmember styles can have a wide• Endmember styles can have a wide range of characteristics
• Variations caused by:• Tectonic setting• Magmatic affiliationg• Depth of formation and structural control• Degree of wallrock influence on paths of
fluid evolution
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IGEM 15/04/2011 30
Society of Economic Geologists (SEG)Society of Economic Geologists (SEG)Advancing Science & DiscoveryAdvancing Science & Discovery
•• Represents 6400 members in 105 countriesRepresents 6400 members in 105 countries•• Members from industry (~2/3) and research (~1/3)Members from industry (~2/3) and research (~1/3)•• Members from industry (~2/3) and research (~1/3)Members from industry (~2/3) and research (~1/3)•• Advance the science of economic geology Advance the science of economic geology •• HighHigh--quality conferences, seminars, publications (quality conferences, seminars, publications (Economic GeologyEconomic Geology))
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