ORIGIN OF URANIUM MINERALIZATION IN UNCONVENTIONAL GEOLOGICAL SETTINGS
Michel CUNEY
UNIVERSITE DE LORRAINE – GEORESSOURCESCREGU – CNRS
54 506, Vandoeuvre les NANCY FRANCE
METAMORPHICROCKS
M A N T L E
T °C
100100
200
300
400
600
25
800
CONTINENTAL
CRUST
Upper cont. crust
Primitive Mantle : 21ppb
Carb. chondrites : 7ppb
METAMORPHICROCKS
M A N T L E
T °C
100100
200
300
400
600
25
800
Primitive mantle : 21ppbCarb. chondrites : 7ppb
Calcretes/Lignite/Coal
PhosphatesBlack Shales
Conglomerates
RollfrontBasal
Breccia
TabularTectonolithologic
UnconformityPipes
HTMetamorphic
Na-metasomatism
LTMetamorphic
SEDIMENTARYROCKS
IGNEOUSROCKS
MagmaticMagmatic(crystal. fract)(
Veins
Volcanic
IOCG(U)
1.4 ppm U
2.7 ppm U
Enriched mantleHKCa
PAl
PAk
PAl
HKCa
.
HKCa
PAl
PAk
PAl
HKCaPAk
Depleted mantle
Alaskites
Skarns
Unconventional resourcesResources from which uranium is only recoverable as a minor by-product, such as :
� black shales and lignite,�uranium associated with phosphate rocks,� seawater� non-ferrous ores (porphyry copper, …), � carbonatite, � peralkaline intrusions, by product of REE production ?� monazite placers
A GENETIC CLASSIFICATION OF U-DEPOSITS (i)- I (M) MAGMATIC
• I.1 (MFC) fractional crystallization peralkaline Kvanefjeld, Greenland 135,000t@ 220ppm
• I.2 (MPM) partial melting granitic pegmatoids Rössing Namibia 246,500tU @300ppm
- II (H) HYDROTHERMAL
• II.1 (HV) hydrothermal-volcanic Streltsovkoye caldera (Russia): 250,000 t U at 0.10%
• II.2 (HG) hydrothermal-granitic Aue-Niederschlema, Germany 100,000 t U
• II.3 (HD) hydrothermal-diagenetic diagenetic brine circulation 3 sub-categories:
•II.3a (HDIa) with intraformational redox control:
o(HDIaTb) tabular Grants region, Colorado >240,000 t U @ 0.09-0.21 % mined
o(HDIaTl) tectonolithologic Lodève basin, France.
o(HDIaCb) dissolution-collapse breccias pipes Gd Canyon Arizona, USA
• II.3b (HDBb) with basement/basin redox control Athabasca, E Alligator River
• II.3c (HDIr) interformational redox boundary, Oklo, Gabon 27,[email protected]%
• II.4 (HMp) hydrothermal-metamorphic Shinkolobwe DRC 25 500tU, 0.40%
A GENETIC CLASSIFICATION OF U-DEPOSITS (ii)• II.5 (HMt) Hydrothermal-metasomatic
• II.5a (HMtNa) Na-metasomatism central Ukraine 180,000 t U
• II.5b (HMtK) K-metasomatism Elkon (Aldan, Russia) > 324,[email protected] % U±Au
• II.5c (HMtSk) Skarn-related contact/regional met. Mary Kathleen [email protected] %
- III (M) METEORIC WATER INFILTRATION with two sub-types:• III.1 (MB) Basal-type paleovalley or infiltration-type in Russia, Vitim district• III.2 (MRf) Roll fronts Kazakhstan with over 1 M t U resources
- IV (S) SYNSEDIMENTARY subdivided into 4 major types• IV.1 (SMs) Mechanical sorting Quartz Pebble Conglomerates Monazite placers• IV.2 (SRtm) Redox trapping in marine environments black shales. Sweden > 1 M t U
• IV.3 (SRtc) Redox trapping in contin envir coal, lignite, peat bog, swamp, anoxic lake
• IV.4 (SCcr) Crystal-chemical and redox trapping phosphorites up to 15-22 M t U
- V (E) EVAPOTRANSPIRATION = calcretes Langer Heinrich, Namibia 63 520 tU @ 510 ppm
- VI (O) OTHER TYPES Olympic Dam Fe-ox Cu-Au(U-Ag) (IOCG) S. Aust. 1.9 MtU @340ppm
� Peralkaline complexes
� Carbonatites (Palaborwa, South Africa)
� Intrusive U deposits (IAEA classif.) Porphyry Cu
(high-K calc-alkaline granites)
U deposits related to crystal fractionation
ppm Ultrabasic Basic Intermediate Granites X
U 0.021 0.75 2.4 3.3 x 160
Th 0.060 3.5 7.8 17.5Earth average Th/U = 4
INCOMPATIBLE BEHAVIOR
URANIUM FRACTIONATION FROM ULTRABASIC ROCKS TO GRANITES
U INCOMPATIBLE BEHAVIOUR
� several major geochemical and metallogenic consequences:
(i) U continuously transferred from the mantle to the Earth crust, & within the continental crust towards its upper part together with Th, K, …
(ii) the most felsic melts tend to be the most enriched in U,
(iii) granites & rhyolites � primary U sources for the formation of most U deposits, also unconventional deposits
Average granite (U= 3-4 ppm), U mainly in zircon, apatite, monazite, titanite, … from which U cannot be leached by most geological fluids � U enriched granites are needed as an efficient U source
Fondamental U fractionation processesI
O
N
I
C
R
D
I
U
S
COMPATIBLE
CORE
MAIN COORDINANCE
K-FELDSPAR –K-MICAS
ACCESSORYMINERALS
VALENCY1 2 3 4 5 6
1.5
12
8
6
4
0
0.5
1
2
< 1
> 50
15 – 50
1 – 15
Th 167U 156Zr 23Hf 21
Cr< 1
Se < 1
Ni < 1 V < 1 Ir < 1Os < 1
Pt < 1Ti < 1
Cu< 1
Al 4
Fe < 1Mn < 1
Mg < 1Sc < 1
Cs 205Rb 204
Ba 108K 156
Pb 167La 54
Ce 45 Pr 34Sm 43Nd 34
Y 6Lu 6
Na 12Sr 20
Ca 1
Mo 25
CONTINENTAL CRUST / C - CHONDRITE
COMPATIBLE
CORE
MAIN COORDINANCE
K-FELDSPAR –K-MICAS
VALENCY1 2 3 4 5 61 2 3 4 5 6
1.5
12
8
6
4
0
0.5
1
2
12
8
6
4
0
0.5
1
2
< 1
> 50
15 – 50
1 – 15
Th 167U 156Zr 23Hf 21
Cr< 1
Se < 1
Ni < 1 V < 1 Ir < 1Os < 1
Pt < 1Ti < 1
Cu< 1
Al 4
Fe < 1Mn < 1
Mg < 1Sc < 1
Cs 205Rb 204
Ba 108K 156
Pb 167La 54
Ce 45 Pr 34Sm 43Nd 34
Y 6Lu 6
Na 12Sr 20
Ca 1
Mo 25
CONTINENTAL CRUST / C - CHONDRITE
HFSE : HIGH FIELD STRESS ELEMENTS
Nb 45Ta 55Nb 45Ta 55
LILE : LARGE ION LITHOPHILE ELEMENTS
Al/(Na+K+2Ca) = A/CNK in cations= ASI Aluminium Saturation Index
Al/(Na+K) ou (Na+K) Al = AGPAICITY
why ?
= INDEX OF MAGMA POLYMERISATION
Magma aluminous indices to classify magmatic rocks
U-rich magma classification using aluminous indicessome specific granites have higher U contents
IMPOSSIBLECOMPOSITION
FIELD
PERALUMINOUS
PERALCALINE
METALUMINOUS
Al/(N
a+K)
Leucogranites(two micas)S-Type
High-KCalc-alkaline
A2 Type
quartz saturated& undersaturatedseries
A1 Type
feldspars
1.11
Al/(Na+K+2Ca)
Al/(Na+K) = 1 &Al/(Na+K+2Ca) = 1
whenAl-Na-K-Ca in feldspars only
Al/(Na+K+2Ca) > 1
� peraluminous
Al/(Na+K+2Ca) < 1
& Al/(Na+K) < 1
� peralkaline
Al/(Na+K+2Ca) >1
& Al/(Na+K) > 1
� calc-alkaline
1 .41 .00 .6 1 .81 0 0
1 0 1
1 0 2
1 0 3
1 0 4
1 0 5
Na+K/Al
Na2 CO3
HCl
NaCl
UO2 SOLUBILITY IN FELSIC MELTS
U (ppm)
in the
silicate
melt
Oxygen buffers
PERALUMINOUS PERALKALINEN i- NiO
H.M .
Cu 2O- C uO
NaF
HF
Peiffert et al., 1996
-4
-3
-2
0.6 1.30.90.80.7 1.1 1.21
-1
3
2
1
0
(Na+K+2Ca)/(Al.(Al+Si))
Ln(Σ
REE
/0.8
3)
metaluminous/peralkalineperaluminous
SHALES
MONAZITE SOLUBILITY IN SILICATE MELTS
from Montel, 1986
MANTLE
CONTINENTALCRUST
Cationic ratio : M = [(Na+K+2Ca)/(Al*Si)]
Zr
(pp
m)
Watson, E.B., Harrison, T.M., 1983. Zircon saturation revisited: temperature and compositional effects in a variety of crustal magma types. Earth Planet. Sci. Lett. 64, 295–304.
0.60
LnDZr(Zir/Liq) = -3,8 – [0,85.(M-1)]-12900/T750
500
250
00.80 1.00 1.20
930°C
860°C
800°C
750°C PERALKALINEPERALUMINOUS
ZIRCON SOLUBILITY IN SILICATE MELTS
METALUMINOUS
U - Th FRACTIONATION IN THE3 TYPES OF U – RICH ACIDIC MAGMAS
Peralkaline Peraluminous Metaluminous
graniteAv.
graniteAv.
graniteAv.
U (ppm)
Th (p
pm)
Complex U-Th-REE minerals
� Peralkaline complexes
� Carbonatites (Palaborwa, South Africa)
� Intrusive U deposits (IAEA classif.) Porphyry Cu
(high-K calc-alkaline granites)
U deposits related to crystal fractionation
EVOLUTION Of U-FRACTIONATIONDURING EARTH HISTORY
4 major periods :
1 : 4.6 – 3.2 Ga2 : 3.2 – 2.2 Ga3 : 2.2 – 0.4 Ga
4 : 0.45 - present
4.6 3.2 00.452.2
HADEAN ARCHEAN PROTEROZOIC PALEOZOIC
EVOLUTION Of U-GEOCHEMISTRYDURING EARTH HISTORY
14.6-3.2 Ga : HADEAN - PALEOARCHEAN
- thin mafic crust created by :
- Primitive mantle melting (7-21 ppb U)� basalts � TTG melts from partial melting of basalts
� Moderate magmatic U enrichments (few ppm in TTG)
� No or weak subduction processes
� Anoxic atmosphere
NO URANIUM DEPOSITS
magmatic differentiation+
mantle partial melting
Mantle
< 3.2 Ga 2.2 Ga 2.0 1.8 1.5
primitive
basaltsmagmatic differentiation
+basalt
partial melting
TTG
U < 1-2 ppm
EVOLUTION Of U-GEOCHEMISTRY DURING EARTH HISTORY : 1< 3.2 Ga : EARLY ARCHEAN
U(IV) U(VI)
magmaticdifferentiation
+mantle
partial melting
metasomatizedmantle
Subduction: oceanic crust
Singhbum Closepet …
U richcalc-alkaline
magmas
U richcalc-alkaline
magmas
KaapvalHigh-K granites
Start of subduction:recycling of
U-Th-K-rich crust materialstronger magmatic enrichment :
first K-U-Th granites
3.2 Ga 2.2 Ga 2.0 1.8 1.5
EVOLUTION Of U-GEOCHEMISTRY DURING EARTH HISTORY : 23.2-2.2 Ga : ARCHEAN & Upper PALEOPRO.
U(IV)
U-richperaluminous
magmas
Crust partialmelting
Tanco
pegm.
2.6 Ga2.8 Ga
PRE-3.1 Ga GRANITES - WITWATERSRAND BASIN (S.A.)
Intracratonic basin Large fluvio-deltaic
systems
3.09 < dep. < 2.7 Ga
Metamorphic peak : 2-3 kbar - 350 °C
Witwatersrand Basin South Africa
Frimmel, Earth-Sci Rev 70 (2005) 1–46
3A12.2-2.0 Gahigh pO2
uranyl ion [UO2]2+ in solution
U rich precursors :Organic-rich shelf sediments,
phosphorites
First chemical deposit(redox controlled) :
Oklo (Gabon) at 2.0 Ga
magmatic differentiation+
mantle partial melting
metasomatized
Mantle
Erosion-alterationin anoxic conditions
Subduction:oceanic crust +
sediments
Singhbum Closepet
GOE
Paleoproterozoicpassive margin
sediments
U-richperaluminous
magmas
Witwatersrand– Elliot Lake
Oklo
Uraninitedeposits in
quartz-pebbleconglomerate
U richcalc-alkaline
magmas
KaapvalHigh-K granites
Tanco
pegm.
U richcalc-alkaline
magmas
3.2 Ga 2.2 Ga 2.0 1.8 1.5
EVOLUTION Of U-GEOCHEMISTRY
DURING EARTH HISTORY
Oligomictic pebbly quartz arenite (reef), Vaal Reef, Stilfontein mine, Klerksdorp gold field1 cm
Minter, 2005
EVIDENCES FOR A REDUCED ATMOSPHERE < 2.3 Ga
2.2 Ga
Age distribution of banded iron-formations (after James, 1983), pyritic quartz-pebble conglomerates, continental red-bed sediments
Late Archean evolution (2.8 – 2.5 Ga)- rapid growth of the continents,
- decrease in mantle heat flux
� diminished outgassing of reduced species,
-proliferation of stromatolites
� large increase in O2-producing photosynthesis
- large-scale burial of organic matter in continental shelves
Higher O2 production, lesser O2 demand from sinks (red. gases, org. mat.)
� increased net supply of O2 to the atmosphere–hydrosphere
� CO2 drawdown due to large-scale carbonate platforms
Increase of : � pO2 in the atmosphere and pH of the hydrosphere
ARCHEAN ATMOSPHERECOMPOSITION
EVOLUTIONtwo theories :
• (A) ReducingpO2 (a) Kasting (1987, 2001)
(b) Rye & Holland (2000) others Pavlov et al. (2001a)
Kasting (2001)
(B) Oxidising(Ohmoto, 2004)
EVOLUTION Of U-GEOCHEMISTRYDURING EARTH HISTORY
3
2.2-0.45 Ga
high pO2 , uranyle ion [UO2]2+ -> in solution
3A12.2-2.0 Gahigh pO2
uranyl ion [UO2]2+ in solution
U rich precursors :Organic-rich shelf sediments,
phosphorites
First chemical deposit(redox controlled) :
Oklo (Gabon) at 2.0 Ga
magmatic differentiation+
mantle partial melting
metasomatized
Mantle
Erosion-alterationin anoxic conditions
Subduction:oceanic crust +
sediments
Kola
Singhbum Closepet
GOE
Paleoproterozoicpassive margin
sediments
U-richperaluminous
magmas
Witwatersrand– Elliot Lake
Oklo
syn-magmatic concentrations in pegmatoids
Crust partialmelting
Uraninitedeposits in
quartz-pebbleconglomerate
U richcalc-alkaline
magmas
KaapvalHigh-K granites
Tanco
pegm.
U richcalc-alkaline
magmas
3.2 Ga 2.2 Ga 2.0 1.8 1.5
EVOLUTION Of U-GEOCHEMISTRY
DURING EARTH HISTORY
Oklo - Okélobondo the first redox controlled U-depositsOklo - Okélobondo the first redox controlled U-deposits
100 m
W E
Okélobondo mine
151-2
3-67-9
13
10-16
OK84bis
FA sandstone
MineralizedC1 layer
FB black shales
ArcheanBasement
+ Reactionzones
Redox
boundary
EVOLUTION Of U-GEOCHEMISTRYDURING EARTH HISTORY
3A22.2-1.8 Ga
Oxydation of U accumulated as detrital uraninite
Huge production of organic matter �Carbon-rich shelf sediments (shungite) ; phosphorites ...
Strong U enrichment of post 2.2Ga epicontinental platform sediments :
Genesis of large U provinces : Wollaston belt (Athabasca, Canada),
Cahill Formation (N. Territory, Australia)Francevillian (Gabon)Talivaara (Finland)Shunga series (Onega Lake Russia) …
� Archean: Litsk area, NE Kola Peninsula, Russia, U pegmatoids
� “Hudsonian”s.l. (2.1-1.8 Ga): Wollaston + Mudjatik synsedimentary U enrichment : meta-arkoses (Duddridge L.), calcsilicates (Burbridge Lake & Cup L.) pegmatoids (Charlebois alaskites)
Steward Lake, Québec, CANADANorthern Québec, Ungava Bay and Baffin Island, U-pegmatoids, CANADA
Litsk district, Kola Peninsula, RUSSIA, U pegmatoids, Wheeler Basin, Colorado, USA: U- pegmatoids
Orrefjell, NORWAY: U-pegmatoidsSouthern FINLAND : Late orogenic potassic granites
Crocker Well, Olary Province, Flinders Range, South AUSTRALIASix Kangaroos area of Cloncurry-Mt. Isa District, AUSTRALIA
Nanambu, Nimbuwah, Rum Jungle complexes, Katherine-Darwin area, AUSTRALIA
� “Grenvillian” s.l. (1 Ga): Bancroft, ONTARIO : 4 mines (5,700 t U produced), Mt Laurier, Johan Beetz, Havre St Pierre, Sept Iles, Port Cartier, St Augustin QUÉBEC
�“Pan-African”: Rössing,SH,Husab,Valencia , IdaDome,Goanikontes
U-enrichment in metamorphosed epicontinental platform sediments
Shunga event huge amounts of organic matter incorporated by sediments in shelf & marginal sea environments � unprecedented increase of stromatolites at 2.05 Ga. Black shales :
� FB Formation of the Franceville basin, Gabon: up to 15 wt % OC
� Upper Zaonezhskaya Formation, Onega Lake, Russia. average : 25 wt %C over 600 m
3.35 wt %OC in average black shales
� Paleoproterozoic metasedimentary rocks metamorphosed to high grade: Wollaston belt in Saskatchewan,Canada, Cahill Formation (Northern Territory, Australia) = graphitic schist that during deformation became abundant graphite-rich fault zones (geophysical conductors)
� U content of these carbonaceous shales is anomalous, averaging 3.5 ppm to 10.8 ppm for the Francevillian, and up to 31 ppm (12−84 ppm) for the Onega basin.
� Average U content of younger black shale is also 30 ppm � indicate that by 2 Ga, oxidizing conditions were already sufficient to dissolve U as UO2+ and to deposit it in reduced environments.
Th and U analyses of shale show a significant decrease in their mean Th/U ratio from 4 at the Archean-Proterozoic boundary to 0.55 in the late Phanerozoic
Widespread deposition of black shale at 2.1 Ga related to increased weathering fluxes of nutrients such as P into the oceans triggered by global changes after major glaciations � increased availability of P have also stimulated photosynthetic O2 production
� first large phosphogenic event at 2.1 Ga in similar environments, also enriched in U (2.1 to 1.92 Ga Ludicovian epicontinental carbonaceous strata of Karelia.
Sea water became the largest U resource3.3 mg U / m3 (mg/m3= ppb)
= 4 billion t U
Exploitation technically possible, but costly :
Japanese scientists give prices > 250 $ / kg Uprobably > 1000 $ / kg to day
U in sea water(Arabian Sea)
Though dissolved O2 is low from 200 to1200 m, U concentration is uniform with depth.
No measurable change in U concentration in the water column during the seasons sampled
There is neither removal of U due to sub-oxic and denitrifying conditions nor addition of U from regeneration of biogenic particles in the intermediate waters
R. Rengarajan et al., Oceanologica Acta 26 (2003) 687–693
3.3 ppb
Example of the airborne gammaspectrometric map of Finland
The quantity of U transferred to sea water should vary
accordingly to the U contentof the eroded domains
U
U
The role of U content in the source area
IV (S) SYNSEDIMENTARY U DEPOSITS The metal is deposited within the sediments
during sedimentation processes
subdivided into 4 major types:
• IV.1 (SMs) Mechanical sorting Quartz Pebble Conglomerates (QPC)
• IV.2a (SRtm) Redox trapping in marine environments black shales.
• IV.2b (SRtc) Redox trapping in contin envir coal, lignite, peat bog, swamp
• IV.3 (SCcr) Crystal-chemical and redox trapping phosphorites
VERY LARGE LOW GRADE RESOURCES
Organic matter rich rocks & phosphorites considered as unconventional resources
� U deriving from sea water of surficial waters
IV (S) SYNSEDIMENTARY U DEPOSITS
•IV.2a (SRtm) Redox trapping in marine environments black shales
• IV.2b (SRtc) Redox trapping in contin envir coal, lignite, peat bog, swamp
Seawater only rarely becomes reducing(ex.: deep or bottom waters of the Black Sea, some fjords, Cariaco Trench)
Suboxic or anoxic conditions achieved at depth in marine sediments more frequently, in regions where there is a flux of high Corg to the seafloor as a result of high biological productivity in overlying surface water
Such areas occur most often on or near continental margins cover roughly 8% of the total area of the sea floor
U is present in seawater in the +6 state, generally as the very soluble uranyl tricarbonate species: UO2(CO3)3
-4
In reducing conditions its is reduced to the relatively insoluble U(IV)
IV.2a (SRtm) Redox trapping in marine environments black shales
U concentration in sediment and pore waters from the California
Shelf sediments
Consumption of 2.5% Corg at - 6 cm lead to suboxic conditions & reduction of U6+ to U4+
Organic-rich sediments tend to be rich in UThis reflects biological uptake of U or adsorption of
U on dead organic particles falling through the water column
This U may be released when the org. matter is remineralized in the sediment, producing high U contents in sediment pore water & consequently,
diffusion of U from sediments to seawater
On the whole, diffusion into sediments appears to be dominant
Barnes & Cochran (1990) diffusion into suboxic sediments removes 0.25 to 0.32 1010 gU/yrKlinkhammer & Palmer (1991) estimate a flux of 0.67 1010 gU/yr
Suboxic sediments are the largest sink for dissolved U in the oceans
The marine uranium budget
Sources (1010 g U/yr) Riverine Input 1
Amazon Shelf Sediments 0.14Total 1.14
Sinks (1010g U/yr) Sediments Oxic, deep sea 0.08
Metalliferous 0.14Underlying anoxic water 0.13Suboxic 0.25-0.32Corals and Molluscs 0.08
Ocean Crust Low temperature 0.23High temperature 0.04
Total 0.95-1.02
Barnes and Cochran (1990)
Mineralization ProcessLeventhal (1990), les eaux profondes euxiniques ont permis un piégeageefficace des métaux par réduction et préservation de la matière organique.Kalinowski et al. (2004): les fortes concentrations en U à Ranstad seraientdues en partie à des bactéries produisent des acides organiques à chainecourte et des ligands capables de modifier le pH et favoriser leur chélation.Teneur en matière organique pas toujours corrélée à la teneur en U.Plusieurs autres facteurs de concentration de l’U (Andersson et al, 1985) :• Importance de l’érosion de terrains granitiques riches en U situés en bordurede bassin (Harron and Associates, 2007)• existence d’un volcanisme acide avec émission de cendres, synchrone dudépôt des schistes noirs comme source additionnelle d’uranium ?• Incorporation plus efficace de l’uranium de l’eau de mer grâce au faible tauxde sédimentation par phénomènes de précipitation et adsorption.•Action biochimique de certaines algues vertes qui pourraient concentrer U
In the most enriched Upper Cambrian biozone (Peltura scarabaeoides Zone) the average concentrations of U (100 - 300 ppm)
inversely correlated to zone thicknessbed thickness variation = differences in the rate of deposition
High U levels generally found shorewards are interpreted to reflect a more vigorous bottom water circulation that promoted higher rates of mass-transfer across the sediment/ water interface relatively to the mud deposited
farther offshore. Highest levels of U (1000 - 8000 ppm) in discrete beds : KOLM
= resuspension of sediment in an anoxic water column that enhanced diffusive exchange between suspended particles and sea-
water.
Some crude oil, natural asphalt, and petroliferous rock are appreciably radioactive
U is associated with V, Ni, Cu, Co, Mo, Pb, Cr, Mn, and As.
U content of crude oil is much lower than the U content of the natural asphalt and oil extracted from petroliferous rock
U content of the ash of 78 samples ranges from 10 ppm to 10 %
U content of the total oil or asphalt ranges from less than 10 ppm to 3.24 %
Erickson, R. L., Myers, A. T., Horr, C. 1954. Association of uranium and other metals with crude oil, asphalt, and petroliferous rock. Bul. American Association of Petroleum Geologists. 38, 2200-2218
DIFFERENTS MATERIAL SOURCES IN THE SEDIMENTARY PHOSPHORITES
Shelf Margin
Phosphorites
High TOC
Mid-shelf
Fewer
Phosphorites
Low TOC
Upwellingwater
OM
Z
Hundre
ds o
f m
ete
rs
Silt-loaded continental
winds
5
Living organisms
1
1
2
4
5
Biochemical precipitation
Physical-chimical precipitation
Fluviatil particules supply
Eolian particules supply
3 42
3 Direct biological supply
6
6 Diagenetic evolution
SUBSTITUTION DANS LES SITES M
M10(ZO4)6(X)2
Ca2+ ↔ Sr2+, Mn2+, Pb2+, Ba2+, Eu2+
↔ Cd2+, Fe2+, Mg2+, Co2+, Ni2+
↔ Na+ 2M+ ↔ Ca2+ +
↔ 2M3+ + ZO44+↔ 2Ca2+PO4
3+
↔ REE3+, Y3+, Al3+ 2M3+ + ↔ 3Ca2+
↔ U4+, Th4+ M4+ + ↔ 2Ca2+
↔ U6+
The Cretaceous-Eocene Phosphate SeaU mineralization associated with phosphates are known since the PaleoproterozoicBut largest U resources with phosphates : late Cretaceous to Eocene (90-45 Ma)All deposited on carbonate platforms under the same paleolatitude (8-15º N) : S margin of Tethys Ocean: Turkey to Morocco, beyond Atlantic to Colombia & Venezuela Exceptional conditions of deposition, combining :(i) during Late Cretaceous creation of the Paleotethys Ocean : a continuous EW
seaway which merge with the Central Atlantic gulf already open during late Jurassic, by rifting of the Pangea between Laurasia and Gondwana
(ii) development of broad carbonate plateforms along S margin of the Tethys Ocean (iii) huge Late Cretaceous rise of the sea-level resulting from a global warming episode,both (i) and (ii) made possible a circum-equatorial westward oceanic current in the Tethys,
(iii) location of the Tethys at low latitudes, with the warmest climatic conditions(iv) dominant easterly winds producing a northward Eckman offshore transport of surface
waters inducing t upwelling of cold nutrient-rich waters all along the S Tethys shelves � huge biogenic productivity.
Morocco, with geological U resources of about 6.9 million tons U @ 50 - 150 ppm : ¾ of the world U resources associated with phosphates.
URANIUM CONTENT IN PHOSPHATES
URANIUM up to x100 ppm
In the apatite structure & inclusions
+ U minerals
Mean upper crust = 2,7 ppm
Recoverable during H3PO4 production
1980: 12% of world U was coming from the treatment of
phosphates
MAGMATIC APATITES
U => 3,4 %pds, Th => 15,9 %pds
D. Soudry et al. Chem. Geol.
189 (2002) 213–230
CEI S.AFRICA MOROCCO USA SENEGAL TOGORussia*Phalaborwa* Khouribga Florida
% Apatite 84 80 73 75 80 80
P2O5 38.9 36.8 33.4 34.3 36.7 36.7
CaO 50.5 52.1 50.6 49.8 50.0 51.2
SiO2 1.1 2.6 1.9 3.7 5.0 4.5
F 3.3 2.2 4.0 3.9 3.7 3.8
CO2 0.2 3.5 4.5 3.1 1.8 1.6
Al2O3 0.4 0.2 0.4 1.1 1.1 1.0
Fe2O3 0.3 0.3 0.2 1.1 0.9 1.0
MgO 0.1 1.1 0.3 0.3 0.1 0.1
Na2O 0.4 0.1 0.7 0.5 0.3 0.2
K2O 0.5 0.1 0.1 0.1 0.1 0.1
Organ. C 0.1 0.1 0.3 0.2 0.4 0.1
SO3 0.1 0.2 1.6 0.1 0.3
REE (ppm) 6,200 4,800 900 600
U3O8 11 134 185 101 124
As 10 13 13 11 18 12
Cd 1.2 1.3 15 9 53 53
Cr 19 1 200 60 6
Cu 37 102 40 13
Hg 33 0.1 0.1 0.02 0.2 0.6
Pb 11 10 17 5
Zn 20 6 200-400 www.efma.org/documents/
The uranium from unconventional resources results:
� Either SYN-MAGMATIC : concentration of U in residual melt by extreme fractional crystallization (peralkaline complexes and highly fractionated calc-alkaline granites)
� Or SYN-SEDIMENTARY : trapping mostly from sea water(sea water, blacks shales, phosphorites …) but also to a lesserdegree from surficial waters (coal, lignite, peat bogs …)
� Monazite placers
CONCLUSIONS