Parameters controlling the formation of uranium deposits associated to

sedimentary environments

Michel CUNEY

UNIVERSITE DE LORRAINE – GEORESSOURCES CREGU – CNRS

Parameters controlling the formation of U deposits associated

to sedimentary environmentsOutline

:

- Sediment related U-deposits in the IAEA classification (2012)

- Sediment related U-deposits in a genetic classification

- Main parameters controlling U deposit formation in sedimentary environments

- Mechanical sorting => Qz pebble conglomerates

- Adsorbtion + Intrinsic Redox => Black shales

- Intrinsic Redox + Crystal-chemical control => Phosphates

- Intrinsic or Extrinsic or BSR Redox + Porosity/Permeability + Volc ash ± Fault=> Intraformational redox control and Intraformational meteoric water infiltration

- Intrinsic or Extrinsic Redox + Evaporates + Faulting + Dissolution breccias=> Basin Basement redox control : unconformity related deposits

- Extrinsic Redox ? + Dissolution breccias=> Dissolution Collapse Breccia pipes

1. Intrusive 2. Granite-related 3. Polymetallic iron-oxide breccia complex 4. Volcanic-related 5. Metasomatite 6. Metamorphite 7. Proterozoic unconformity 8. Collapse-breccia pipe 9. Sandstone

10. Paleo-quartz-pebble conglomerate 11. Surficial 12. Lignite and coal 13. Carbonate 14. Phosphate 15. Black shale

Sediment related U-deposits in the IAEA classification (2012)

U deposits

types

associated to

sedimentary

basins

9. Sandstone 6152. Granite-related 128

4. Volcanic-related 117

6. Metamorphite 106

7. Proterozoic unconformity 841. Intrusive anatectic - plutonic 81

5. Metasomatite 74

11. Surficial 6610. Paleo-quartz pebble conglomerate 6212. Coal-lignite 3214. Phosphate 4115. Black shales 438. Collapse breccia pipe 16

3. Polymetallic hematite breccia complex 12

13. Carbonate 8

Number of deposits by type

METAMORPHIC

ROCKS

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

METAMORPHIC

ROCKS

M A N T L E

T °C

100100

200

300

400

600

25

800

Primitive Mantle : 21ppb

Carb. chondrites : 7ppb

Calcretes/Lignite/Coal

PhosphatesBlack Shales

Conglomerates

RollfrontBasal

Breccia

TabularTectonolithologic

Unconformity

Pipes

HTMetamorphic

Na-metasomatism

LTMetamorphic

SEDIMENTARY

ROCKS

IGNEOUS

ROCKS

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

Sediment related U-deposits in a genetic classification (i)� 1 – Fractional crystallization: Ilimausacq, Bokan Mountain

� 2 – Partial melting: Rössing

� 3 – Hydrothermal high level post-orogenic :� 3A – Volcanic - hydrothermal (Streltsovska)

� 3B – Granitic - hydrothermal (French Variscan, Erzgebirge)

�4 – Diagenetic hydrothermal systems:�4A: Intraformational redox control

�4A1: Tabular: Grants Mineral Belt, Bevereley Hills

�4A2: Tectonolithologic: Akouta, Niger

�4A3 : Karsts (beccia pipes): Colorado

�4B: Basin/basement redox control (unconformity related)

�4C: Interformational redox control (Oklo, Gabon)

� 5 - Hydrothermal metamorphic: Shinkolobwe, Mistamisk

� 6 – Hydrothermal metasomatic: � 6A – Alkali-metasomatism : Lagoa Real, Krivoi Rog

� 6B – Skarns :Mary Katheleen - Tranomaro (Madagascar)

� 7 – Syn-sedimentary:� 7A: Mechanical sorting: Qz pebble conglomerates: Witwatersrand, Elliot L.

� 7B: Redox trapping: black shales, Alum shales Sweden (marine & cont.)

� 7C: Crystal-chemical/redox trapping: phosphates : Maroc

� 8 - Intraformational meteoric fluid infiltration� 8A: Sealed paleovalleys: Vitim (Transbaikalia)

� 8B: Roll fronts: Powder River Basin (Wyoming)

� 9 - Weathering & evapotranspiration: calcretes: Yeleerie

� 10 – Other types : breccia complex (Olympic Dam)

Sediment related U-deposits in a genetic classification (ii)

Main parameters controlling U deposit formation

in sedimentary environments1 - Mechanical sorting2 - Adsorbtion3 - Redox - 3A Intrinsic

- 3B Extrinsic- 3C BSR

4 - Porosity/Permeability5 - Volcanic ash6 - Crystal-chemical control 7 - Evaporates8 - Evapo-transpiration9 - Faulting10 - Dissolution breccias : - 10A in sandstone,

- 10B in limestone

Main parameters controlling U deposit formation in sedimentary environments

1 - Mechanical sorting7 - Syn-sedimentary deposits

DEFINITION: metal deposited within the sediments during sedimentation processes

7A: Qz pebble conglomerates: Witwatersrand, Elliot Lake

VERY LARGE LOW GRADE RESOURCES

Unconventional resources

IAEA 2014 <USD 80/kgU <USD 130/kgU <USD 180/kgU

Reasonably Assured Res. (t U) 113 034 169 536 231 303

Inferred Resources (t U) 79 786 114 429 168 283

TOTAL 399 586

THREE GENETIC HYPOTHESES

(i) Anoxic atmosphere :

a) Placer Uraninite trapped between pebbles comprising gravel bars

in braided rivers, concentrated by mechanical processes

on erosion surfaces, particularly along the unconformities

b) Modified placer

(ii) Hydrothermal : oxic atmospherealteration assemblage: sericite-chlorite-pyrophyllite-chloritoid

Elliot Lake, Ontario, CanadaΣREE = 16 370 ppmΣHREE/ΣLREE = 0.87

Dominion Reef - South AfricaΣREE = 28 771 ppmΣHREE/ΣLREE = 0.77

Magmatic REE signature of detrital uraninites

100 µm BSEPhD thesis, Duhamel, 2009

Puruvesi, Karelia, FinlandΣREE = 15 669 ppmΣHREE/ΣLREE = 0.53

Cigar Lake, Athabasca, Canada, Bonhoure, 2007

ΣREE = 1 766 ppmΣHREE/ΣLREE = 2.18

REE signature of magmatic / hydrothermal uraninites

Polyarnoe (Kola-Russia)ΣREE = 22 889 ppmΣHREE/ΣLREE = 0.30

PhD thesis, Duhamel, 2009 PhD thesis, Duhamel, 2009

Main parameters controlling U deposit formation in

sedimentary environments

2 - Adsorbtion + 3A Intrinsic Redox

7 - Syn-sedimentary depositsDEFINITION: metal deposited within the sediments during sedimentation processes

� 7B: Redox trapping (marine & continental) : black shales,

Alum shales Sweden, coal, peat bogs, …

VERY LARGE LOW GRADE RESOURCES

Unconventional resources

No resources reported in Red Book 2014, but resource potential of millions t U

7 - Syn-sedimentary deposits7B: redox trapping (marine & continental)

best example

Cambrian U-rich

Alum Shales in Sweden

mU = 100 - 300 ppm

Upper Cambrian biozone is the richest

� reversely correlated to the rate of deposition

High U levels generally found shorewards:

Highest U levels (1000-8000 ppm) in KOLM beds

Recent exploration frontiers (Central Sweden)

Main parameters controlling U deposit formation in

sedimentary environments

Intrinsic Redox + Crystal-chemical control

7C: PhosphoritesU production: 690 tU in Belgium (1975-1999) Morocco phosphates

17 150 tU in the USA (1954 - 1992) Florida phosphates

40 000 tU Kazakhstan, marine organic deposits (fish bones)

« Brazil: Feasability project for the ITATAIAdeposit from collophanite »

RESOURCESMarine phosphates are generally anomalous in U : x 10 to x 100 ppm U

Tunisia : 50 - 60ppm U Morocoo : 150ppm U (locally 600 ppm)

Resources = 15 millions tons U (Africa: 8.5 millions)

Morocoo : 7 millions t U @ 155 ppm U

URANIUM IN PHOSPHORITTES

URANIUM dominantly In the structure of apatite �

Crystal-chemical control + redox :U(IV) mainly in the structure

D. Soudry et al. Chem. Geol.

189 (2002) 213–230

Main parameters controlling U deposit formation in

sedimentary environments

Intrinsic or Extrinsic or BSR Redox + Porosity/ Permeability + Volcanic ash ± Fault

4 - U deposits related to diagenetic hydrothermal systems4A: Intraformational redox control

4A1: Tabular: Grants Mineral Belt, Beverley

4A2: Tectonolithologic: Akouta, Niger

8 - Intraformational meteoric fluid infiltration8A: Sealed paleovalleys: Vitim (Transbaikalia)

8B: Roll fronts: Powder River Basin (Wyoming)IAEA 2014 (sandstones) <USD 80/kgU <USD 130/kgU <USD 260/kgU

Reasonably Assured Res. (t U) 511 153 1 165 707 1 467 697

Inferred Resources (t U) 425 668 743 333 921 467

TOTAL 2 389 164 t U

8 - Intraformational meteoric fluid infiltration8B: Roll fronts: Powder River Basin (Wyoming)

VERY LARGE LOW GRADE RESOURCES

Roll front deposits

resulting from

extrinsic reductants fault controlled influx of

reduced fluids(South Texas)

Reduced

sandstone Reduced

sandstone

roll front

limb

Extend of

upward

gas migration

Extend of

downward

gas migration

Oxygenated meteoric ground waters

H2S

Hydrocarbons

Adams and Smith, 1981

Primary

oxidized

sandstone

Bacterial Sulfate Reduction in the genesis of a roll front type deposit Erlian Basin, China

Bonnetti et al., 2015

SRB-related secondary reduction model (H2S-reducing barrier)

Ningyoite

Phytoclast

Coffinite

Phytoclast

PyPy

Fe/Ti

Oxide

Py

Py

U-rich

Fe/Ti

Oxide

Phytoclast

Fe/Ti

Oxide

Hem

Py oxidation & U leaching

U mineralization on Py & OM

U preconcentration

SRB Zone

U with

organic

matter

Bonnetti et al., 2015

4 - U deposits related to diagenetic hydrothermal systems4A: Intraformational redox control

EVIDENCES OF VOLCANIC CONTRIBUTION IN THE TIM MERSOI BASIN

ANALCIME

ANALCIME

Melt inclusion geochemistry from sandstone

Al/(Na+K+2Ca) in cations

U content of the melts

10-20 ppm U

Peralcaline

PeraluminousMetaluminous

Al/(

Na+

K)

Limit of volcanic ash

deposition of the NW

USA compared with

the map of the

annular complexes of

Niger and Nigeria

d’après Forbes, 1989, modifié

U deposit

model for the

Akouta area

deposits

Diagenetic fluids

100-140°C

12-15 wt% NaCl

Main parameters controlling U deposit formation in

sedimentary environments

3A Intrinsic or 3B Extrinsic Redox + 8 - Evaporates + 10 – Faulting + 11 - Dissolution breccias

4 U deposits related to diagenetic hydrothermal systems:

Large – High grade Resources

Reasonably assured resources <USD 80/kgU <USD 130/kgU <USD 260/kgU

318 917 463 272 569 120

Inferred resources 92 150 166 873 195 607

TOTAL 764 727

1 1dolomitizationCa <=> Mg

○○○○○

○○○○○○

○○○○○○

○○○○○

2Na brine 3a

3b3c

4

5-6

km

EVAPORITES ?

Basin/basement

Redox

boundary

Diagenetic brines

150-200°C

30-35 % eq NaCl

Conceptual fluid percolation model for Basin/Basement redox control

(Unconformity related deposits)

Diagenetic brines, 150-200°C, 30-35 % eq NaCl

Element concentrations for NaCl-rich & CaCl2-rich brines (LA-ICP-MS)

Richard et al., 2015

U(VI) solubility in H2O–NaCl fluids (155 °C) relative to pH & Na content

Richard et al., Nature 2011

DEPOSITS RELATED TO HYDROTHERMAL FLUIDS(HD) hydrothermal-diagenetic• (HDIa) with intraformational redox control:• (HDBb) with basement / basin redox control

• (HDIr) interformational redox boundary

•

100 m

W E

Okélobondo mine

151-2

3-67-9

13

10-16

OK84bis

FA sandstone

Mineralized

C1 layer

FB black shales

Archean

Basemen

t

+ Reaction

zones

Diagenetic fluids : same T, same salinities as unconformity related deposits

Interformational

Redox

boundary

Main parameters controlling U deposit formation

in sedimentary environments

3B Extrinsic Redox ? + 11B - Dissolution breccias in limestone

4 – Diagenetic hydrothermal systems:4C: Intraformational redox control

4C3: Dissolution Collapse Breccia pipes

Reasonably assured resources <USD 80/kgU <USD 130/kgU <USD 260/kgU

400 400 400

Inferred resources 18 600 18 600 18 600

TOTAL 19 000 t U

Small – High grade Resources

Ore-forming fluids

= diagenetic brines

have deposited sphalerite, calcite & dolomite:

� temperatures: 80°C to 173°C

� salinities >9 wt. % eqv. NaCl

most commonly >18 wt. % eqv. NaCl

Similar to Mississippi Valley-type deposits

TIBORLIA

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