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1 u deposits sandstones looking forward cuney

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Austria conference 2012-Uranium Sandstone

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1 u deposits sandstones looking forward cuney

  1. 1. Sandstone uranium deposits: Looking forward Michel CUNEY UMR G2R – CREGU – CNRS Vandoeuvre les NANCY
  2. 2. PRESENTATION HIGHLIGHTS To propose a general framework for the different types of uranium depositsassociated with sandstone within the continuum of the geologic cycle To try to go beyond the usual classifications using the recent work of the UDEPOgroup and more personal viewsSuch a general framework should help to set up the different contributions whichwill be presented during this meeting concerning deposits from all over the world To trace the avenues for future research and exploration of sandstone relateddeposits
  3. 3. IAEA classification 20121. Intrusive2. Granite-related3. Polymetallic iron-oxide breccia complex4. Volcanic-related5. Metasomatite6. Metamorphite7. Proterozoic unconformity: 82 deposits8. Collapse-breccia pipe (Arizona Strip, USA)9. Sandstone: 576 deposits from 1405 compiled in the UDEPO data base10. Paleo-quartz-pebble conglomerate: 62 deposits11. Surficial: 60 deposits12. Lignite and coal13. Carbonate14. Phosphate15. Black shale
  4. 4. IAEA classification 20129. Sandstone9.1. Basal channel(Dalmatovskoye, Russian Federation; Beverley, Australia)9.2. TabularContinental fluvial, U associated with intrinsic reductant (Arlit type, Niger)Continental fluvial, U associated with extrinsic humate/bitumen (Grants type, USA)Continental fluvial vanadium-uranium (Salt Wash type, USA)9.3. RollfrontContinental basin, U associated with intrinsic reductant (Wyoming type, USA)Continental to marginal marine, U associated with intrinsic reductant (Chu-Saryisu type, Kazhakstan)Marginal marine, U associated with extrinsic reductant (South Texas, USA)9.4. Tectonic-lithologic(Lodève Basin, France; Franceville Basin, Gabon)9.5. Mafic dykes/sills in Proterozoic sandstone(Westmoreland District, Australia; Matoush, Canada)
  5. 5. A GENETIC CLASSIFICATION OF U-DEPOSITS Cuney, 2012 1 – Fractional crystallization 2 – Partial melting 3 – Hydrothermal high level post-orogenic :  3A – Volcanic - hydrothermal  3B – Granitic - hydrothermal 4 – Diagenetic hydrothermal systems:  4C: Intraformational redox control 4C1: Tabular: Grants Mineral Belt, Beverley 4C2: Tectonolithologic: Akouta, Niger 4C3 : Karsts (breccia pipes): Colorado  4A: Basin/basement redox control (unconformity related)  4B: Interformational redox control (Oklo Gabon) but fluids similar to unconf. related U 5 - Hydrothermal metamorphic (Katanga deposits transitional with diagenetic hydrothermal systems)
  6. 6. A GENETIC CLASSIFICATION OF U-DEPOSITS Cuney, 2012 6 – Hydrothermal metasomatic:  6A – Alkali-metasomatism  6B – Skarns :Mary Katheleen 7 – Syn-sedimentary:  7A: Mechanical sorting: Qz pebble conglomerates  7B: Redox trapping: black shales  7C: Crystal-chemical/redox trapping: phosphates 8 - Intraformational meteoric fluid infiltration  8A: Sealed paleovalleys: Vitim (Transbaikalia)  8B: Roll fronts: Powder River Basin (Wyoming) 9 –- Weathering & evapotranspiration: calcretes 10 – Other types
  7. 7. U deposits related Calcretes /Lignite/Coal U deposits related to magmatic SURFACE WATERS to sedimentary Meteoric / Sea Conglomerates rocks Volcanic Phosphates basins IOCG(U) N Black shales O Basal Sandstone SI Ground Fract. cryst. Veins T EN waters Rollfront hosted Magmatic- Fluid EX DI Hydrothermal MIXING AG Tabular Tabular Fluids EN Formation ES waters Tectonolithol - IS . Breccia Pipes N IO MAGMATIC FRACTIONATION DIAGENETIC ATMAGMATIC M HU FLUIDS FLUIDS EX GEOLOGIC CYCLE Unconformity CO CO L LL Crustal Metamorphic L.T. IIS SII M Metamorphic Skarns Skarns IS ON ON PH fluids Na-metasomatism - Alaskites Alaskites Silicate M OR Metamorphic H.T. Crust partial Partial melts TA melting Melting MIX I ME U deposits related NG Subduction fluids to metamorphism N Mantle TIO melting melting MANTLE UC BD MELTS / FLUIDS SU
  8. 8. IAEA classification 20129. Sandstone9.1. Basal channel(Dalmatovskoye, Russian Federation; Beverley, Australia)9.2. TabularContinental fluvial, U associated with intrinsic reductant (Arlit type, Niger)Continental fluvial, U associated with extrinsic humate/bitumen (Grants type, USA)Continental fluvial vanadium-uranium (Salt Wash type, USA)9.3. RollfrontContinental basin, U associated with intrinsic reductant (Wyoming type, USA)Continental to marginal marine, U associated with intrinsic reductant (Chu-Saryisu type, Kazhakstan)Marginal marine, U associated with extrinsic reductant (South Texas, USA)9.4. Tectonic-lithologic(Lodève Basin, France; Franceville Basin, Gabon)9.5. Mafic dykes/sills in Proterozoic sandstone(Westmoreland District, Australia; Matoush, Canada)
  9. 9. 9.1. Basal channel (Paleovalley): Vitim district, Russian Federation: RAR: 52,000 mt U, Speculative R.: 100,000 mt U8 deposits over 250km2 with 44,800mtU @ 0.05-0.3 %U, prognosticated R.: 60,000mt U, Khiagda: 15,500 mt UPaleochannels with up to 50 m thick Oligocene-Miocene colluvial to alluvial grey to multicoloredcarbonaceous clay-siltstone, sandstone, conglomerate, intercalated lignite seams. Pyrite and plant debris, ~0.8% CorgGeological map of the Khiagda ore field
  10. 10. 9.1. Basal channelTypical cross-section through the Khiagda deposit. SW 60 km NE 0 0 30 basalt 60 U ore granite 90 m Neogene sediments (sand, silt, clay) grey oxidized reduced Source: Highly potassic calcalkaline Hercynian granites Transport: infiltrated meteoric fluids through permeable siliciclastic rocks Deposition: reduction by detrital organic matter (20 Ma to present)
  11. 11. IAEA classification 20129. Sandstone9.1. Basal channel(Dalmatovskoye, Russian Federation; Beverley, Australia)9.2. TabularContinental fluvial, U associated with intrinsic reductant (Arlit type, Niger)Continental fluvial, U associated with extrinsic humate/bitumen (Grants type, USA)Continental fluvial vanadium-uranium (Salt Wash type, USA)9.3. RollfrontContinental basin, U associated with intrinsic reductant (Wyoming type, USA)Continental to marginal marine, U associated with intrinsic reductant (Chu-Saryisu type, Kazhakstan)Marginal marine, U associated with extrinsic reductant (South Texas, USA)9.4. Tectonic-lithologic(Lodève Basin, France; Franceville Basin, Gabon)9.5. Mafic dykes/sills in Proterozoic sandstone(Westmoreland District, Australia; Matoush, Canada)
  12. 12. 9.1. Basal channel looking forward Model mainly discovered in Russia with some other minor occurrences in NWMongolia and Canada (Blizzard) Not considered as a major exploration target in other countries.Should exist in other part of the world where valleys incized in U-rich granites,filled with organic matter bearing silicicalstic sediments, covered by basalts Interesting features : • Close to the surface • Amenable by in situ leaching • Average size and grades
  13. 13. 9.2. Tabular U disseminated within reduced sediments along lenticular shaped massesoriented parallel to the stratigraphy Individual deposits: x100 t U up to 150,000 t U, @ 0.05 - 0.5% (up to 1%) 3 sub-types :Continental fluvial, U associated with intrinsic reductant Arlit type, NigerContinental fluvial, U associated with extrinsic humate/bitumen Grants type, USAContinental fluvial vanadium-uranium Salt Wash type, USA
  14. 14. 9.2. TabularContinental fluvial, U associated with intrinsic reductant Tabular to lenticular U ore bodies hosted in arkoses rich in detrital C-matter incontinental fluvial channel systems, interbedded with claystone-shale beds. U ± Zn, Cu, V, Mo, Zr: pitchblende & coffinite disseminated in reduced, pyriticsandstone and as finely disseminated argillic-organic U complexes Resources are small to large (< 100 to 150 000 t) @ 0.10 to 0.50%Ex. : Arlit District (Niger) with total resources exceeding 600 000 t.
  15. 15. 9.2. TabularContinental fluvial, U associated with extrinsic humate/bitumenU associated with humate/bitumen Mineralization disseminated in lenses within continental sandstone intercalatedwith shale Sandstone represents 60-80% of the volume and but pyroclastics are common The host sandstone was deposited in a mid-fan environment within an extensivefluvial-lacustrine sedimentary systemResources are medium to large (500-35,000 t @ 0.10-0.40%) Ex.: Ambrosia Lake District (USA) with resources in the order of 130 000 t U
  16. 16. 9.2. TabularContinental fluvial, U associated with extrinsic humate/bitumen The primary ore (reduced ore which has undergone little alteration since its formation during early diagenesis) = fine-grained mixture of urano-organic complexes : = cryptocrystalline colfinite + amorphous organic matter that commonly fills primary pores Amorphous organic matter highly aromatic: high O/C ratio: 0.2 - 0.3 originated as humic acids derived from plant material  However, irradiation of organic matter (OM) leads to its oxidation Are the O/C ratios determined during the 80’s those of the pristineOM or do they correspond to modified migrated OM from marine origin ?
  17. 17. 9.2. TabularContinental fluvial vanadium-uranium U associated with V in reduced fluvial sandstone within a sequence ofcontinental red-bed sediments. The sedimentary succession comprises: * thin, widespread units of reduced sandstone * with interbeds of grey clay and carbonaceous debris U ore is largely epigenetic, but syngenetic uranium enrichment may have existedDeposits are small to medium (1-2 000 t U) @ 0.05-0.50% UHigh vanadium content often increases their economic viability Ex : Salt Wash uranium district, USA
  18. 18. IAEA classification 20129. Sandstone9.1. Basal channel(Dalmatovskoye, Russian Federation; Beverley, Australia)9.2. TabularContinental fluvial, U associated with intrinsic reductant (Arlit type, Niger)Continental fluvial, U associated with extrinsic humate/bitumen (Grants type, USA)Continental fluvial vanadium-uranium (Salt Wash type, USA)9.3. RollfrontContinental basin, U associated with intrinsic reductant (Wyoming type, USA)Continental to marginal marine, U associated with intrinsic reductant (Chu-Saryisu type, Kazhakstan)Marginal marine, U associated with extrinsic reductant (South Texas, USA)9.4. Tectonic-lithologic(Lodève Basin, France; Franceville Basin, Gabon)9.5. Mafic dykes/sills in Proterozoic sandstone(Westmoreland District, Australia; Matoush, Canada)
  19. 19. 9.3. Rollfront mineralized zones are crescent shape, oriented down the hydrologic gradientdiffuse boundaries with reduced sandstone on the down-gradient side . …sharp contacts with oxidized sandstone on the up-gradient side elongated and sinuous mineralized zones approximately parallel to the strike, . . . perpendicular to the direction of deposition and groundwater flow Resources from x 100 to X 1,000 t U @ 0.05% to 0.25%Continental basin, U associated with intrinsic reductant Wyoming type, USAContinental to marginal marine, U associated with intrinsic reductant Chu-Saryisu type, KazhakstanMarginal marine, U associated with extrinsic reductant South Texas, USA
  20. 20. 9.3. Rollfront U deposit genesisFormed where oxidized groundwater encounters reducing conditions in permeable sandstone U in solution is precipitated at the redox interface, forming a crescent- shaped roll-front ore body The roll front crosscut the sandstone bedding The reduction front migrates gradually in the direction of groundwater flow, creating the ore body with progressive U-accumulation
  21. 21. Se U, V MoZonality with Se behindthe front and Mo beyond U and V
  22. 22. 9.3. RollfrontContinental basin, U associated with intrinsic reductant U occurs disseminated at the redox boundary at the contact with pyrite-bearingsandstone and detrital carbonaceous debris on the down-gradient side in arkosicand subarkosic sandstones deposited in intracratonic or intermontane basins These basins are in spatial proximity with proximal to rocks (such as granites,and tuffs) containing anomalous uranium concentrations Most deposits occur within interbedded sequences of fluvial sandstones andvolcanic-rich sediments The shapes of deposits is strongly controlled by the permeability of the hostrocksResources are small to large (100-1 000 t U @ 0.05-0.20%)Ex.: Wyoming basins with resources of 250 000 t.
  23. 23. 9.3. RollfrontContinental to marginal marine, U associated with intrinsic reductant Deposits are similar to roll front deposits in continental basins, but hostlithologies correspond to a sequence of mixed continental and marginal marineorigin. Resources are medium to large (1 000-100 000 t U @ 0.04-0.08% U)The World’s largest resources of this type (> 800 000 t) are located in the Chu-Sarysuand Syr-Daria Basins (South Kazakhstan).
  24. 24. Evolution of Kazak Uranium Production 19.450 t U 35% World P.
  25. 25. 9.3. RollfrontMarginal marine, U associated with extrinsic reductant U is concentrated in roll-type deposits near faults and in contact with pyrite /marcasite-bearing sandstone on their downgradient side Hosts environment include point bars, lateral bars and crevasse splaysdeposited in a fluvial environment and barrier bars and offshore bars in a marineenvironment Deposits are small to medium (50-5 000 t U @ < 0.05-0.25% U)Ex.: South Texas Uranium region : resources of 100 000 t U
  26. 26. Oxygenated meteoric ground waters Adams and Smith, 1981 limb Extend of upward roll front gas migration Reduced sandstone Reduced gas mi sandstone gra t ion Primary oxidized sandstone(iii) fault controlled influx of reducing compounds Extend of downward (South Texas) H2S gas migration Hydrocarbons
  27. 27. IAEA classification 20129. Sandstone9.1. Basal channel(Dalmatovskoye, Russian Federation; Beverley, Australia)9.2. TabularContinental fluvial, U associated with intrinsic reductant (Arlit type, Niger)Continental fluvial, U associated with extrinsic humate/bitumen (Grants type, USA)Continental fluvial vanadium-uranium (Salt Wash type, USA)9.3. RollfrontContinental basin, U associated with intrinsic reductant (Wyoming type, USA)Continental to marginal marine, U associated with intrinsic reductant (Chu-Saryisu type, Kazhakstan)Marginal marine, U associated with extrinsic reductant (South Texas, USA)9.4. Tectonic-lithologic(Lodève Basin, France; Franceville Basin, Gabon)9.5. Mafic dykes/sills in Proterozoic sandstone(Westmoreland District, Australia; Matoush, Canada)
  28. 28. 9.4. Tectonic-lithologicdiscordant to concordant to strata. Occur in permeable fault zones and adjacent sandstone beds in reducingenvironments created by hydrocarbons and/or detrital organic matterUranium is precipitated in open fracture or fault zones related to tectonicextension.Individual deposits contain a x 100 mt U up to 5 000 mt U @ 0.1%- to 0.5%.Ex. : Lodève District (France) and the Franceville Basin (Gabon).
  29. 29. 9.4. Tectonic-lithologicGeological cross-section of the north border of the Lodève Permian Basin (FRANCE)The U mineralization is associated to the main fault systems (from Mathis et al. 1990)
  30. 30. IAEA classification 20129. Sandstone9.1. Basal channel(Dalmatovskoye, Russian Federation; Beverley, Australia)9.2. TabularContinental fluvial, U associated with intrinsic reductant (Arlit type, Niger)Continental fluvial, U associated with extrinsic humate/bitumen (Grants type, USA)Continental fluvial vanadium-uranium (Salt Wash type, USA)9.3. RollfrontContinental basin, U associated with intrinsic reductant (Wyoming type, USA)Continental to marginal marine, U associated with intrinsic reductant (Chu-Saryisu type, Kazhakstan)Marginal marine, U associated with extrinsic reductant (South Texas, USA)9.4. Tectonic-lithologic(Lodève Basin, France; Franceville Basin, Gabon)9.5. Mafic dykes/sills in Proterozoic sandstone(Westmoreland District, Australia; Matoush, Canada)
  31. 31. 9.5. Mafic dykes/sills in Proterozoic sandstonemineralization is associated with mafic dykes and sills that are interlayered withor crosscut Proterozoic sandstone formations Deposits can be subvertical along the dyke’s borders, sometime within the dykes,or stratabound within the sandstones along lithological contacts (WestmorelandDistrict, Australia; Matoush, Canada).Deposits are small to medium (300-10 000 t U @ 0.05-0.40% U)Ex.: Westmoreland District, Australia; Matoush, Canada
  32. 32. 9.5. Mafic dykes/sills in Proterozoic sandstone Type 1 Type 2 Mafic volcanics sandstone Type 3 Type 4 Mafic Volcanics Felsic Volcanics Unconformity Proterozoic sandstone Uranium mineralization 0 40 m Geological setting and types of mineral occurrences in the Westmoreland U field
  33. 33. Relationships between sandstoneuranium deposits & fluids derived from hydrocarbon reservoirs
  34. 34. Sandstone Uranium Deposits & Hydrocarbon ReservoirsSouth Texas Costal plains (Adams and Smith, 1981)Ordos, Song-Liao and Tarim basins (China) Hydrocarbons are reductants in organic-poor sandstonehosted U depositsIn Kazakhstan a spatial association between  HC-bearing reservoirs and overlying sandstone U deposits  HCs and/or H2S from HC-reservoirs migrated alongstructures and could have represented the reductants for Udeposition Franceville Basin (Gabon)
  35. 35. Characterisationof uranium sources in sandstones (magmatic inclusions)
  36. 36. U SOURCES (i) Outcropping uranium rich granites: Typically high K-calc-alkaline, peraluminous leucogranites (ii) Alteration of interbedded volcanic ash or tuff Typically high-K calcalkaline to peralkaline magmasPeralkaline magmas typically marked by high Zr content in the U-oxides (Niger ; Muhlenbach, Germany …) Characterisation of the volcanic source by magmatic inclusion study
  37. 37. TECTONO-LITHOLOGIC (Akouta, Niger)
  38. 38. AIR MASSIF
  39. 39. Th vs. U volcanics rocksof Niger (Aïr, Zinder)and Nigeria
  40. 40. Importance of the uranium derived froma synsedimentary volcaniclastic contribution for uranium deposits hosted in sandstone
  41. 41. ANALCIME
  42. 42. Rhyolite pebble Volcanic shards Evidences of a volcanic contribution melt in sedimentsinclusion
  43. 43. meltinclusions
  44. 44. MAGMATIC INCLUSIONSOFFER THE POSSIBILITY TO QUANTIFY THE INITIAL METAL and VOLATIL CONTENT OF THE MAGMAS : In volcanics (ex. Streltsovka, Russie and others) In plutonites (more difficult, because less well preserved) In sediments havinga volcanic componant Melt inclusion
  45. 45. METHODOLOGY FOR ESTIMATION OF THE U POTENTIAL OF VOLCANIC ROCKSAnalyse of altered whole rocks : ICP-AES et MS Sélection of the inclusions and homogeneization at high temperature Analyse of the magmatic inclusions : - electronmicroprobe : major elts - ionic microprobe IMS3f : traces Massbalnce calculation between whole rocks / melt inclusions Évaluation of the quantity of mtals and et volatils loss / volume of rock
  46. 46. Melt inclusion geochemistry from sandstone quartz grains
  47. 47. Comparison melt inclusion composition from sandstone & Air rhyolites Air rhyolite field
  48. 48. Melt inclusion geochemistry from sandstone (Shand diagr.) Al/(Na+K+2Ca)
  49. 49. Th - U geochemistry of magmatic inclusion from sandstone 20
  50. 50. Recent eruptions at the Yellowstone caldera (64 x 40 km) The biggest occurred at 2.1 Ma  Huckleberry Ridge ash bedThe 3rd largestat Long Valleyin Californiaproduced the Bishop ash bed. Credit: USGS
  51. 51. EVOLUTION of U-GEOCHEMISTRY DURING EARTH HISTORY 4 0.45 Ga to presentMiddle Silurian  land plant apparition  reduced terrestrial clastic sediments U trapping in porous organic matter bearing continental sandstone Intraformational sandstone hosted deposits : - Tabular - roll front - tectonolithologic ... but when the reductant corresponds to migrated fluids deriving from deep seated oil reservoir trapped in permeable continetal sandstone  the deposits can be older than Silurian Ex. : - Oklo deposits - U-rich arkosic sandstone representing the source of most anatectic pegmatoids of Rössing type (metamorphosed equivalent of Oklo)
  52. 52. U DEPOSITS FROM THE FRANCEVILLE BASIN: TYPICAL EXAMPLES OFPRE-SILURIAN SANDSTONE HOSTED U-DEPOSIT RELATED TO REDUCED FLUID MIGRATION FROM AN OIL PRODUCING FORMATION
  53. 53. Franceville Basin GABON GABON Cameroun Lastourville2 Gabon Basin Guinée MASSIF DU Chaillu Og o Libreville HAUT-GABON Congo Massif ou é Mole0 Boyindzi d’Ondili Mounana Lastourville Oklo N Og oo ué OCE rz Okélobondo Franceville 10 km AN MASSIF DU Mabinga2 CHAILLU Bangombé Séries du Francevillien A Congo rz T Mikouloungou L A Formation FA > 500 m N Moanda T IQ Socle archéen U E 0 100 km Failles majeures Franceville 10 12 14 Gisements d’Uranium rz Zones de réaction Villes principales
  54. 54. FE à Stratigraphic succession FC From Weber (1968) FB2 Mn-rich layers Dolomitic layers Pelites FB1 U Mineralization Coarse grained with FA Sandstone Mnz et Zrn1000 m Basal conglomerate Archean basement
  55. 55. Oklo - Okélobondo Couche C1 Zones deW minˇralisˇe rˇaction E 15 Oklo carri¸re 1-2 3-6 7-9 Ampˇlites FB Gr¸s FB 13 10-16 OK84bis Okˇlobondo mine Socle100 m Gr¸s FA cristallin
  56. 56. Pétrographie minéralisations dans le grès Ca Qzd QzdEch. OBD.96-9c : Ech. OBD.96-23 : Okélobondo MO minéralisée U-Pb-S Okélobondo
  57. 57. M Fracture N-So FB pelites Redox fron td Fluide Hydrocarboné U mineralisatione Evaporitic layers FA carbonates F1l Fine grained non- Coarse silicified F4 Silicified FA FA sandstone Silicification - F3 Zr-P-Pb-TR-UVI F2 Diagenetic brine expulsed duringUVI erate compaction nglom sal co UVI FA Ba UVI Recharge Météorique Basement “chaude” et peu salée
  58. 58. U-enrichment in metamorphosed epicontinental platform sediments Archean: Litsk area, NE Kola Peninsula, Russia, U pegmatoids “Hudsonian” S.L. : Wollaston and Mudjatik synsedimentary U enrichment : in meta-arkoses (Duddridge Lake), calcsilicates (Burbridge Lake & Cup Lake) in pegmatoids (Charlebois alaskites). Steward Lake, Québec, Canada Northern Québec, Ungava Bay and Baffin Island, U-pegmatoids : Lake Harbour Litsk district, Kola Peninsula, Russia, U pegmatoids, Wheeler Basin, Colorado: U- pegmatoids Orrefjell, Norway: U-pegmatoids Southern Finland : Late orogenic potassic granites Crocker Well, Olary Province, Flinders Range, South Australia Six Kangaroos area of Cloncurry-Mt. Isa District, Australia Nanambu, Nimbuwah, and Rum Jungle complexes, Katherine-Darwin area, Australia “Grenvillian” S.L. Occurrences : 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” Occurrences : Rössing, SH, Rössing South, Valencia , Ida, Goanikontes,
  59. 59. LOOKING FORWARDMajor avenues for research & exploration for sandstone U deposits (1) : Sandstone related deposits represent more than 1/3rd of world U deposits andconsiderable resources are still wating to be discovered in many parts of the world In the new UDEPO data base new types of sandstone related U deposits havebeen introduced to account to their diversity Transitions exists between some synsedimentary uranium deposits, tabularsandstone type models, unconformity related model and some metamorphicuranium deposits (Katanga).The role of oil reservoir fluids (brines and associated marine hydrocarbons)migrated through faults into sandstone reservoirs as a major reductant forsandstone hosted U deposits:  change the exploration strategy:  looking for oil traps at the scale of the sedimentary basins  change in the distribution of oxidized vs reduced zones for roll fronts  open permeable pre-Silurian siliclastic formations for exploration
  60. 60. LOOKING FORWARDMajor avenues for research & exploration for sandstone U deposits (2) : Looking more systematically for volcanic U contribution in continentalsandstones by magmatic inclusion studies  improve the quality of the U sourceAustralia is the first U province of the world but presents a huge deficit ofsandstone related U deposits:  large potential for further discoveriesVitim-type paleovalleys largely underexplored worldwide (except Russia, Mongolia) Sustainable development of sandstone U deposits by the recovery of associatedrare elements (rhenium, REE, … )

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