铀资源地质学：07澳大利亚铀矿实例介绍

1、Australias uranium geology, resources and potential,Ian Lambert, Aden McKay, Yanis Miezitis Uraninite Calcrete = Carnotite K(UO2)2(VO4)2.3H2O Volcanic= Uraninite; U-Mo minerals Metasomatic, magmatic = Brannerite,Australias uranium deposits3 mines and 85 deposits,Distribution of known types of uraniu

2、m deposits,No significant Quartz pebble conglomerate type U-Au deposits known,Australias Uranium resources by type of deposit,Comparison: Australia and world distribution of uranium resources by deposit types,U3O8 (t),Unconformity related uranium deposits, Northern Territory,No significant Quartz pe

3、bble conglomerate type U-Au deposits known,Unconformity related type,Unconformity-related deposit model,Mineralisation In Australia is not known above unconformity. It occurs at a favourable stratigraphic position below unconformity - in brecciated graphitic-chloritic schist immediately above dolomi

4、te unit (now largely magnesite). Faults present.,Unconformity-related uranium, Kakadu region, NT,Dean Hoatson, GA,All known uranium deposits beneath unconformity and near edges of sandstone.Localised in breccias along favourable dolomite-graphitic schist boundary,Aboriginal rock painting sites Kakad

5、u National Park,Ranger mine: Early Proterozoic unconformity U,Ranger Mill,Unconformity,Note horizontal sandstone and unconformity,Tailings disposal - Ranger No.1 open cut,Ranger No 3 open pit,Ranger No. 3 open cut,Ranger mine: Mineralised chloritic-graphitic breccia at graphitic schist/dolomite cont

6、act,Jabiluka Lease and Ranger Project Area,JABILUKA,Jabiluka 1 and 2 Orebodies,Uraninite-gold mineralisation is stratabound,Several ages of unconformity related U mineralisation in Pine Creek Inlier,1620-1740 Ma,1620 Ma,780 Ma,1620 Ma Approx U mineralisation age,Distribution of known U-rich bedrocks

7、, Pine Creek Inlier .,Uraninite present in granites with elevated uranium contents. Uranium is soluble in oxidised waters and precipitated by reduction,Some key issues,Are large unconformity U systems confined to Palaeoproterozoic-Archaean basement under largely undeformed Palaeo-Proterozoic sandsto

8、nes? Are Athabasca Basin in Canada and Pine Creek in Australia only examples?,What is the role of faulting and carbonate dissolution? Did weathering before deposition of the sandstone mobilise metals and/or provide a permeable zone for fluid migration? What is the significance of transition from gen

9、erally reduced to oxidised conditions in the Early Proterozoic?,Unconformity related U systems,Palaeoweathering zone,Uranium deposits: Hematite breccia complex type,Hematite breccia complex type,Location plan and simplified regional geology of the Gawler Craton and Stuart Shelf, South Australia (aft

10、er Reeve minor Cu),In hills to west of Beverley sandstone U deposit,Some features of hematite complex type U deposits,Hematite breccia complex uranium systems = uraniferous iron oxide copper gold deposits (IOCGs) Olympic Dam is by far largest example Criteria that distinguish uranium-rich IOCGs from

11、 (more common) uranium poor IOCGs: Explosive volcanic activity; regional faults and/or diatreme vent zones Regional Na(K)-Ca, and/or iron oxide alteration; hematite alteration overprinting magnetite alteration High palaeo-geothermal gradients (still somewhat elevated) and large volumes of U-enriched

12、 felsic intrusive and volcanic rocks(I-type, oxidised, high heat granites);,Uranium deposits: Sandstone type,Sandstone type,Sandstone uranium deposits:Lake Frome Embayment,Beverley uranium recovery plant - ion exchange technology,Beverley - commercial in situ leach wellfield,Beverley Sandstone U: Ge

13、ological section,U-rich Proterozoic granites, Frome Embayment,U-rich granites,Uranium deposits: Surficial (Calcrete) type,No significant Quartz pebble conglomerate type U-Au deposits known,Surficial type (calcrete),Yeelirrie:Calcrete type,Uranium contents of some rocks and waters,Arenites average 1.

14、5 ppm Pelites average 3.5 ppm Evaporites average 0.1 ppm Phosphorites up to 300 ppm Weathering products (laterite/bauxite, etc.) average 10 ppm Biotite and graphitic schists, average 4 ppm Gneisses 3.5 ppm Granite 5 ppm Alkaline igneous rocks 10s 100s ppm Groundwaters in igneous and metamorphic terr

15、anes average 5-10ppb Mineralised aquifer 10-400 ppb Note: Igneous rocks/gneisses with more than 10 ppm U typically contain uraninite, which is readily leached,Geological provinces and felsic igneous rocks of different ages,U-rich rocks from national geochemical database,Geoscience Australia,U minera

16、lisation and felsic igneous activity,Hot Southern Continent,High proportion of U-rich felsic igneous rocks are Proterozoic high heat flows,Power from hot granites,Uranium-rich granites 250oC at 3-5 km depth. Good potential for geothermal power generation. Several pilot projects in South Australia.,P

17、roterozoic High Heat Flow Granitoids,Australian Craton was assembled by 2300 Ma. Metallogeny controlled by intracratonic basins generated by mantle underplating. Anorogenic magmatism,Regions with significant U deposits and potential,Unconformity,Calcrete,Hematite breccia, sandstone,Sandstone,Hematit

18、e breccia, sandstone, Unconformity, Intrusion related,Pine Creek, McArthur Basin,Yilgarn,Paterson,Granites-Tanami,Ngalia, Amadeus,Gawler, Curnamona cratons, overlying basins,Mt Isa Inlier, adjacent basins,Georgetown, Charters Towers,Volcanic,Carnarvon Basin,Canning Basin,Sandstone,McArthur Basin,?,I

19、ntrusion related in Arunta?,IOCG Unconformity Sandstone Calcrete Volcanic Intrusion,Some research observations:Mineral deposits through time,Oxidised atmosphere Fractionated crust,Prog. oxidn ocean,Research observations:Archaean-earliest Proterozoic: uranium in quartz pebble conglomerate,Uranium ins

20、oluble in reduced waters -detrital uraninite (+pyrite + gold): South Africa,Canada Metamorphic overprints,Prevalent distribution of major types of U deposits through geological time,From F Dahlkamp (1993),Global uranium supply and demand forecasts,Even the most conservative of international scenario

21、s imply that nuclear power will be sustained at least at current levels This requires progressive increases in mine production of uranium, as secondary supplies are depleted Increasing nuclear power generation appears likely, as various countries implement strategies to decrease greenhouse emissions

22、 This will proportionally increase the demand for uranium Upper scenario of World Nuclear Association has uranium demand doubling by 2025,Global uranium supply and demand forecasts,Significantly increased production has been foreshadowed from: Canada (opening of the major Cigar Lake mine) Kazakhstan

23、 (developing several new sandstone type deposits) Australia (developing a large open pit at Olympic Dam to increase production up to fourfold) If realised, the planned increases should go a long way towards meeting the demand as secondary supplies decrease There is a need for further exploration to sustain uranium resource base Particu