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Uranium Transport and Deposition and Uranium Deposits Stephen J. Piercey + Jonathan Cloutier HYDROTHERMAL SOLUBILITY OF U • Uranium occurs in crustal environments in two valence states: 1. U4+ (uranous Ion) 2. U6+ (uranyl Ion) HYDROTHERMAL SOLUBILITY OF U • In magmatic (silicate melt) environments U exists as U4+ making it a highly (melt) incompatible element, so: • U resides only in a few “accessory” minerals ⇨ e.g., zircon, monazite, apatite, titanite, allanite • U thus becomes highly concentrated in residual melts & late-crystallizing minerals such as those above From Kyser, 2014 HYDROTHERMAL SOLUBILITY OF U • In hydrothermal environments it is readily oxidized to U6+ commonly forming soluble complexes with: • • • • fluoride (pH <4) Acid chloride (T > 100 °C, low pH) Acid phosphate (5 < pH < 7.5) Near Neutral carbonate (pH > 8) Alkaline From Kyser (2014) Precipitation of Uranium • • • To form uranium minerals (e.g., uraninite - UO2) we need to cause soluble uranium to precipitate. This is generally a redox reaction where a soluble uranium form in an oxidized solution reacts with some reactant that is reducing (i.e., the fluid is reduced leading to precipitation). Reductants such as: • organic matter; • reduced sulfur (H2S or HS-); • sometimes, ferrous iron (Fe2+); • or another fluid (with lower fO2) Examples of Uranium Precipitation • At high temperatures, uranous minerals (e.g., U4+O2 uraninite) are often associated with ferric oxides or hydroxides, implying REDOX reactions such as : U6+O2(CO3)34-(aq) + 2Fe2+O (rock)+ H2O U4+O2(Uraninite) + 2Fe3+O(OH)(goethite) + 3CO2(g) + O2(g) Examples of Uranium Precipitation OR ☞ , U6+O2(CO3)34-(aq) + 2Fe2+O (rock) Hematite + H 2O U4+O2(uraninite) + Illite Fe23+O3(Hematite) + 3CO2(g) + O2(g) Millennium deposit - Athabasca Basin Unconformity-related U HYDROTHERMAL SOLUBILITY OF U • At low temperatures, the most important complexes are likely to be: • • • UO22+(aq) UO2(CO3)n2-2n(aq) Most effective precipitation mechanisms are still redox reactions, with reductants such as Fe-bearing minerals, reduced sulfur and organic carbon. ORE PRECIPITATION OF U • In these lower T environments U precipitation is often hypothesized as linked to U-bearing fluids encountering reduced S, producing redox reactions such as: 4U6+O2 (CO3)34-(aq) + HS- (aq) + 15H+ + 2Fe2+ + H2O 4U4+O2 (uraninite) + SO42-(aq) + 12CO2(g) + 8H2O + ½O2(g) ORE PRECIPITATION OF U • Many deposits formed by low T processes in sedimentary sequences show textural evidence of U minerals directly replacing organic matter • e.g., sandstone-hosted deposits in Colorado Plateau district direct replacement of coalified fossil plants (including entire tree logs) by uraninite and coffinite Uranium deposits are formed after sandstone deposition by U-bearing hydrothermal fluids that replace original plant material with U-minerals. Uraninite Petrified Wood, Coconino Cty, AZ Foos, 1999 galleries.com Uranium Deposits of the Colorado Plateau MAIN URANIUM MINERALS “UNOXIDIZED” ORES • • • • • • • • Uraninite UO2 Isometric Full solid solution with Thorianite ThO2 Isometric to hexagonal “Pitchblende”: A varietal name for poorly crystalline (often colloform) uraninite Brannerite (U,Ca,Y,Ce)(Ti,Fe2+)O6 Monoclinic Coffinite (U,Th)[(OH)4x|(SiO4)1-x] Tetragonal Uranothorite (Th,U)SiO4 Tetragonal All these minerals generally (brownish-)black – except thoriteuranothorite is brownish-yellow URANIUM MINERALS “SUPERGENE” ORES & WEATHERING PRODUCTS • • • Uranophane Ca(UO2)2[HSiO4]2•5H2O Monoclinic Autunite Ca(UO2)2(PO4)2•[10-12]H2O Tetragonal Carnotite K2(UO2)2[VO4]2•3H2O Monoclinic Carnotite ⇨ Generally bright greenish-yellow ⇨ Commonly formed by simple surface weathering of uraninite or other primary U minerals ⇨ This can produce a valuable indicator “gossan” S. Wolfsried Typical yellow gossan on pitchblende ore in granite D. Wilton Deposit types 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. (Source: Kyser and Cuney, 2008) Uranium resource By Country By deposit type (Source: Kyser, 2014) Uranium resource (Source: Wikipedia, 2014) World U3O8 Production 2004 (T) Source: Globe&Mail 11/02/06) WORLD RESOURCES OF U • • • Unconformity-Type U Deposits in Canada and Australia currently contain >33% of World Resources Olympic Dam MesoProterozoic IOCG Deposit contains >31% (but @ 0.03% U) 30,500 Younger sandstone-hosted deposits in US, Kazhakstan & Niger contain ~18% after Jefferson et al, 2007 (Source: Kyser,2014) PRODUCTION OF U (Source: Kyser, and Cuney 2008) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. * Average crust: 1.7 ppm * (Source: Kyser and Cuney, 2008) Misra, 2002 From Cuney (2010) U Deposits - AGE SIGNIFICANCE • QPC-hosted Paleoplacers formed 2.8 - 2.2 Ga • • Paleosurface-related unconformity-type deposits most abundant 2.0 - 1.5 Ga • • Base of Proterozoic sedimentary basins Uraniferous black shales peak Cambrian-Devonian • • U persistent in surface placers due to more reducing ocean and atmosphere conditions Only a potential resource (≤100 ppm U3O8) Sandstone-type (e.g., Southwest USA) are generally < 400Ma RECOMMENDED READING • • • Unconformity Associated U Deposits of the Athabasca Basin; Jefferson et al. 2007, Kyser and Cuney 2008, Kyser 2014 Suppl_QPC&U-Solubility Suppl_OlympicDam (Source: Kyser and Cuney, 2008) Conglomerate-Hosted “PaleoPlacer” Conglomerate-Hosted “PaleoPlacer” • Hosted by quartz-pebble Conglomerates (QPC) of L. Archean - E. Proterozoic ⇨ Most are > 2.2 Ga • • Up to 0.2 % U3O8 – although virtually U-free, Au-bearing examples exist (e.g., Jacobina, Brazil) Typical host-conglomerate represents fluvial braided stream deposit Conglomerate-Hosted “PaleoPlacer” • Conglomerate Matrix Mineralogy includes: • quartz • zircon, monazite, chromite, rutile, leucoxene (after primary Ti-minerals) • sericite, chlorite, chloritoid (after primary detrital minerals) Conglomerate-Hosted “PaleoPlacer” • Typical Ore Mineralogy includes: • • • • uraninite, uranothorite brannerite (Ti-association, authigenic) pyrite (up to 20% of Conglomerate Matrix) native gold (Source: Kyser and Cuney, 2008) Note Pyrite-rich interstices between pebbles. These also contain U-minerals “Paleoplacer” U in quartz pebble conglomerate. Denison Mine, Eliot Lake, ON. GSC 1995-200A Autoradiograph “Paleoplacer” U in quartz pebble conglomerate. Denison Mine, Eliot Lake, ON. GSC 1995-200A Conglomerate-Hosted “PaleoPlacer” • • • • Only substantial U production has been from Elliot Lake & Witswatersrand deposits Witswatersrand deposits produce U at 0.03 % U3O8 as a byproduct of mining 10 g/T Au Much of it from ore horizons of only 0.1m to 1m thickness Elliot Lake was a primary U producer with historical grade ~0.1% U3O8 ‘Goldfields’ are Fluvial Fan successions containing one or more ‘Reefs’ - Basal Conglomerate horizons with economic concentrations of Au Since 1886,Witswatersrand Basin has produced 48,000 Tonnes of Au – ~ 35% of all Au ever produced by Mankind Major Goldfields (Vertical Bar Pattern) Hosted by Witswatersrand Supergroup Misra, 2002 Conglomerate-Hosted “PaleoPlacer” • • Interesting feature at Witwatersrand is the common association of Au concentration with biogenic carbon at the bottom contact of individual ore horizons Interpreted as evidence of Au concentration by algal mats at > 2.7Ga “Carbon Leader Gold Ore” from Blyvooruitzicht Gold Mine, Carletonville Goldfield, West Witwatersrand , South Africa. The Carbon Leader (aka Carbon Leader Reef or Carbon Leader Seam), is a carbonaceous (kerogen + bitumen) interval (interpreted by some workers as stromatolitic) containing both native gold and uraninite. [Long dimension of photo is 2.1 cm] photo: James St. John OSU-Newark In addition to Au -Blyvooruitzicht Mine also contains estimated reserves of 251.2 Mt grading 0.025% U. ("Uranium in South Africa“, wise-uranium.org. 2012) Au and U Paleoplacers READ Suppl-QPC&U-Solubility: 3.9.3 QPC-hosted Au Deposits (p 195-197) • • This is essentially a short summary by Robb (2005) of why some workers believe that later hydrothermal processes (similar to those for GQC Deposits) led to further Auenrichment at Witswatersrand Bear in mind, however, that the initial enrichment in both Au (Witwatersrand) and/or U (e.g., Eliot Lake) was almost certainly due to a paleoplacer process Edward Burtynsky, Uranium Tailings, No.12, Elliot Lake 1995 UNCONFORMITY-RELATED U DEPOSITS Spatially associated with Unconformities between: 1. Proterozoic Siliciclastic Basins • • Relatively flat-lying, un-metamorphosed, and undeformed, Late PaleoProterozoic to Mesoproterozoic, fluvial strata Clastic sediments uncomformably deposited over highly weathered Basement, in large Intracratonic Basins 2. Metamorphic Basement • Tectonically interleaved Paleoproterozoic metasedimentary & Archean-Proterozoic granitoid rocks after Jefferson et al, 2007 DEFINITIVE CHARACTERISTICS • • U mineralization commonly associated with intersections between unconformity & faults, shear zones and fracture zones Mineralization accompanied by alteration ⇨ Illite, Kaolinite/Dickite, Chlorite and Dravite (Na-Mg-rich tourmaline) after Ruzicka, 1996 MINERALIZATION • • Massive pods, veins & disseminations of uraninite 2 subtypes: • Complex type (A.K.A. Sandstone-hosted, Monometallic, Claybounded, and Egress-type) • • Simple type (A.K.A. Basement-hosted, Polymetallic, Fracturecontrolled, and Ingress-type) • • Principally uraninite Include Ni-Co-As minerals (+ trace Au, Pt, Cu) & base metal sulphides, in addition to uraninite Complex and simple refer mostly to the source of the fluids and metal assemblages. Host rocks can be different. This is the main designator of the complexity or simplicity of the deposits. Summary of Key Features of U Deposits – Eastern Athabasca Basin Jefferson et al, 2007 Unconformity-related districts in Canada Jefferson et al, 2007 ATHABASCA BASIN DEPOSITS • • Great majority of mines & prospects located where Athabasca Group sediments unconformably overly basement Western Wollaston & Wollaston-Mudjatik Transition Domains (Eastern Margin) Significant mined deposits & prospects in the Carswell Structure (Cluff Lake Camp) - and new drill intersections at Maybelle R. and Shea Ck. - demonstrate the potential for deposits in the Western Athabasca Basin after Jefferson et al, 2007 Regional Geology of the Athabasca Region Kyser, 2014 478 Ma Known Impact Structures in Saskatchewan 100 Ma 210 Ma Although the Carswell impact occurred well after primary ore formation, the post-impact rebound/uplift of the structure enhanced surface proximity of several U deposits, including the Cluff Lake District Sask. Industry & Resources Summary of some Athabasca Basin Deposits – by Depth Deposits are found at, or near, the unconformity between: Athabasca “sandstones” (<1.7 Ga) and crystalline basement (2.7 – 1.7 Ga) (Source: Areva Resources Inc) Manitou Falls Formation McArthur River, SK Basement rocks McArthur River, SK Mineralization McArthur River, SK ATHABASCA BASIN DEPOSITS • • • • Basin sediments have an extremely long history of diagenetic and hydrothermal alteration Main episodes of U mineralization occurred ca. 1.6 Ga from migration of highly saline, oxidizing basinal brines at 180 – 240 °C Several stage of U remobilization during far-field tectonic events (e.i., Grenville Orogeny at ca. 1Ga, Assembly of Rodinia at ca. 800Ma) At least one later stage of U mineralization (fracture filling) is attributed to the circulation of cool, dilute meteoric waters (<50°C) at < 400 Ma after Wasyliuk, 2006 Wasyliuk, 2006 Remobilization of U mineralization Millennium Deposit (Source: Cloutier et al., 2009) Primary deposition at 1590Ma Style 1 (+”Perched Ore” in overlying MF) Complex Type Style 2 Simple type Dielmann (Key Lake) includes both Basement-hosted and Unconformity Ore Jefferson et al, 2007 Simple type Alteration Haloes provide a valuable exploration tool for Simple Type Deposits However Complex Type shows no distinct alteration halo in overlying “Sandstone” Complex type Note inversion of alteration zoning between the two styles Simple- vs Complex Type Deposits in the Athabasca Basin Jefferson et al, 2007 Current Unconformity-Related Models Complex Type Oxidizing Basinal fluids U Complex type + As, Ag, Co, Cu, Mo, Ni, Pb, Pt, Se and Zn Reducing Basement fluids Modified after Wilson and Kyser (1987), Kotzer and Kyser (1995) and Fayek and Kyser (1997) Simple Type Oxidizing Basinal fluids Oxidizing Basinal fluids U Oxidizing Basinal fluids + Ca + Mg, Fe Modified after Alexandre et al. (2005) +U +U Modified after Hecht and Cuney (2000), Derome et al. (2005) ALTERATION MINERALOGY Clay & Alteration Minerals (Athabasca Gp) • • Illite K(Al,Mg,Fe)2(Si,Al)4O10(OH)2 Kaolin Group [ Al4Si4O10(OH)8 Polytypes ] • • Chlorite Group • • • Kaolinite, S-Kaolinite, Dickite Mg-Chlorite, Fe-Chlorite Sudoite (Mg,Fe2+ )2Al3(Si,Al)4O10(OH)8 Tourmaline Group • • Dravite NaMg3Al6B3Si6O27(OH)4 Magnesiofoitite Mg2(Al,Fe3+)Al6B3Si6O27(OH)4 ALTERATION MINERALOGY • • Portable SWIR (short-wave infrared reflectance spectroscopy) instruments are now available for fieldmapping of alteration mineralogy Capable of rapidly distinguishing the common clay minerals of the Athabasca Basin – including the polytypes of the kaolin group (dickite, kaolinite) Spectral International Inc. Jefferson et al, 2007 Earle & Sopuck, 1989 Left hand map: alteration zones in surficial material & Outcrop of the Athabasca Group Right hand map: % of samples with illite/(illite+kaolinite) > 60% from U/C+10m to top of Athabasca Group Regional illite, chlorite & dravite (B) Anomalies – SE Athabasca Basin Wasyliuk, 2006 Alteration Zones Cross-Section – Cigar Lake Wasyliuk, 2006 Alteration Zones Cross-Section – Deilmann (Key Lake) Wasyliuk, 2006 Alteration Zones Cross-Section – McArthur R. (P2 North) Generalized alteration models for subtypes of simple deposits These detailed cross sectional observations can be compiled in to two end-member alteration models for simple type deposits. 1. Quartz dissolution type model Jefferson et al, 2. Silicification type model 2007 Sandstone-Hosted U Deposits If you get involved with Sandstone-Hosted Type U Deposits it is worth reading: 3.11.2 Sandstone-Hosted Uranium Deposits (p210-214) in Suppl_QPC&U-Solubility But, for now, I am saving the details of this type, including the important class of “Roll Front” U deposits, for the 4th Year Class Wardle, 2005 LABRADOR U DEPOSITS • • • The most developed U prospects lie in the eastern part of the Central Mineral Belt (CMB), in and around the Makkovik Province terrane These include the Kitts and Michelin Deposits, discovered in 1956 and 1968, respectively. BRINEX developed these two prospects, and developed a plan in 1978-79 to mine them as a combined operation ….. then U prices collapsed. after Wardle, 2005 Figure 2. Uranium occurrences of the Central Mineral Belt and surrounding region, highlighting examples discussed in this report. Geological base map modified from Wardle et al. (1997). where they were reworked by Paleoproterozoic deformation and metamorphism. These reworked Archean rocks likely form the basement to much of the Makkovik Province and Sparks and Kerr (2009) sive suite, and older units, are in turn cut by fresh diabase dykes known as Kikkertavak dykes, which are dated precisely at ca. 2230 Ma (Cadman et al., 1993). G.W. SPARKES AND A. KERR bolites within the Makkovik Province, but locally retain their original discordance with Archean host rocks (Ryan et al., 1983). Deformed and metamorphosed supracrustal rocks, likely equivalent to the Post Hill Group also occur Group sits unconformably upon Archean basement rocks, but the more strongly deformed and metamorphosed Post Sparks and Kerr Hill group is in tectonic contact with these older rocks. The Post Hill group is strongly deformed and disrupted by shear (2009) Principal U Deposits of Labrador Central Mineral Belt Wardle, 2005 A recent exploration boom • • During mid- to late-2000s (2004-2009) there was a major staking rush and exploration boom for U. Resulted in numerous new discoveries and associated research. • • Jacques Lake, Two Time. Expansion of existing resources at Moran Lake and Michelin. Figure 2. Uranium occurrences of the Central Mineral Belt and surrounding region, highlighting examples discussed in this report. Geological base map modified from Wardle et al. (1997). where they were reworked by Paleoproterozoic deformation and metamorphism. These reworked Archean rocks likely form the basement to much of the Makkovik Province and Sparks and Kerr (2009) sive suite, and older units, are in turn cut by fresh diabase dykes known as Kikkertavak dykes, which are dated precisely at ca. 2230 Ma (Cadman et al., 1993). LABRADOR U DEPOSITS • • • Michelin (and Burnt Lake & Rainbow) are hosted by rhyolitic ash-flow tuffs of the Aillik Group At Michelin, uraninite mineralization is associated with widespread Na-metasomatism and localized hematization of these host rocks. At Jacques Lake similar mineralization style is hosted in volcanic conglomerates with andesitic compositions. Sparks and Kerr (2009) Michelin, Labrador Michelin, Labrador Jacques Lake, Labrador LABRADOR U DEPOSITS • • The Kitts-Post Hill Belt contains the rocks of the Post Hill Group Uranium mineralization is found throughout the belt adjacent to major dissecting shear zones • • Occurs as veinlets & shear-fillings in reduced units • • Kitts, Inda, Gear and Nash deposits Po-rich graphitic argillite, iron formation & mafic metavolcanics Uraninite occurs associated with pyrite, minor base metal sulphides & hematite alteration. after Wardle, 2005 Figure 2. Uranium occurrences of the Central Mineral Belt and surrounding region, highlighting examples discussed in this report. Geological base map modified from Wardle et al. (1997). where they were reworked by Paleoproterozoic deformation and metamorphism. These reworked Archean rocks likely form the basement to much of the Makkovik Province and Sparks and Kerr (2009) sive suite, and older units, are in turn cut by fresh diabase dykes known as Kikkertavak dykes, which are dated precisely at ca. 2230 Ma (Cadman et al., 1993). Sparks and Kerr (2009) Figure 5. Generalized plan view and northwest-southeast cross-sections through the Kitts deposit, illustrating the general geometry of the mineralization and presence of post-mineralization intrusive rocks; based on work in the 1970s, modified from Moran Lake • • • • • Occurs in both Bruce River and Moran Lake groups. Hosted predominantly in conglomerates parallel to Bruce River Group - Moran Lake Group unconformity. Hosted by “reduced” zones in the conglomerates. Also get uraninite-carbonate veins. Also get brecciated basaltic units with hematite alteration and uraninite (Moran Lake C Zone). Associated with V2O5. Figure 2. Uranium occurrences of the Central Mineral Belt and surrounding region, highlighting examples discussed in this report. Geological base map modified from Wardle et al. (1997). where they were reworked by Paleoproterozoic deformation and metamorphism. These reworked Archean rocks likely form the basement to much of the Makkovik Province and Sparks and Kerr (2009) sive suite, and older units, are in turn cut by fresh diabase dykes known as Kikkertavak dykes, which are dated precisely at ca. 2230 Ma (Cadman et al., 1993). Moran Lake CURRENT RESEARCH, REPORT 08-1 Figure 6. Partly schematic cross-section through the area of the Moran Lake C-Zone uranium deposits, showing thrusts inferred to repeat the basal contact of the Bruce River Group above the Moran Lake Group; modified after diagrams released on the Crosshair Exploration and Mining website. Radioactivity is reported from quartzite and conglomerate of the Seal Lake Group at the Stormy Lake showing, a Sparks and that are characterized by possible iron-rich alteration and Kerr (2009) metasomatism. The host rocks at these prospects are dis- Moran Lake G.W. SPARKES AND A. KERR Plate 6. Representative photographs of mineralization hosted by sedimentary rocks of the Bruce River Group. A) Host rocks to the Moran Lake Lower C-Zone deposit, showing oxidized (red) and reduced (grey-green) areas; uranium mineralization is associated mostly with the latter, as indicated. B) Mineralized chlorite–sericite-rich shear zone cutting the sandstone host rocks of the Moran Lake Lower C-Zone deposit, indicating local remobilization of uranium. C) Discrete zones of uranium mineralization associated with strong hematization of medium- to coarse-grained sandstone, Moran Lake B-Zone prospect. D) Strongly sheared pebble conglomerate hosting uranium mineralization associated with sericite-pyrite alteration, Moran Lake A-Zone prospect. ated within a thrust sheet that is dominated by mafic pillow lavas of the Moran Lake Group (Joe Pond Formation), with lesser amounts of argillitic sedimentary rocks (Warren Creek Formation). This contrasts with the previous interpre- Sparks and Kerr (2009) and deep-red, intensely hematized rocks that appear essentially featureless. LaCroix and Cook (2007) describe these as "jasper and chert", but their gradational boundaries with recognizable basalts are also consistent with them being the CURRENT RESEARCH, REPORT 08-1 Moran Lake Plate 7. Representative photographs of uranium mineralization and associated breccia textures at the Moran Lake Upper CZone deposit. A) Mineralized material, showing intense hematite alteration and early brecciation cut by later zones of brecciation associated with chalcopyrite. The exact location of the uranium mineralization in this sample is not presently known. B) Hematite-rich mineralized breccia cut by a later fracture that contains high-grade uranium mineralization. Note also extensive carbonate that postdates the hematite alteration. C) Spectacular breccia zone with hematite and carbonate-rich matrix surrounding strongly altered fragments of uncertain protolith. The fragments appear to have been "milled", suggesting mechanical erosion during interaction with hydrothermal fluids. D) Unbrecciated and locally mineralized host rocks from the Moran Lake Upper C-Zone deposit, which are in part of volcanic origin. Localized hematite alteration in the upper part of photo is not associated with strong radioactivity, but the intensely hematitic material in the lower part contains high-grade mineralization. mafic rocks, but the full extent of such alteration remains to Sparks and Ag over 1.0 m. Individual assays contain up to 0.63% CuKerr (2009) Two Time Zone • • • Mineralization in brecciated granites of the Archean Nain Province. Get uranium mineralization with hematite alteration. Also get chlorite and quartz alteration. Figure 2. Uranium occurrences of the Central Mineral Belt and surrounding region, highlighting examples discussed in this report. Geological base map modified from Wardle et al. (1997). where they were reworked by Paleoproterozoic deformation and metamorphism. These reworked Archean rocks likely form the basement to much of the Makkovik Province and Sparks and Kerr (2009) sive suite, and older units, are in turn cut by fresh diabase dykes known as Kikkertavak dykes, which are dated precisely at ca. 2230 Ma (Cadman et al., 1993). Two Time Zone CURRENT RESEARCH, REPORT 08-1 Plate 8. Representative photographs of uranium mineralization at the Two-Time Zone. A) Outcrop of well-developed, mineralized hydrothermal breccia, reminiscent of "tuffisite" textures developed in some high-level plutonic rocks. B) Pervasive fracturing and localized brecciation developed within granitoid rocks of the Kanairiktok intrusive suite, marginal to a mineralized zone. C) More extensive brecciation associated with higher grade mineralization, showing fragments of altered granitoid rocks in a chlorite–hematite-rich matrix. D) Contact of a post-mineralization mafic dyke (dark material); intense hematization and elevated radioactivity at the dyke contact is considered to reflect local remobilization of uranium from the surrounding mineralized granitoid rocks. This short section summarizes existing geochronologi- which these were based. The oldest near-concordant U-Pb CURRENT RESEARCH, REPORT 08-1 Sparks and Kerr Figure 3. Schematic chart showing the stratigraphic setting of uranium mineralization in the Central Mineral Belt of (2009) OLYMPIC DAM Cu-Au-U DEPOSIT “IOCG/Breccia” type Location of Olympic Dam Deposit Supergiant Cu-Au-U Deposit Middle Proterozoic Host Rocks Gawler Craton, South Australia Reynolds, 2000 Olympic Dam Deposit • Supergiant Cu-Au-U-Ag Deposit ~ 1.59 Ga based on Host Rock Age • • • Stuart Shelf Province of South Australia Hosted in large hydrothermal breccia complex wholly within Proterozoic Roxby Downs Granite (Hiltaba Suite Intrusions) Complex multi-stage hydrothermal alteration • • hematite + sericite + (chlorite + siderite + quartz) Olympic Dam Deposit • Mineralization intimately associated with hematite • • ( & with magnetite at outer margins of breccia complex) Hypogene ore zonation (laterally & vertically within breccia complex) • Cpy (on margins) ⇨ Bornite ⇨ Chalcocite ⇨ Barren Core Zone (Hematite-Qz Breccia) • • Au & Ag associated with Cu sulphides Pitchblende disseminated throughout hematitic breccia zones Ore-hosting Lithology Simplified Subsurface Geology of Olympic Dam Deposit Robb, 2005; after Haynes et al, 1995 Presence of overlying basalt and volcanic complex in this model of Hynes et al (1995) are speculative – all that remains after erosion is the breccia complex within the Roxby Downs Granite (+ minor vestiges of largely felsic volcaniclastic rocks). To date, there a number of competing models for the genesis of this rather unique deposit. Robb, 2005 McPhie et al. (2011) Olympic Dam Deposit READ SupplOlympicDam: Box 3.1 Olympic Dam • • (p157-158) - posted online. A decent short description of the deposit Bear in mind that he presents only the Haynes et al (1995) model – which is just one of many existing hypotheses for Olympic Dam Olympic Dam Deposit • • • Reserves + resources (WMC, 1999): • • • • 2,320 Mt 1.3 % Cu 0.03% U 0.5 g/T Au, 2.9 g/T Ag By any measure, a super-giant deposit “Olympic Dam-type deposit” therefore represents an extremely attractive exploration target Olympic Dam Deposit • • Olympic Dam is considered the flagship example of an IOCG deposit…………… What is an IOCG Deposit? IOCG DEPOSITS • • IOCG: Iron Oxide Copper-Gold “This class ……. does not represent a single style or a common genetic model, but rather a family of loosely related ores that share a pool of common characteristics. The principal feature they have in common is the abundance of iron oxides that accompany the ore…………..”* *T.M. Porter, 2000 in the introductory chapter to “Hydrothermal Iron-Oxide Copper-Gold and Related Ore Deposits: A Global Perspective”, Australian Mineral Foundation, Adelaide, 2000 From Williams et al. (2005) IOA Deposits • • • Cousins of IOCG but have iron oxides with apatite, with or without Cu-Au-Ag and U. Sometimes have REE. Type examples are Kiruna, Sweden and Adirondacks, USA. IOA Deposits From Jonnson et al. (2013) Olympic Dam Mine Complex Western Mining Corp