The geology of the McClean uranium deposits, northern Saskatchewan

Abstract The McClean uranium deposits are in northern Saskatchewan, 11 km west-northwest of the Rabbit Lake mine. Their average grade is 1.8% U3O8 and they contain 6,350 tonnes of uranium oxide in seven pods of variable grade and mineral assemblage. They are hosted by both basal Athabasca Group and the regolith developed on the underlying crystalline basement. The major mineral fades are: sulphide, arsenide, 'bleached', and hematite, with the important uranium minerals being coffinite, uraninite and pitchblende.
Abundances of carbon and sulphur isotopes are consistent with their derivation from pyritic graphite in basement gneisses. Isotopes of oxygen and hydrogen suggest mineralizing fluids were aqueous and at temperatures of about 200 oC. Ar39/Ar40 laser age determination ofillite indicates mineralization began about 1300 m.y. ago and that significant hydro-thermal alteration ceased about 1170 m.y. ago though Pb/U data suggest the deposits continued to evolve into the Mesozoic.
The deposits are interpreted as the result of oxidizing ground water stripping uranium and other metals from either the Athabasca sandstone, especially the heavy mineral layers, or from the regolith, and precipitating these when encountering a warm reduced fluid emanating from the basement.
Keywords: Mineral exploration, Geology, McClean deposits, Uranium, Saskatchewan, Athabasca Group, Mineralization
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Summary: On February 15, 1984 Finance Minister Lalonde presented to Parliament a budget heavily flavoured with the current consultative mood of the Government. Notably absent from the budget was the typically long list of tax changes of immediate effect. Instead, the bulk of the budget papers consisted of a wide variety of white papers on significant topics that would have afar reaching impact on the future of all Canadians.This month, Tax Notes examines the highlights of Mr. Latonde's budget.
Publication: CIM Bulletin
Author(s): ROBERT B. PARSONS
Issue: 864
Volume: 77
Year: 1984
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Summary: In order to establish some links between the 22 specimens found on the site of Les Forges du St. Maurice, their slag inclusions have been analyzed by electron microprobe. Comparison between their contents of various specific oxides allowed us to segregate them into two major groups and even to isolate two sub-groups possibly characterized by some equilibrium between their oxides and/or the type of ores used.
In all probability, limestone coupled systematically with a soil rich in hydrated...
Publication: CIM Bulletin
Author(s): M. FISET, T. VO VAN, A. GALIBOIS
Keywords: Slags, Wrought iron, Bloomery process, Pig iron, Charcoal finery
Issue: 864
Volume: 77
Year: 1984
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Summary: Besshi-type Cu-Zn (-Ag-Au±Co) deposits are tabular, stratiform volcanogenic sulphide bodies which are usually associated with mafic volcanic rocks of oceanic or intra-plate geochemistry, but which can also be found locally with ultra-mafic volcanics or subvo/canic mafic intrusions. A thick sequence of continental/y-derived clastic sediment usually encloses both the mafic volcanics and the ore. Besshi-type deposits form subaqueously, in epicratonic rifting environments, more-or-less...
Publication: CIM Bulletin
Author(s): U.S. FOX
Keywords: Mineral exploration, Besshi-type deposits, Massive sulphides, Sanbagawa belt, Blue Ridge belt, Trondheim region, Outokumpu region, Mafic volcanics, Continentally-derived sediment, Lead isotopes, Epicratonic rift environment, Guaymas basin
Issue: 864
Volume: 77
Year: 1984
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Summary: Most of the Paleozoic section of the Williston Basin is a thick accumulation of numerous carbonate to evaporite, shallowing-upward, cyclic sequences. These sediments were deposited in broad epeiric seas, and the deposition of the evaporite fades marked the final stage of each cycle. Many of the sequences display a pervasive replacement dolomite in the uppermost portion of the carbonate units. This secondary dolomitization is, at least in part, an early diagenetic event, synchronous with...
Publication: CIM Bulletin
Author(s): ALF HARTLING
Keywords: Mineral exploration, Williston Basin, Hydrocarbon reservoirs, Dolomitization, Sedimentation, Oungre Zone, Red River 'C' Zone.
Issue: 864
Volume: 77
Year: 1984
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Summary: The segregation of magmatic sulphides from mafic and ultramafic silicate magmas, in many circumstances, leaves the magma with a lower-than-normal Ni/MgO ratio, which is characteristic of both lavas erupted from the magma chamber and olivine crystallizing within it. Two end members of the segregation process are discussed; i) batch segregation and ii) fractional segregation.
In the former, the critical factor is the magma/sulphide ratio. Computer modelling suggests that where this ratio has...
Publication: CIM Bulletin
Author(s): A.J. NALDRETT, J.M. DUKE, P.C. LIGHTFOOT, J.F.H. THOMPSON
Keywords: Mineral exploration, Quantitative modelling, Magmatic sulphides, Chalcophile elements, Batch equilibration, Fractional segregation
Issue: 864
Volume: 77
Year: 1984
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