Le gisement d'uranium de Cigar Lake: decouverte et caracteristiques générales

Abstract The Cigar Lake uranium deposit, in the Athabasca area of North Saskatachewan, was discovered in May 1981 by Cogema Canada Ltd., as operator of the Waterbury Lake Joint Venture.
The deposit, which is devoid of direct surface expression, is located at the unconformity between the Lower Proterozoic (Aphebian) Wollaston Group metasediments and the Middle Proterozoic (Helikian) Athabasca sandstone, at a depth of 410 m to 450 m below surface.
At the end of 1984, the deposit had been defined by 105 mineralized holes over a length of 1800 m and a width of between 25 m and 105 m. It has the shape of a flat-lying lens 5 m to 30 m thick and shows a remarkable longitudinal and lateral continuity from the information obtained to date. A well defined bulge of the unconformity underlies the mineralized zone over its entire length.
The deposit appears to be controlled by an east-west-trending structure within which a particular rock fades ("augen gneiss") has developed in the graphitic metapelites of the Wollaston Group. It is surrounded by a strong alteration halo affecting both sandstone and basement, characterized by extensive development of Mg-Al rich clay minerals (illite-chlorite).
The mineralization is hosted principally by the Athabasca sandstone, and consists mainly of uraninite and sulfo-arsenides of nickel and cobalt.
Numerous geochemical and geophysical surveys have been carried out in the Cigar Lake area, and no specific geochemical or geophysical anomaly can be directly associated with the mineralized body, although there may be locally a good coincidence. However, a combination of several methods proved extremely useful in interpreting the regional geology and defining the drilling targets within the favourable areas.
Although the Cigar Lake deposit shows many similarities with several classical deposits of the Athabasca region, it is characterized by the intensity of its alteration processes and the presence of massive, extremely high-grade mineralization.
At the end of 1984, the global geological reserves estimated by geostatistics on the main mineralized "pod" of the deposit amounted to 110 000 metric tonnes of uranium at an average grade of 12.2% U, with a precision of 25% at the 95% confidence level.
Keywords: Mineral exploration, Uranium deposils, Unconformity-lype deposils, Geophysics, Saskatchewan
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Publication: CIM Bulletin
Author(s): A. SUTHERLAND BROWN
Keywords: Mineral exploration, Mineral deposits, Discovery, Prospecting, Geosciences studies, Surveys, Geological Branch studies, British Columbia
Issue: 886
Volume: 79
Year: 1986
Text
Summary: This paper covers the development of the property to its present production level of 20,000 tonnes per day from the Valley Mine. It will also review the analysis of various case studies for the expansion of the project to its full potential, and discuss the impact of the recent structural change in the copper market on the development of a large low-grade deposit such as Valley.
Publication: CIM Bulletin
Author(s): P.P. TAYLOR
Keywords: Exploration, Copper deposit, Valley copper project, Project development, Production, Capital cost, Equipment, Concentrator, Markets.
Issue: 886
Volume: 79
Year: 1986
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Summary: Geophysical test surveys were conducted with various methods (EM, IP, gravity and magnetic) over the McClean uranium deposits of the CanadianOxy-Inco Joint Venture. The results were assessed to judge the contribution each method might make toward further discoveries of graphite-associated uranium occurrences.
The best drill targets have proven to be discontinuities in graphitic conductors and locations where the latter are intersected by fracture zones in the Athabasca. The tests demonstrated...
Publication: CIM Bulletin
Author(s): F.L JAGODITS, J.E. BETZ, , N. SARACOGLU, R.H. WALLIS
Keywords: Mineral exploration, Drilling, Geophysical surveys, McClean deposits, Uranium, Athabasca Group, Electromagnetic surveys, Gravity surveys, Economic geology
Issue: 886
Volume: 79
Year: 1986
Text
Summary: The Lang Bay germanium property is a carbonaceous sandstone deposit outcropping near the Pacific coast, 100 km north of Vancouver. The germanium-bearing seams are up to 5 m thick. Where one such seam outcrops, it averages 50 to 60 g Ge/tonne. Drill core analyses have shown considerably greater concentrations of germanium at depth. Additional drilling to establish continuity and grade of the germanium-bearing strata is scheduled for 1986. The germanium occurs in association with lignite, which...
Publication: CIM Bulletin
Author(s): P.B. QUENEAU, PETER V. AVOTINS
Keywords: Rare metals, Recovery, Exploration, Geology, Mineralogy, Extractive metallurgy, Hydrometallurgy, Germanium, Gallium, Coal, Oil agglomeration, Flotation, Lang Bay
Issue: 886
Volume: 79
Year: 1986
Text
Summary: Reconnaissance geochemical mapping, based on the chemical analysis of waters, stream, and/or lake sediments had its origin in geochemical prospecting surveys carried out in New Brunswick during the 1950s. More recently, reconnaissance geochemical surveys carried out by government agencies for mineral resource appraisal purposes have been seen as a special case of regional geochemical mapping which is carried out with the aim of describing geochemical patterns for elements which may be...
Publication: CIM Bulletin
Author(s): J.A.C. FORTESCUE
Keywords: Mineral exploration, Geochemistry, Geochemical mapping, Geochemical surveys, Geoscience, Prospecting, Micromodules, Mineral resource appraisal, Lake sediments
Issue: 886
Volume: 79
Year: 1986
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