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TitleGeochemical alteration and structural interpretation as an exploration vector at the Lac Cinquante Uranium Deposit, Nunavut, Canada
AuthorPilles, E; Bridge, N J; Ward, J; Berry, A; Jiang, DORCID logo; Potter, EORCID logo; Pehrsson, S; Banerjee, N R
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 35, 2012 p. 108-109
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20120203
MeetingGeological Association of Canada - Mineralogical Association of Canada annual meeting; St. John's, NS; CA; May 27-29, 2012
AreaLac Cinquante
Subjectseconomic geology; geochemistry; structural geology; alteration; alteration products; mineral occurrences; mineral deposits; uranium; mineralization; geochemical analyses; greenstone belts; Archean; structural analyses; structural controls; Lac Cinquante Uranium Deposit
ProgramGEM: Geo-mapping for Energy and Minerals Uranium
AbstractThe Lac Cinquante uranium deposit is located in the Hearne Subprovince of the Western Churchill Province. The deposit is hosted within an Archean greenstone belt that is unconformably overlain by the northeast trending Angikuni sub-basin of the Paleoproterozoic Baker Lake basin in the western Churchill Province. Uranium mineralization at Lac Cinquante consists of a 43-101 compliant inferred mineral resource estimate of 1,779,000 tonnes grading 0.69% U3O8, making Lac Cinquante Canada's highest grade uranium deposit outside the Athabasca Basin. Mineralization is hosted within a zone of strong tectonic transposition. Specifically it occurs as pitchblende in discrete veins along or at small angles with the transposition foliation and in tensional gash veins cutting the transposition at high angles. Mineralization also occurs weakly in Paleoproterozoic basal conglomerates. In this study we present results for oxygen stable isotope analyses of silicate whole-rock samples, and examine surface and sub-surface features to determine the structural controls on the deposit. Through integration of these techniques we investigate the implications for fluid flow, alteration, and mineralization of the main ore zone at Lac Cinquante.
Oxygen stable isotope analyses are effective in documenting zones of increased low-temperature fluid flow which resulted in hydrothermal alteration associated with the main zone of mineralization.
Oxygen stable sotope analyses of silicate whole rock samples have identified 20 - 50 meter wide alteration envelopes where values are elevated by almost 2 permil within, and surrounding, the main zone. Several tuffaceous units not associated with the current main zone also show anomalous enrichments up to 2.5 permil. Additionally, 1 permil enrichment halos can be traced around structural zones in the basaltic basement rocks.
Mineralization forms linear, shallow west-plunging ore shoots within the Lac Cinquante and Western Extension prospects, and steeply eastplunging ore-shoots within the Eastern Extension. The orientation of these ore-shoots potentially corresponds to the intersection of hematite-stained tensile fractures trending 050° and high-strain zones trending 110°, which are proposed to reflect areas of increased fluid flow. Combined, structural interpretation and geochemical analysis can be utilized as an exploration vector to define future drill targets. This strategy can be further applied to historic drill core to identify possible near misses during past drilling as well as geophysical targets in the region not directly associated with the main zone mineralization.

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