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TitleFormation of the high-grade Triple R uranium deposit revealed by Fe and S isotopes in pyrite
AuthorMount, S M; Potter, E GORCID logo; Yang, Z; Fayek, M; Powell, J WORCID logo; Chi, G; Rizo, H G
SourceGeochemistry: Exploration, Environment, Analysis 22, 3, 2022 p. 1-25, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20210457
Mediapaper; on-line; digital
File formatpdf
ProvinceAlberta; Saskatchewan
NTS74E; 74F; 74G; 74H; 74I; 74J; 74K; 74L; 74M; 74N; 74O; 74P
Lat/Long WENS-112.0000 -104.0000 60.0000 57.0000
Subjectsgeochemistry; mineralogy; uranium; iron; isotopes; stable isotope studies; Athabasca Basin; Patterson Lake Formation
Illustrationslocation maps; photographs; cross-sections; images; figures; geochemical charts; tables
ProgramTargeted Geoscience Initiative (TGI-5) Uranium ore systems - fluid pathways
Released2022 06 22
AbstractThe Patterson Lake corridor (PLC), located on the southwestern margin of the Athabasca Basin, contains several basement-hosted uranium deposits that formed via protracted, structurally controlled fluid-rock interactions. Using multiple generations of pyrite grains (pre-, syn- and post-mineralization) from the Triple R deposit, in-situ iron isotopic analyses revealed large intra-sample and -grain variations (d56Fe values ranging from -2.21 to +1.67 per mil) whereas sulfur isotopes yielded minor variations (d34S values ranging from -4.44 to + 5.3 per mil) relative to natural isotopic variations for both elements. The wide range in d56Fe values supports textural and chemical evidence that fluctuating oxidation states and chemistry in the fault zone fluids caused multiple generations of pyrite oxidation and precipitation. Sulfur isotope data from shallower mineralized zones show a slight enrichment in heavier isotopes consistent with limited Rayleigh fractionation. However, when coupled with iron isotope data, the overall dataset supports a sulfur-rich, open system wherein heat from intrusions at depth and fault movements drove sulfur-rich fluids upwards, causing precipitation of pre-mineralization pyrite and graphite. During fault reactivation, fluid pressure fluctuations between hydrostatic and sub-hydrostatic regimes drew oxidizing, uranium-bearing, basinal brines down into the basement to react with sulfides in the host rocks and deeply sourced, H2S-bearing reducing fluids. These redox reactions and fluid mixing resulted in precipitation of uraninite and syn-mineralization pyrite. These results further support the importance of structural control, repeated faulting and thermal anomalies in the basement for mineralization, necessitating re-examination of the current exploration model for unconformity-related uranium deposits.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. This contribution proposes how variations in the chemistry and isotopic composition of the mineral pyrite associated with the deposits provides insights on critical components required to form the deposits. These results suggest modification of the exploration model to expand beyond traditional metapelite host rocks, focusing instead on faults in the basement associated with elevated paleothermal anomalies.

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