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TitleCompositional variation and timing of aluminum phosphate-sulfate minerals along the P2 fault and in association with the McArthur River Deposit, Athabasca Basin, SK, Canada
AuthorAdlakha, E E; Hattori, K
SourceAmerican Mineralogist 2015.,
Alt SeriesEarth Sciences Sector, Contribution Series 20140242
PublisherMineralogical Society of America
Mediapaper; on-line; digital
File formatpdf
ProvinceAlberta; Saskatchewan
NTS74E; 74F; 74G; 74H; 74I; 74J; 74K; 74L; 74M; 74N; 74O; 74P
AreaAthabasca basin
Lat/Long WENS-112.0000 -104.0000 60.0000 57.0000
Subjectsgeochemistry; sedimentology; uranium deposits; aluminum; metasedimentary rocks; fracture filling deposits; uranium; hydrothermal alteration; diagenesis; weathering
ProgramTargeted Geoscience Initiative (TGI-4), Uranium Ore Systems
Released2015 07 01
AbstractAluminum phosphate-sulfate (APS) minerals in the metasedimentary rocks below the Athabasca Basin record geological events including paleoweathering, alteration by diagenetic fluids of the overlying Athabasca sandstones, and uranium mineralization. Here, we present the occurrence and compositions of APS minerals in metasedimentary rocks along: i) the P2 fault (7 km of its total 13 km strike length), ii) the Bleached Zone along the unconformity between Athabasca Group sandstones and the basement (250 m outside of the P2 fault), and iii) in the Green/ Red Zone paleoweathering profile in the footwall 100 m outside the P2 fault. The APS minerals are common along the P2 fault (the main mineralization-controlling fault of the McArthur River deposit), sparse along the unconformity and rare in the basement outside of the P2 fault zone. The chemical composition of APS minerals and associated clay-sized minerals are dependent on these locations: i) APS minerals along the P2 fault occur with sudoite (± illite, magnesiofoitite) and are zoned with Sr-, Ca- and S-rich cores (solid solution between svanbergite and crandallite) and LREE- and P-rich rims (close to florencite); ii) APS minerals of the Bleached Zone are Sr- and S-rich, close to the svanbergite composition, and occur with an assemblage of dickite, kaolinite and illite; and iii) APS minerals in the Green/ Red Zone occur with sudoite and clinochlore and are zoned with Ce- and As-rich cores (close to arsenoflorencite-(Ce)) and are rimmed by crandallite and svanbergite. The occurrence of svanbergite with dickite-kaolinite-illite of the Bleached Zone suggests formation by diagenetic fluids from the overlying sandstones. Arsenoflorencite-(Ce) likely formed during paleoweathering as it is rimmed by svanbergite of diagenetic origin and found in the paleo-weathering alteration profile. Although the McArthur River deposit strikes 1.7 km, APS minerals with similar composition (close to florencite) and co-existing with alteration assemblages similar to ore zone are found along the entire 7 km of the P2 fault, including non-mineralized areas of the fault. In addition, florencite-type APS minerals are absent beyons 50 m from the centre of the fault. Florencite-type APS minerals proximal to ore also contain appreciable U (up to 16 ppm), suggesting that oxidizing uraniferous fluids travelled along the entire P2 fault and crystallized florencite. Therefore, APS minerals can be excellent vectors when exploring for fertile structures that host uranium deposits.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) 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 manuscript documents the chemistry of aluminum phosphate-sulphate minerals in relation to hydrothermal alteration along a fault hosting the McArthur River uranium deposit. The results confirm existing genetic models in which uranium-bearing fluids were focused along fault corridors, with uranium precipitation controlled by the presence of reducing media emanating from the basement rocks.