A Combined Ingress-Egress Model for the Kianna Unconformity-Related Uranium Deposit, Shea Creek Project, Athabasca Basin, Canada

摘要

The Kianna deposit is an unconformity-related uranium deposit in the western Athabasca Basin, hosting mineralization in three zones: (1) perched in sandstone above the unconformity, (2) unconformity and shallow basement hosted, and (3) deep basement hosted. In situ secondary ion mass spectrometry was used to obtain radiogenic and stable isotope data to update the genetic model for the Kianna deposit. Primary basement hosted ingress-style mineralization, intergrown with hematite and muscovite, has a minimum U-Pb age of similar to 1500 Ma. Recrystallization of basement uraninite occurred at similar to 1100 Ma with the precipitation of coarse grained illite. Late basement uraninite precipitated with fine-grained illite at similar to 850 Ma. A separate, deeper basement pod formed at similar to 1280 Ma. Egress-style mineralization at the unconformity and perched uraninite in the sandstone, intergrown with aluminophosphate sulfate minerals and chalcopyrite, formed at similar to 750 Ma. Later unconformity and perched uraninite precipitated with hematite, pyrite, and chalcopyrite at similar to 500 Ma. Sulfides coeval with unconformity and perched uraninite have delta S3+ values ranging from -1.9 to +8.1 parts per thousand and 15.1 to 25.4 parts per thousand, indicating two sources of sulfur: sulfides in the metamorphosed basement and aluminophosphate sulfate minerals in the sandstone. Average delta O-18 and delta D mineral values for muscovite are 0.7 +/- 4.3 parts per thousand and -33 +/- 12 parts per thousand, respectively, suggesting formation from a marine brine. Average delta O-18 and delta D mineral values for coarse-grained illite are 0.4 +/- 4.1 parts per thousand and -79 +/- 16 parts per thousand, respectively, indicating formation from hydrothermal fluids, whereas fine-grained illite delta O-18 and delta D mineral values are 6.5 +/- 1.6 parts per thousand and -144 +/- 21 parts per thousand, respectively, suggesting formation from meteoric fluids.