U-Pb isotopic ages and associated REE geochemistry from the Phoenix and Gryphon uranium deposits (Wheeler River), Athabasca Basin, Saskatchewan, Canada

The Wheeler River Project hosts the high-grade Phoenix (sandstone-hosted) and Gryphon (basement hosted) uranium deposits. The property is located within the eastern part of the prolific Athabasca Basin, overlying a crystalline basement complex of Archean/Paleoproterozoic age. The chemistry, isotopic ages, and rare earth element patterns of uranium oxides were determined for four representative samples; two from each deposit, so to establish the conditions and timing of primary and secondary mineralization events at each deposit. The oldest zones in uraninite (i.e. 1433 +/- 15 Ma, 1340 +/- 17 Ma, 1275 +/- 1517 Ma) for the three oldest samples (WR403, WR525, WR569A) are considered tentatively to be primary mineralization ages. These ages and their associated REE contents are quite different for each sample, which means that the conditions and the timing for each generation of uraninite/uranium oxides were different. This difference is visible between deposits (Gryphon vs. Phoenix), but also at the scale of one deposit (Phoenix). The similar to 1430 Ma age coincides with the primary mineralization event recorded by many of the uranium deposits (1550- 1400 Ma) within the Athabasca Basin. The similar to 1340 Ma age coincides with that from the basement-hosted Millennium uranium deposit. The similar to 1275 Ma event is identical within analytical error to the emplacement age of the Mackenzie dykes cutting the Athabasca Basin. Younger age determinations within the three oldest samples most likely reflect secondary fluid events. In summary, these new results provide good evidence for multiple primary and secondary events, both between and within deposits, on the Wheeler River property.