The geology and geochemistry of the Millennium uranium deposit, Athabasca basin, Saskatchewan, Canada
Beshears, Charles J.
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The Millennium uranium deposit is located 35 km north of the Key Lake mine, Saskatchewan. Uranium mineralization occurs in a variety of styles including (1) massive replacement, (2) fracture filling veins, (3) fine-grain aggregates associated with “mini” roll fronts, and (4) disseminated grains. The chemical Pb and isotopic 207Pb/206Pb ages of the massive (style 1), vein-type (style 2), and fine-aggregate (style 3) uraninite cluster at 1400-1200 and 1100-900 Ma. The ~1400 Ma ages coincide with the primary mineralization event for many of the uranium deposits (1550-1400 Ma) within the Athabasca Basin. Unlike other uranium deposits from the Athabasca basin, disseminated uraninite (style 4) have 207Pb/206Pb ages from 1770-1650 Ma. These ages are older than the depositional age for the Athabasca sediments (~1710 Ma) and are similar to the ages from the Beaverlodge vein-type uranium deposits.