The Millennium Uranium Deposit, Athabasca Basin, Saskatchewan, Canada: An Atypical Basement-Hosted Unconformity-Related Uranium Deposit

• DOI: 10.2113/gsecongeo.104.6.815
• Publication Date: 2009-11-30T18:51:57Z
• Authors: J. Cloutier; K. Kyser; G. R. Olivo; P. Alexandre; J. Halaburda
• Keywords: Uranium ore; Basement; Uranium mine

The Millennium uranium basement-hosted unconformity-related deposit is one of the most recent discoveries deposits, and may hold as much 46.8 million pounds (18,000 metric tonnes U) at an average grade 4.53 percent U3O8. alteration zone associated with atypical, it consists predominantly muscovite rather than chlorite commonly found in other deposits Athabasca basin.

The preore stage early minor clinochlore temperatures about 275°C, interpreted to result from retrograde metamorphism basement rocks prior deposition basin. This event followed by extensive 1Mc Na-K-Fe-rich basinal brines 250°C, creating up 25 void space rocks. Subsequently, a weak chamoisite resulted Fe-Mg-Ca-rich fluids 300°C that evolved reactions between Ore uraninite has extrapolated chemical age 1590 Ma contemporaneous synore iron oxide deposited near 250°C similar δ 18O but lower D values fluids. low indicate postdepositional exchange H isotopes Cenozoic Postore dravite sudoite precipitated Mg-Ca rich fluids, same chamoisite, 185°C, filling voids created during stage. Our results pre- minerals were formed dominantly no contribution which differ some basin where basement-derived fluid influx was more significant.

Several U-Pb Ar-Ar resetting events recorded on are coincident flow induced distal orogenies, remobilizing radiogenic Pb deposit. remobilization not widespread presence restricted proximal along unconformity.