Geochemistry and Geochronology of the Kiggavik Uranium Deposit, Nunavut, Canada

The Thelon Basin, Nunavut, Canada, is similar in age, size, and geology to the U producing Athabasca Basin in Saskatchewan. The Kiggavik project area, located immediately south of the Aberdeen sub-basin of the Thelon Basin, contains U deposits and showings along a ~ 30-km-long NE–SW structural trend. The basement-hosted Kiggavik deposit, comprising three separate mineralized zones (Main, Centre, and East), is located at the northern end of this trend. Multiple styles of U mineralization and alteration were identified at the Kiggavik deposit. Disseminated euhedral uraninite (U1; 1284 ± 53 Ma) has elevated Pb contents up to ~ 14 wt% PbO and is associated with illite and hematite alteration. Vein-style uraninite (U2; 284 ± 19 Ma) forms along fractures, contains lower Pb contents (≤ 3.9 wt% PbO), and is partly altered to Ca–Si-rich (~ 4.5 wt% CaO and ~ 3.3 wt% SiO2) uraninite. Highly altered U2 is associated with galena. Late U minerals (U3) have biogenic textures and are Pb-free, indicating that they formed recently (< 1 Ma). Based on SIMS in situ U–Pb geochronology, the minimum age of uraninite at the Kiggavik deposit is 1284 ± 53 Ma; however, this is likely a reset age associated with the Mackenzie dyke event (~ 1267 Ma). Oxygen and hydrogen stable isotope compositions of illite and muscovite suggest that the Kiggavik deposit has been overprinted by high-latitude surficial fluids derived from snowmelt.