Geochronology and Genesis of the Bong Uranium Deposit, Thelon Basin, Nunavut, Canada

The Thelon basin, Nunavut, shares many similarities with the uranium-producing Athabasca basin, Saskatchewan; however, the uranium deposits associated with the Thelon basin are still poorly understood. The Kiggavik project area (AREVA Resources Canada) is located near the northeastern terminus of the Thelon basin and comprises multiple uranium deposits hosted exclusively in basement rocks. The Bong deposit is hosted dominantly by Neoarchean metagraywacke of the Woodburn Lake group. A five-phase metallogenetic model is proposed for the Bong deposit, with three stages of uraninite identified. The premineralization phase is characterized by host-rock silicification. Mineralization is separated into three main stages. Stage 1 uraninite (U1; ca. 1500 Ma) is preserved in highly fractured and altered disseminated grains that are overgrown by later stages of uraninite. Stage 2 uraninite (U2; ca. 1100 Ma) forms veinlets parallel to D 1 foliation and coats and fills fractures in organic matter nodules and blebs. Stage 2 uraninite is associated with pervasive illite that formed from ~190°C fluids ( δ 18 O: −6.4‰, δ 2 H: −97‰), which remobilized much of Stage 1 uraninite and completely overprinted Stage 1 alteration. At ~1000 Ma an oxidizing fluid deposited uraninite along redox fronts (U3) while altering and remobilizing Stage 1 and 2 uraninite. Post-uranium-oxide minerals include drusy quartz, calcite, and illite accompanied by uranyl phases (e.g., uranophane, Ca-U).