Pb and S isotopic composition of indicator minerals in glacial sediments from NW Alberta, Canada: Implications for Zn-Pb base metal exploration

摘要

Results from an indicator mineral survey conducted with till samples in NW Alberta were used to identify a glacial dispersal train of sand-sized sphalerite and minor galena. High concentrations of dark grey to black, angular, brittle grains of sphalerite were found (100 to >1000 grains) in nine of ninety 30 kg till samples. The presence of high sphalerite grain counts in nine samples situated within a geographically restricted area argues against long-distance glacial transport, comminution, and deposition of erratic material from the carbonate-hosted Pine Point Zn-Pb deposits, located 330 km to the NE. The Pb isotopic composition of the galena grains recovered from till is similar to values obtained from Mississippi Valley-type deposits in the northern Canadian Cordillera and Pine Point and indicates that the galena is derived from similar basement sources situated along the Great Slave Lake Shear Zone. Sphalerite grains from the till have a sulphur isotopic composition significantly different from Mississippi Valley-type deposits in the northern and southern Cordillera, and are significantly different than the Pine Point deposits. These results highlight the potential to discover base metal mineralization hosted within the Cretaceous shale bedrock of northern Alberta.