Characterization of an Uranium Deposit by 3D Borehole Seismic Techniques

The Millennium uranium deposit is located within the Athabasca Basin of Saskatchewan, Canada. The deposit, situated in metapelitic basement rocks, is controlled by multiple sub-vertical faults, and cross-faults and is overlain by ~500 m of intensely altered, porous Manitou Falls group sandstones. The rock quality directly surrounding the deposit is greatly reduced because of alteration and post Athabasca sandstone structures, which provide conduits for the migration of basin and meteoric fluids. This leads to significant risk for mine development and shaft sinking, because of the increased potential for water inflow into mine workings. To mitigate the risk involved with mining in such complex geology several projects were proposed as part of a pre-feasibility study. Of these, seismic methods were identified as the best tool to potentially identify alteration and structurally compromised zones. Subsequently, a comprehensive surface and borehole seismic program was completed in attempt to delineate these engineering hazards and to provide assurance of success of the shaft sinking and mine development. High resolution 3D, moving source profiling (MSP), vertical seismic profiling (VSP) and borehole side-scans were used at Millennium and their results were integrated, together with geological borehole logs into a comprehensive structural site model.