The Application of Seismic Techniques in the Development of the Millennium Uranium Deposit, Northern Saskatchewan, Canada

Abstract

The Millennium uranium deposit is located within the Athabasca Basin of northern Saskatchewan, Canada. The deposit is situated within moderately dipping Paleoproterozoic supracrustal rocks unconformably overlain by greater than 500 m of porous Mesoproterozoic to Paleoproterozoic Athabasca Group sandstones. An unconformity, which is also a major fluid conduit, separates the basement lithologies from the overlying sandstone. Rock quality surrounding the deposit is compromised because of the effects of the significant hydrothermal alteration that has occurred syn- and postmineralization. Post-Athabasca structures, together with the unconformity, provide direct conduits for the migration of large amounts of basinal fluids to the general deposit area. To mitigate the risk involved with mining in such a complex hydrogeological environment several geotechnical surveys were proposed as part of a pre-feasibility study for potential mine development. Of these, seismic methods were identified as the best tool to potentially map the location of the unconformity, identify structurally complex zones and alteration at both the mine and property scales. Subsequently, comprehensive surface and borehole seismic programs were completed in an attempt to increase confidence in shaft sinking, delineate engineering hazards related to mine development, and provide information on the structural setting of the geology hosting the deposit. The program consisted of a surface 3D survey and multiple borehole seismic surveys. This was the first time a seismic program of this scale was undertaken for geotechnical studies prior to mine development in the Athabasca Basin. All surveys successfully mapped the unconformity and post-Athabasca structures at various scales.