oa Application of Seismic Interferometry in Crystalline Rocks - A Case Study From the Lalor Mining Area, Canada

Approximately 300 hours of ambient noise data covering an area of 4 km² were acquired over the Lalor mining area, Canada, to test the capability of seismic interferometry to image ore deposits in the crystalline rock environment. The interferometry survey consists of 336 receivers located along 9 parallel lines oriented southwest-to northeast and 7 southeast-to-northwest lines. Alongside the ambient noise survey, a larger 3D active source seismic survey was also acquired in the area and used to evaluate the interferometry results. The seismic wave field is retrieved by crosscorrelating the noise between all receiver locations in each hourly segment of passive seismic data. The crosscorrelated results of all segments are spatially summed to generate virtual shot gathers. The virtual data is processed along all 2D lines with conventional methods similar to those applied to active 3D data. The DMO-stacked section obtained reveals a number of events, some more coherent than observed on the similarly processed active seismic section. Of particular interest is an event possibly associated with the massive sulphides. A comparable event is also observed on the active seismic data. These results demonstrate the benefits of ambient noise measurements in crystalline rock environment for mineral exploration purposes.