SEISMIC IMAGING OF MASSIVE SULFIDE DEPOSITS .3. BOREHOLE SEISMIC IMAGING OF NEAR-VERTICAL STRUCTURES

Surface seismic profiling is well suited for geologic provinces charac terized by low to moderate dip, but it is less effective where dips ex ceed 65 degrees due to inherent limitations of the recording geometry and processing algorithms. Vertical seismic profiling (VSP), a method used mainly for hydrocarbon exploration in sedimentary basins, overcom es this limitation by utilizing deep boreholes as an alternative acqui sition datum. Here, we evaluate the effectiveness of this method for i maging massive sulfide deposits associated with folded and steeply dip ping volcanic units near the Kidd Creek orebody in Ontario, Canada. Sm all (150-225 g) explosive charges placed in a water-filled pit provide d a consistent energy source, with sufficient band width and signal pe netration to image the target zone to a depth of at least 1.0 km. Afte r preliminary processing, the vertical seismic profile record sections were mapped into cross sectional format using a transformation based on ray tracing. This transformation facilitates the extrapolation of s ubsurface contacts updip from borehole intersections, and the resultin g images delineate several stratigraphic contacts in addition to a pro minent seismic reflection from a massive sulfide body.