SEISMIC INVESTIGATION OF A FORT A LA CORNE KIMBERLITE, CENTRAL SASKATCHEWAN
Matieshin, Scott D
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The program designed to evaluate the suitability of seismic reflection investigation techniques for kimberlite exploration was embarked upon in central Saskatchewan in 1992. Field operations for this investigation yielded data of very good quality and provided an effective demonstration of the potential value of the seismic method for kimberlite exploration within sedimentary basins. Strong, continuous reflections from the top and interior of the target kimberlite facilitated an interpretation of the overall morphology and dimensions of the kimberlite that were in close agreement with, and expanded upon, previous potential field and borehole investigations. Seismic interpretation also suggests that the kimberlitic mass is comprised of several distinct kimberlite horizons,or beds, separated by thin shale layers or weathering surfaces. This apparent layering implies that the kimberlite was the product of several periods of active volcanism. Shallow marine to sub-areal eruptions followed closely by sediment deposition provides a satisfactory explanation for the excellent degree of preservation of this very rarely preserved and easily weathered rock type. The seismic investigations ere not able to resolve a source vent, diatreme, or dyke, beneath the target body. Seismic profiles did, however, recognize several ambiguous features associated with the basal contact of the kimberlite crater that may constrain the probable location of any volcanic vent too small to identify with seismic techniques. The seismic investigations identified large scale structural disturbances atypical for this region of the Western Canadian Sedimentary Basin. Fault movements along these disturbances may have utilized zones of weakness exploited previously by ascending kimberlitic magmas and therefore may provide indicators as to the orientation and location of additional kimberlitic materials at depth.