Seismic methods for the detection of kimberlite pipes

Abstract

The results of a seismic experiment conducted in Northern Territory over known kimberlite pipes are shown. A very low reflectivity sedimentary sequence and unfavourable near surface conditions resulted in a poor quality surface seismic data. The delineation of the external kimberlite pipe shape at depth, based on the principle of using the P-wave reflections that terminate against the pipe flanks, is not simple. However, by a combined analysis of P and S-reflected waves the pipe shape and its structure may be recoverable from seismic data. In this experiment, most of the seismic energy produced by an explosive charge at a shallow depth generated shear and guided waves rather than P-waves. Totally refracted P, S and guided waves generated additional wave modes in a kimberlite pipe that are used to precisely determine pipe location and its diameter. We also show that single borehole imaging has a potential for the delineation of the external pipe form and structure. The use of such unconventional seismic methods may be the solution for assisting an economic assessment of individual kimberlite pipes in the Northern Territory.