Geophysical investigations for kimberlite pipes in the greenstone belt of western Kenya

Abstract

Some of the EM conductors, delineated in the greenstone belt of western Kenya during an airborne Barringer INPUT survey in 1977 and believed to be kimberlite pipe targets, have been geophysically investigated on the ground. Four of those initially investigated are reported in this paper. The results show that three of these are elliptically shaped and oriented in the general strike direction of the local geology. They are associated with a distinct magnetic signature. The magnetic source in each case seems to be deeply seated. The fourth conductor has a more or less circular surface outline. It is associated with a ground vertical magnetic pattern that appears to be of surficial origin and aligned in a north-south direction across the middle of the conductor. No geological outcrops occur on the conductors, except a few at their edges. Diamond drilling was carried out on the four conductors. Although not fully confirmed, drill core results from three of them show what appears to be vaguely defined kimberlitic material.