Geophysical Investigation of the Subsurface Fractures Zones Using Vertical Electrical Sounding in Kassa Volcanic Field (KVF) on the Jos Plateau, North central, Nigeria

Abstract

A geophysical investigation using geo-electrical resistivity method was carried out in the Kassa Volcanic Field (KVF) on the Jos Plateau to reveal the subsurface structural lineaments as indicated in the satellite images covering the area. The electrical resistivity method utilized the Schlumberger technique along 3 profiles. A total of 36 Vertical Electrical Soundings (VES) stations with AB/2 (current electrode spacing) from 1.5 to 215m with intervals of 50m and depth penetration capability of 70m was carried out. The results obtained revealed 3-5 lithologies sequence with thicknesses ranges between 0.1 and 70m and resistivity values of between 34 ?m and 2222 ?m.   Nineteen major fractures at various depths were intercepted at various VES stations and these are probably the zones through which the basaltic lava out poured apart from the central volcanic vent.  The VES results revealed heterogeneous nature of the subsurface geological sequence. The geologic sequence beneath the study area is composed of hard pan top soil (clayey and laterite), weathered basaltic rock layers, partly weathered or fractured and fresh basement rocks.

Keywords: Geo-electric section, Subsurface, Vertical Electrical Sounding, Kassa Volcanic Field, Schlumberger Array, Jos Plateau