Geophysical Investigation of the Subsurface Fractures Zones Using Vertical Electrical Sounding in Kassa Volcanic Field (KVF) on the Jos Plateau, North central, Nigeria (original) (raw)
The Vertical Electrical Survey (VES) survey of intrusive rocks in Lokpaukwu, Leru Community in Umunneochi Local Government Area of Abia State was carried out with a view to providing geology and geophysical information on the different sub-surface layers, depth, thickness, and to determine the viability of commercial mining of quarry rock materials within the study area. Eleven vertical electrical soundings were conducted using the Schlumberger array configuration covering the study area, with current electrode separation (AB/2) at 90m. The Electrical resistivity data were processed and interpreted by using IP12win software and the curve matching technique. Interpretations from the vertical electrical sounding (VES) data were used to generate Isopach and Isoresistivity contour maps in terms of thickness and resistivity of sub-surface layer using SURFER 10 software. The interpretation of the 11 VES locations suggested that only 4 of the locations could be considered to have appreciable presence of intrusive rock and the locations are VES 4, 5, 6 and 7. The overburden thickness of these VES locations is 15.8m, 10.8m, 3.42m and 15.3m respectively. From the analyses of the VES curves, it was revealed that the subsurface structure of 6 out of the 11 VES points were underlain by three layers while 4 were of five layer types and only 1 curve showed the presence of four layers in the sub-surface structure. The predominance of the three layer types as well as the low resistivity values obtained at most of the VES locations suggests the extent of fracturing in the study area. Quantitative analysis of data from the study area shows that the 'HK' type curves predominates in Lokpaukwu followed by 'A', 'H' and 'Q' type. 'A' type curves are obtained mostly in hard rock formations with conductive top soils. In this case, the resistivity of the layers will be continuously increasing (ρ1<ρ2<ρ3).