Jornal de Lasers, Óptica e Fotônica

Electrical Resistivity Tomography (ERT) and Very Low Frequency (VLF) Electromagnetic Methods of geophysical investigation of mineral occurrences in Usen, Southern Nigeria

Abstract

Enoma Nosakhare

Very Low Frequency (VLF) Electromagnetic (EM) and Electrical Resistivity Tomography (ERT) investigation were carried out at two (2) locations at Usen area of Southern Nigeria. This was done with a view to identify the mineral conductive areas in the survey locations. The locations were, Edo State Polytechnic field environment and Edo State Polytechnic Science Laboratory Technology environment located within longitudes   East and latitude    North. ABEM WADI (EM) instrument was used for the VLF survey. This was done so that points that indicates high conductivity for the VLF surveys were marched with those of ERT survey. The two (2) locations were found to be conductive. Then, 2D resistvity data acquisition was carried out on the two (2) locations. Data were acquired in parallel directions using wenner schlumberger electrode configurations with resistivity meter SAS 1000 using electrode separation of a = 5m and inter spacing of  L=10m making a total of 60m square grid for the lateral extent. The 2D data set were inverted using RES2DINV software producing 2D models. These models conductive points were than compared with that  of the VLF survey which indicates the presences of minerals. The minerals and aggregate that fall within the resistvity range (17.8�?�m to 46938�?�m) observed from the models are dolomite, maris, clay, alluvium, moraine, soil 40% clay, soil 20% clay, lateritic soil, sand clay/ clay sand, limonite, quartz, rock salt, lignite, syenite, basalt, schists, marble, conglomerates, and sandstone. The physical properties of lateritic soil, sand, sandstone, shale, clay and dolomite agree with some of the outcrop minerals found in the study area.