ABSTRACT
The 3-Dimensional Electrical Resistivity Tomography (ERT) of Mineral occurrences was carried out in three (3) different locations at Ugonoba, EdoState, Southern Nigeria. This was done with a view to targeting mineral occurrences orgeologic materials by the application of 3-Dimensional methods of Electrical Resistivity. The presence of some out crops that a resparsely distributed in study a rea during reconnaissance survey formed part of the motivation for this research.This is to identify and quantify there for more potential mineral deposits that are essential for both industry and economic growth ofthe nation, hence, the application of 3-D ERT in the study area.
Electrical Resistivity Tomography data was acquired and carried out using PASI 16GL digital resistivity meter (Terrameter) instrument so as to investigate the presence of both surface and near surface conductive minerals and materials. Series of 2-Dimensional apparent resistivity data were generated in parallel and perpendicular directions using Wenner-wenner electrode configuration with electrode separations of 10m. Three 200m-square gridlines were generated from all the 30 traverses (lines) in the three locations with ten lines per location.The maximum spread (total length) is 200m with 50m spacing between the lines for med one grid for one location.The 2-D apparent dataset acquired were invertedseparately using RES2DINV geophysical software generating 2-D model images for each traverse line. Then,the 2-D data were collated into3-D using the inversion code of RES3DINV with the smoothness constrain which automatically determines a horizontal 3D depth slice model of resistivity distribution using apparent resistivity data obtained from a 3D resistivity imaging survey. The 3D cube was processed using Voxler and Earth Imager 3D software by collating entire square set of 2D lines together to form a single 3D data set each.
The 2D images and 3D cubes, slices and block models generated from all this geophysical software were interpreted and used to ascertain the true resistivity, thickness of lithologic formation and depth extent to any buried mineral and aggregate deposited in the study area. The total depth attained for investigation in all three location was 39.6m (129.92ft). The extracted 3D models image revealed evidence of some features such as minerals and materials in the study area; however, the suspected minerals delineated from the images of 3D geo-electrical resistivity models and depth slices fall within the resistivity range of 450Ωm and 10000Ωm. From the standard resistivity table, it can be inferred that the lithology of study area is suspected to be composed of the non-metallic type of minerals resources (i.e lateritic clay soil, ferruginouss and stone, shale, alluvium, gravel, limestone.). Using volumetric analysis method, the estimated quantity of this dominant lithology in thestudy area is± 10% of 4,903,737.2 ton.
