3-DIMENSIONAL (3D) ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT)

GEOPHYSICAL INVESTIGATION OF MINERAL OCCURRENCES IN USEN, SOUTHERN

NIGERIA

Enoma N., 2Ogah V. A. and 1Wilkie S.O.

Mineral Resources Engineering Department, Edo State Polytechnic Usen, Edo State.

Soma Engineering Limited, Benin City, Edo State.

Abstract

Electrical Resistivity Tomography (ERT) investigation was carried out at two (2)

locations at Usen Ovia south west area of Edo State, Southern Nigeria. This was done

with a view to target deposited minerals in the survey locations. The survey was done at

two different locations

Elawure Grammar School field environment and Old Quarry environment, located

within longitudes East and latitude North. A series of 2D

apparent resistivity data were acquired in parallel and perpendicular directions using

Dipole-dipole electrode configuration with resistivity meter SAS 1000 using electrode

separations 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 separately using RES2DINV

software producing 2D models of each line. Then the 2D data were collated into 3D

data using the inversion code RES3DINV. The images were presented as 3D slices and

block models. The total depth attained for the two locations were 15.7m (51.81ft). The

material and aggregate that fall within the resistivity range (17.8 Ωm to 46938 Ωm)

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. This research has

acknowledged the fact that the minerals that can be found in Usen are clay, sand,

laterite, sand clay, sandstone, and dolomite.

Keywords: Tomography, resistvity, aggregate, minerals, configuration.