APPLICATION OF GEOPHYSICAL AND REMOTE SENSING TECHNIQUES TO DELINEATE LATERITIC BAUXITE DEPOSIT ZONE IN ORIN-EKITI, NIGERIA

Abstract

This research uses geophysical techniques such as Magnetic, Electrical Resistivity Imaging (ERI) and remote sensing (RMS), to image the lateritic bauxite bearing zones in Orin-Ekiti, Southwestern Nigeria. Several parameters characterizing bauxite deposits such as vegetation, slope, and topography were established using RMS. The result shows that the study area is mostly low mountain and hilly, with an elevation ranging between 534 and 644 m and slope angle extending from 0-200. Normalized Difference Vegetation Index (NDVI) value falls under moderate vegetative cover which is one of the features indicating the manifestation of lateritic bauxite. Aeromagnetic data was utilized for generating Total Magnetic Intensity (TMI), Euler Deconvolution (EUD) and Total Horizontal Derivative (THDR) maps to enhance better understanding of bauxite deposit. Magnetic low trending NE-SW was observed in the study area. The (EUD and THDR) maps were superimposed on the geologic map to geo-reference areas that have dominant charnockite. 2-D ERI results obtained from five traverses with inter traverse separation of 45 m and traverse-length of 100 m each, established in the NW-SE direction to image the lateritic bauxite deposit based on the prospect shown from the aeromagnetic analysis. The 2-D and 3-D inversion results show bauxitic zones to be of high resistivity which ranges from 154-3814 Ohm-m, the migmatite gneiss and granitic rocks (unaltered parent rocks) are of considerably lower resistivity than the weathered charnockitic rock and by extension bauxitic zones. These different techniques used in this study have however shown that the area of interest for bauxitic deposit in Orin-Ekiti trends in the NE-SW direction with a dominant concentration in the North Eastern (NE) part. By the same token, this research has been able to substantiate the fact that bauxite deposits occur as supergene enrichment.