ASSESSING THE MINERAL AND GEOTHERMAL POTENTIALS OF PART OF KOGI STATE, NIGERIA

Abstract

The Mineral and Geothermal Potentials of part of Kogi State was investigated through the interpretation of aeromagnetic and radiometric data of the study area. Vertical and horizontal derivatives, Analytical Signal, CET, Euler deconvolution and Spectral depth analysis were used for the interpretation of the aeromagnetic data while the Concentration, Ratio and Ternary images of the three radiogenic elements were used for the interpretation of the radiometric data. The analysis of both the Vertical and Horizontal Derivatives revealed features of two major components of Nigerian geology construed in the study area based on the degree of distortion to the magnetic signatures. The NW and SW portion of the area is basement covered by short wavelength magnetic anomalous signatures that are the characteristic of outcrop and shallow intrusive magnetic bodies, while the remaining part of the study area is characterized by medium to long wavelength magnetic signatures that are attributes of sedimentary formations. 1VD map was helpful in delineating mineral potent lineaments. Result of the Analytical Signal amplitude revealed regions with shallow intrusive magnetic rocks having high amplitudes ranging from 0.174 to 0.579 nT/m, while regions with magnetic rock intruding into sedimentary formations at greater depths, have medium to low amplitudes ranging from 0.021 to 0.157 nT/m. Analyses due to Central Exploration Targeting grid revealed lineaments and structures trending NE-SW and E-W. Euler depth analysis revealed structures with greatest depth of 1252 metres and least depth of 27 metres. Radiometric signatures from the K/Th ratio map revealed portions around Latitude 8°00’ NW and 7°30’ SW having values above known threshold of 0.2 %/ppm for un-altered rocks, to be hydrothermally altered due to K enrichment. Mapping of lithology from Ternary map revealed K-Feldspar mineral bearing rocks dominated the NW and SW regions, while sandstones, ironstones, mudstones, shale, alluvium and other fluvial sedimentary lithologies dominated the sedimentary North-east and South-Eastern regions. Structures trending NE-SW and E-W mapped in the basement region of study area which also coincided with the zones of hydrothermal alterations and thus represents the zones of significant mineralisation in the study area. Result of Spectral depth analysis on the aeromagnetic data showed that peak values of geothermal gradient and Heat flow were 66 °C/km and 166 mW/m2 respectively, and occurred at the western edge of study area with a Curie point depth of 8 Kilometres.