Airborne and ground geophysical evaluation of potential mineralized zone in parts of Ilesha schist belt, southwestern Nigeria

Abstract

Integrated airborne and ground geophysical studies were conducted in parts of Ilesha schist belt, southwestern Nigeria. The goal was to provide a useful guide for mineral prospecting, with the hope of considerably narrowing down the future search for mineral deposits within the study area. Aeromagnetic and aeroradiometric data were analyzed for the reconnaissance study. In addition, the reduction-to-equator transform, analytic signal, tilt derivative, and Euler deconvolution filters were applied to the aeromagnetic data to enhance shallow and deep geologic features. The aeroradiometric data were used to determine spatial variations in the concentrations of uranium (U), thorium (Th), and potassium (K) in near-surface rocks and to map spatial lithologic changes. The 2D-magnetic sections, radiometric profiles, inverted resistivity, and induced polarization (IP) sections were generated from the integrated geophysical data. The electrical resistivity tomography (ERT) results reveal the subsurface heterogeneity (to a depth of approximately 197 m) and varied geoelectric layers (topsoil, lateritic-clay, weathered rock, and basement rock). The IP sections show varying degrees of chargeability and features that suggest the presence of disseminated mineralized bodies concealed in some areas. The overburden thickness varies between 4 and 85 m as determined from the 2D-magnetic and electric resistivity sections. Anomalous peaks on profiles of elemental ratios (eTh/K, eTh/eU, and K/eU) correlate with the results of IP and ERT. Data sets are well correlated and highlight areas with relevant structural and lithologic signatures favorable for mineral deposition. The methodology adopted in our research is well adapted, and the interpretation techniques provided insight into regional and local lithostructural settings. These anomalous areas are suggested as targets for future exploration works.