Integrated aeromagnetic and aeroradiometric data for delineating lithologies, structures, and hydrothermal alteration zones in part of southwestern Nigeria

Abstract

Locating zones of possible mineralization potentials in part of southwestern Nigeria has been performed in this work by mapping lithology, structures, and hydrothermal alteration regions from airborne magnetic and radiometric data. Some enhancement techniques such as first vertical derivative, analytic signal, power spectrum, and center for exploration targeting grid and porphyry were used for data analysis and interpretation; in addition, the potassium to equivalent thorium (K/eTh) ratio and ternary radiometric maps were revealed to support the delineation process. The results obtained showed that the area is dominated by NE–SW, NW, NE, EW, and NS structural directions, though the structures trending NE–SW were found to be the most predominant and considered to be orientations of mineral deposits in the area. Depth estimation of shallow and deep-seated magnetic sources of the reduction to the equator (RTE) aeromagnetic data calculated using the analytic signal technique ranged from 270 to 2800 m, while power spectrum gives an average value of 2960 m. In addition, aeroradiometric analysis based on the concentrations of equivalent thorium and equivalent uranium and potassium and on the radiometric ternary map revealed lithological units and hydrothermal alterations within the basement complex. From this study, volcanic intrusions, lineament structures, and hydrothermal alteration zones were delineated. These intrusions resulted from the high content of magnetic anomalies related to the mineralized potential zones in the area. The integration of both magnetic and radiometric maps has revealed an approximate understanding between radiation zones, observed fractures, and faults in the locations between the boundaries of rock types in the study area.