Radiometric and Geochemical Techniques for Delineating Hydrothermal Alteration Zones and Evaluating the Mineralization Potentials of the Basement Rocks in Orin-Ekiti and its Environs, Southwestern Nigeria

Abstract

The Orin-Ekiti area of southwestern Nigeria, within the Pan-African Basement Complex, exhibits marked radiometric and geochemical variations. These variations indicate complex hydrothermal and structural evolution that remains poorly understood. This knowledge gap limits the understanding of mineralization controls and the area’s resource potential. Geological mapping at a scale of 1:25,000 delineated major lithologies comprising charnockite and migmatite, with minor granite gneiss and quartz veins. Thirty-five rock samples were collected across the mapped terrain; 15 were carefully selected for detailed geochemical analysis based on spatial representation and freshness. High-resolution airborne radiometric data (K, Th, and U) from the Nigerian Geological Survey Agency (NGSA) were processed and integrated with geological and geochemical datasets to delineate alteration and mineralization zones. Data processing, performed in Oasis Montaj and ArcGIS environments, included gridding, ratio mapping, and ternary (K–Th–U) image enhancement to identify hydrothermal alteration and radiogenic enrichment patterns. Geochemical analyses involved complete digestion of samples using a four-acid and lithium metaborate/tetraborate fusion method, followed by Inductively Coupled Plasma–Mass Spectrometry (ICP–MS) at ACME Analytical Laboratories, Canada, for trace element determinations. Statistical and multivariate analyses, conducted with Microsoft Excel and SPSS, were used to evaluate compositional variations and identify geochemical associations relevant to mineralization. Factor analysis identified five significant geochemical components explaining 93.87% of the total variance. Group I (Cu–Pb–Zn–Mn–Fe) represents base-metal sulfide mineralization associated with hydrothermal alteration, while Groups II and III (Pb–As–Rb) indicate polymetallic and auriferous pathfinder associations. Strong elemental correlations such as Cu–Cr (r = 0.922) and Zn–Pb (r = 0.726) confirmed a common hydrothermal and mafic source. This study provides the first integrated radiometric, geochemical model for delineating uranium, Thorium, and Potassium base-metal potentials in southwestern Nigeria and establishes Orin-Ekiti and its environs as a promising target for future mineral exploration.