Integration of Aeromagnetic and Radiometric Studies to Delineate Hydrothermal Alteration and Mineralized Zones in Effon-Alaaye and Its Environs, Southwestern Nigeria

Abstract

Basement terrains of southwestern Nigeria host structurally controlled hydrothermal mineralization, but delineating alteration zones and prospective targets remains challenging due to limited surface exposure and complex deformation history. This study integrates aeromagnetic and radiometric datasets to delineate hydrothermal alteration zones and assess the mineralization potentials of Effon-Alaaye and its environs within the Nigerian Basement Complex. High-resolution airborne aeromagnetic and gamma-ray spectrometric data covering the Ado-Ekiti Sheet 244 were acquired by the Nigerian Geological Survey Agency in 2006 and processed using Geosoft Oasis Montaj 8.4 (HJ). Aeromagnetic analysis included Total Magnetic Anomaly (TMA), Reduction to the Equator (RTE), First Vertical Derivative (FVD), Analytic Signal (AS), residual magnetic separation, Euler deconvolution, and lineament extraction to map subsurface structures and lithological contrasts. Radiometric processing involved potassium (K), thorium (Th), uranium (U), potassium deviation (KD), and ternary (K–Th–U) mapping to identify lithological variations and hydrothermal alteration signatures. Integrated interpretation established spatial relationships between structures, alteration zones, and mineralization. Results reveal a structurally complex basement dominated by NNE–SSW to NE–SW trends consistent with African-wide tectonics. Magnetic lineaments, low-magnetic corridors, and clustered Euler depth solutions delineate shear zones, faults, and lithological contacts that likely acted as conduits for hydrothermal fluids. Radiometric maps highlight potassic alteration zones characterized by elevated K and KD anomalies that correlate strongly with magnetic structures. Thorium data discriminate felsic intrusions from schist belt host rocks, while uranium maps delineate a uranium-enriched zone in the northeastern sector (Alawaye–Ojejelu–Itawure axis), suggesting hydrothermal uranium mineralization. Integrated results indicate that the highest mineralization potential occurs where shear zones intersect secondary structures and coincide with radiometric alteration signatures. Consequently, Iwaiji, Ipole, Agopoti, Alawaye, Ojejelu, and Itawure are identified as priority targets for orogenic gold, uranium, and associated polymetallic mineralization.