Gravity and Magnetic Anomaly Interpretation for Mineral Exploration in Nassarawa State

This study interprets combined gravity and magnetic anomalies to identify mineral exploration targets in Nasarawa State, North Central Nigeria. Nasarawa State has diverse solid mineral resources including bitumen, baryte, gemstones, limestone, and metallic minerals in its Precambrian basement complex. Integrated potential field interpretation can map the structural framework and lithological contrasts that control mineralisation, providing a cost-effective pre-drilling exploration tool. This study processes and interprets available aeromagnetic data from the Nigerian Geological Survey Agency for the Akwanga and Keffi map sheets, combined with a ground Bouguer gravity dataset comprising 68 stations at 1-kilometre spacing along six profiles. Aeromagnetic data are processed for RTP, THD, and analytic signal computation. Gravity data are processed to free-air and Bouguer anomaly levels with terrain correction. Regional-residual separation uses upward continuation and polynomial trending. Integrated interpretation employs Werner deconvolution for depth estimation and 2.5-dimensional forward modelling. Findings reveal strong spatial correlation between gravity and magnetic anomalies northeast of Akwanga, interpreted as mafic intrusions with potential for associated chromite or nickel sulphide mineralisation. Linear magnetic features trending east-southeast correspond to mylonite zones that host baryte veins documented in NGSA mapping reports. Five target areas combining structural complexity with anomaly amplitudes warranting follow-up are delineated. The study demonstrates the synergy of combined gravity and magnetic methods for mineral prospectivity assessment in Nigeria's basement complex terrains.

Keywords: gravity, magnetic anomalies, mineral exploration, Nasarawa State, potential field interpretation.