Aero-radiometric evaluation of geothermal potential in the Nupe Basin, north-central Nigeria

Abstract

This study examined the spatial distribution of potassium, uranium, thorium, and radiogenic heat production (RHP) as indicators of subsurface thermal conditions in selected parts of the Nupe Basin, North Central Nigeria, using aero-radiometric data obtained from the Nigerian Geological Survey Agency. The corrected aero-radiometric datasets, representing the measured gamma radiation of the study area, were processed using Oasis montaj software to estimate potassium (K) in %, equivalent uranium (eU) in ppm, and equivalent thorium (eTh) concentrations in ppm. The total count, ternary, and elemental ratio maps were also generated. RHP values were subsequently calculated from the radioelement concentrations using established empirical relationships. The results indicated that elevated potassium concentrations, ranging from 0.08 ± 0.02% to 2.03 ± 0.87%, are predominantly associated with crystalline basement rocks, particularly igneous and metamorphic lithologies. Thorium and uranium concentrations, with respective ranges of 14.0 ± 4.0 ppm to 21.0 ± 5.3 ppm and 3.2 ± 0.3 ppm to 5.7 ± 0.8 ppm, are more pronounced within weathered and sedimentary units. The estimated RHP across the study area yielded an average of 1.44 ± 0.08 μW/m³, suggesting relatively weak heat generation from radioactive decay processes compared to the standard threshold of 4.0 μW/m3 for geothermal lithologies. This study is limited to the radiogenic component of geothermal assessment and does not incorporate hydrogeological conditions, subsurface permeability, reservoir characteristics, or heat transport processes, which are essential for developing viable geothermal systems. Consequently, the analysed aero-radiometric data indicate a low to moderate radiogenic heat contribution.