Spectral Gravity-Based Mapping of Geothermal Potential in South-Eastern Nigeria: A Case Study of the Potentials in Okigwe

Geothermal energy is increasingly considered a promising and sustainable supplement to conventional fossil-fuel–based power systems, but many regions, including southeastern Nigeria, remain insufficiently investigated for geothermal potential. This study applies residual Bouguer gravity data to evaluate the geothermal characteristics of the Okigwe area within the Lower Benue Trough. The work aims to estimate Curie-point depth (CPD), geothermal gradient, and heat flow using gravity-based spectral analysis, with attention to zones influenced by intrusive dykes that may indicate elevated thermal conditions. Residual Bouguer gravity data from the Nigerian Geological Survey Agency were analyzed using standard processing workflows. The study area was divided into 25 spectral windows for frequency-domain analysis. Radial power spectra derived from Fast Fourier Transform were used to estimate shallow and deep gravity source depths. CPD values were inferred indirectly from gravity-derived source depths; these were then used to estimate geothermal gradient and heat flow, recognizing the limitations of applying gravity data to a parameter traditionally derived from magnetic datasets. The results indicate relatively shallow CPD estimates (5.2–8.2 km), high geothermal gradients (>70 °C/km), and elevated heat-flow values (211–329 mW/m²). These values suggest the presence of possible geothermal anomalies, although the magnitudes are unusually high and should be interpreted with caution. Linear positive gravity anomalies and shallow source depths indicate probable intrusive dyke structures near the Ohia River, Ekwe, and Dimnaeze areas. These features may act as thermal pathways and contribute to localized geothermal anomalies. The integrated gravity-based approach identifies zones with elevated thermal signatures, particularly where intrusive structures coincide with shallow CPD and high heat-flow values; however, these indications require verification with magnetic, drilling, or temperature data before firm geothermal classifications can be established. This study provides a preliminary gravity-based thermal assessment of the Okigwe region and establishes a foundation for future investigations using complementary geophysical and geological datasets.