TECTONIC SETTING ANALYSIS AND GEOTHERMAL ENERGY ESTIMATION RECONNAISSANCE FOR SUSTAINABLE ENERGY DRIVE IN PARTS OF MIDDLE BENUE TROUGH USING AEROMAGNETIC DATA

Abstract

This study focused on the tectonic setting and geothermal potential for selected areas within the Middle Benue Trough, North-Central Nigeria, using aeromagnetic data. Spectral analysis was employed to estimate the geothermal gradient, heat flow, and Curie point depth (CPD). The spectral analysis was carried out by dividing the upward continuation map to 15km into 36 blocks with overlapping pixels. The depth to the centroid (Zo) and the top (Zt) were estimated from the spectrum of each block.  Geothermal gradient, depth to the bottom of the sources, Curie point depth (CPD) and heat flow were calculated using an empirical formula. Lineaments were extracted from aeromagnetic and Landsat imagery data.  Tectonically, the lineaments extracted show NE-SW, NNE-SSW, and NW-SE trends, with predominantly a few N-S trending features. From the lineament density map, it can be inferred that lineaments play significant roles in controlling geothermal potential and heat flow in the area. The lineaments identified are mostly related to structures such as joints, fault-outs, dykes, and fissures. The results of the spectral analysis revealed that the depth centroid ranges from 2.73 km to 9.09 km, the depth to the top ranges from 1.11 km to 1.89 km, the Curie point depths range from about 3.79 km to 16.38km, the geothermal gradient ranges from 35.41 to 149.89 °C/km, and heat flow ranges from 88.52 to 382.59 mW/m². The obtained values were within the established global values for geothermal provinces and sedimentary basins. The shallow depths to CPD identified are an indication of high-temperature zones, which may be due to the presence of intrusive rocks. These high heat flow values obtained from the study area are comparable to a heat flow of about 100mWm^-2 which is a good indicator for harnessing geothermal energy. Using the empirical relations of depth to CPD as a function of depth, a geothermal gradient of 3 ⁰C/100m or 30OC/Km. With an average thermal conductivity of about 105.68 to 227.63mWm-2, the area has great potential for geothermal energy, which is the most crucial and important finding of this study.