Heat flow analyses over Bornu Basin and its environs, Northeast Nigeria, using airborne magnetic and radiometric data: implication for geothermal energy prospecting

The study presents the results of the analyses of heat flow for geothermal energy exploration on a reconnaissance basis within the Bornu Basin and its environs using an airborne magnetic and radiometric data set. The study area is bounded with latitude 11.00–13.00°N and longitude 11.00–14.00°E with an estimated total area of 72,600 km 2 . The residual of the total magnetic field of the study area was subdivided into seventy-one (71) overlapping spectral blocks of 55 × 55 and 110 × 110 km 2 windows. Spectral analysis by fast Fourier transform was performed on each overlapping block, and centroid depth and depth to the top of the magnetic source were obtained from the plots of the log of energy against wave number. The results showed that the centroid depth for the two windows ranges from 6.28 to 17.70 km and 7.83 km to 23.50 km, respectively. Similarly, the depth to the top of the magnetic source for the two windows also ranges from 1.66 to 6.12 km and 2.27 km to 6.37 km. The Curie point depth obtained for the two windows ranges from 8.78 to 32.69 km and 10 km to 42 km, respectively. The heat flow obtained using an average thermal conductivity of 2.54 Wm −1 °C −1 ranges from 55.36 to 161.18 mWm −2 and 34.30 to 126 mWm −2 for the two windows, respectively. The maximum heat flow of 80 to 100 mWm −2 indicates that a geothermal potential source was found at the southeastern part of the study area corresponding to Gwoza and Galdekore. The results of radiogenic heat flow (RHP) range from 0.80 to 2.47 μWm −3 . The maximum RHP of 2.2 to approximately 2.5 μWm −3 is considered as radiometric signatures signifying probable geothermal potential sources, which could be found at the southeastern part of the study area corresponding to Gwoza and Galdekore. The agreement between the two heat flows obtained from the analysis of airborne magnetic and radiometric data sets is an indicator that the southeastern part of the study area is a viable source for potential geothermal energy exploration.