Estimation of Curie-point depth, heat flow and geothermal gradients in Shelleng area and environs, northeastern Nigeria from aeromagnetic data

Abstract

Regional estimation of Curie-point depth (CPD), subsurface heat ow and geothermal gradients variations in the Shelleng area and environs of northeastern Nigeria was carried out in this study using spectral analysis of high-resolution aeromagnetic (HRAM) data. The HRAM data were divided into nine (9) overlapping blocks and each of the blocks was analyzed to obtain the 2D radially averaged power spectrum which enabled the computation of depths to the top and centroid of magnetic sources. The obtained values were then used to determine the depth to the bottom of magnetic bodies or the CPD, geothermal gradients and crustal heat ow changes in the study area. Results showed that CPD varies from 7.56 to 18.01 km, with an average of 11.72 km; geothermal gradient values vary between 32.20 and 76.72°C/km, with an average of 52.76°C/km, while heat ow variations range from 80.51 to 191.80 mW/m 2 , with an average of 131.85 mW/m 2 . Shallow CPD zones identi ed in the northeastern, western and southwestern portions of the study area correspond to zones of high geothermal gradient values and high subsurface heat ow distributions. These areas signify zones associated with anomalous subsurface thermal conditions and were therefore recommended for further detailed geothermal energy exploration studies.