Mapping of subsurface thermal structures of Gongola Basin, NE Nigeria from airborne magnetic and gamma-ray spectrometry data: implication for geothermal prospecting

The present study attempts to map the thermal structures of part of the Gongola Basin, NE Nigeria, from airborne magnetic and gamma-ray spectrometry data, with implications for geothermal resource exploration. The residual of the Total Magnetic Intensity (TMI) was subdivided into nine spectral overlapping blocks and subjected to spectral analysis to deduce the geothermal parameters, Curie point depth (CPD), geothermal gradient and heat flow (HF). Likewise, the varying concentrations of radioelements (K, eTh and eU) within the study area were used to estimate the radiogenic heat production (RHP). The results show that the CPD, geothermal gradient and HF range from ۱۷.۳۱–۴۶.۰۲ km, ۱۲.۶۰–۳۳.۵۱ oCkm-۱, and ۳۱.۶۳–۸۴.۱۰ mWm-۲ respectively. On the other hand, the radiogenic heat production (RHP) of K, eU, and eTh ranges from ۰.۰۰–۰.۰۱ µWm-۳ < ۰.۳ – ۴.۲ µWm-۳ < ۰.۴ –۷.۴ µWm-۳. While the total RHP ranges from ۰.۷ to ۷.۵ µWm-۳. The high RHP obtained in the northwest, west, and southwest flanks of the study area might be a result of the dominant crystalline rocks; while the high RHP observed in the southern part might be attributable to the Pindiga Formation, composed of shale, limestone, and sandstone, which is highly rich in uranium. The regions (central, northwest, southwest, and southeast) with HF > ۸۰ mWm-۲ and RHPs of ۲.۵ µWm-۳ and these meet the recommended values for good geothermal resources and could be considered good indicators for geothermal energy exploration in the study area.

کلیدواژه ها:

magnetic ، Gamma-ray Spectrometry ، radiogenic heat production ، thermal structure ، geothermal prospecting