GEOTHERMAL HEAT FLOW ANALYSIS OVER THE UPPER SOKOTO BASIN, NIGERIA USING AEROMAGNETIC DATA

Abstract

Geothermal Heat Flow Analysis over the Upper Sokoto Basin Nigeria, using Aeromagnetic Data was carried out to determine the geothermal heat flow in the area. The study area extends from latitude 12.50°N to 13.50°N and Longitude 4.00°E to 6.00°E. Polynomial fitting method was applied in the regional – residual separation from the digitised data. The observed magnetic residual anomalies map was Fourier transformed after dividing the area into 24 overlapping sections for spectral analysis and interpretation. The Spectral plot reveals two layers of magnetic sources. The Basement depth (D2) varies from 0.505 km to 1.77 km with an average value of 1.240 km, while the Centroid depth (D3) varies from 3.495 km to 8.110 km with an average of 4.763 km. Thus D3 values were used to obtain an approximate contour map of the basement surface in the basin. The curie - point depth estimated from the spectral analysis varies from 5.720 to 14.840 km with average of 8.285 km. Contour map of the curie- point depth and its corresponding 3-D Model were generated. The calculated geothermal gradient and heat flow for the study area varies between 20.216 to 52.447 oC/km and 36.388 to 94.405 mW/m2¬¬¬¬¬¬¬¬ respectively. The general trend shows that the area with the highest heat flow value (94.405 mW/m2) found in the north-eastern region of the study area correspond to the area with the highest geothermal gradient and vice-versa, also with shallow curie-point depth. This area is likely a geothermal source potential zone.