Gravity and geothermal anomalies in Borno Basin, Nigeria
Some prominent geothermal anomalies are found occurring in association with gravity anomalies in the Borno basin. Similar gravity anomalies also occur in the Benue and Niger (Nupe) basins. Both the geothermal and gravity anomalies of Borno basin are trending NW-SE similar to the Niger (Nupe) basin, while the Benue Trough gravity anomalies trend NE-SW. This paper briefly attempts the interpretation of the gravity anomalies to provide explanations to the origin of the corresponding geothermal anomalies in Borno basin. The work also serves for a position paper on the aspects of the relevance of gravity data to geodynamics in the exploration for geothermal energy as an additional source of energy for Nigeria. Results of interpretation of gravity data show that the Borno basin geothermal anomalies are caused by uplifted upper mantle (thinned crust) to the depth range of 22 to 26 km. These anomalous lithospheric structures identified along three (3) profiles across the anomalies are considered to represent a hot (not well-consolidated) upper mantle under the basin. The hot zone material, as a geothermal reservoir could provide the heat sources conducting in contact with groundwater in the deep faults bounding the graben-horst structures occurring at depth ranges within 1-10 km, also deduced from the gravity data.
Keywords: Gravity, Geotherm, Lithospheric Structures, Energy, Borno Basin.