Spectral analysis of aeromagnetic data for geothermal investigation of Wikki Warm Spring, north-east Nigeria

Spectral analysis of residual magnetic anomalies from aeromagnetic data has been used to estimate the Curie Point Depth (CPD) in the Wikki Warm Spring area of NE Nigeria which lies within the Upper Benue Trough. The CPD is that depth at which the dominant magnetic mineral in the crust passes from a ferromagnetic state to a paramagnetic state under the effect of increasing temperature (Nagata, 1961). This, along side the approximate Curie temperature for magnetite was used to infer the thermal gradient and hence the average heat flow in the area which is found to indicate anomalous geothermal conditions. This study confirms indications of crustal thinning in the Upper Benue Trough and suggestions that abnormally hot material can be found beneath the trough at comparably shallow depths. The Wikki Warm Spring area has a great energy potential with an estimated average CPD of 8 km, an average geothermal gradient of 68 °C/km and very high heat flow values (an average of 170 mW/m2). It has been shown that temperatures greater than 100 °C can be reached at depths of less than 2 km thus making the Wikki Warm Spring a promising area for exploration of geothermal resources.