ABSTRACT

In order to identify the mineral prospects and potential for geothermal energy in the Lower Benue Trough South-Eastern Nigeria, through the determination of heat flow, geothermal gradient and the sedimentary thickness of the subsurface materials. Nine sheets of high resolution aeromagnetic data were used (Sheet 287 Nsukka, Sheet 288 Igunmale, Sheet 289 Ejekwe, Sheet 301 Udi, sheet 302 Nkalagu, Sheet 303 Abakaliki, sheet 312 Okigwe, sheet 313 Afikpo and sheet 314 Ugep). These sheets were merged into one composite sheet. The total magnetic intensity map, depth to basement maps, gradient maps, heat flow maps were produced through quantitative analysis. The result of the analysis shows that the magnetic intensity value ranges from -47.3 nT to 151 nT, and this is observed in the northern part near Bende with a prominent NE-SW trending Long wavelength anomaly shape. The Total magnetic intensity map of the area was reduced to the magnetic equator, this is because the area of the acquired data is along the equatorial zone. The reduction to equator (RTE) map ranges in value from -34.84 to 135.26 nT, the areas with high observed intensity (pink coloration) are around Okigwe, Isuikwua, Afikpo area (SW part of the composite map) and the areas west of Nsukka, low magnetic intensity was observed in the areas near Udi (western part of the composite map) and Eastern part of Igunmale, Ayamelum and the northern part of Nsukka (Blue coloration), the RTE map comprised of both the regional and the residual anomaly. the regional anomaly map shows variation in magnetic intensity values from 28.3 to 77.7 nT. The regional anomaly map also shows the regional trends of the area as observed trend is in the NE-SW and E-W. The residual anomaly map ranges in intensity value from -13.866 nT to 7.550 nT. This ranges shows the variation of these values within a short ranges. In all, it is confirmed that the occurrence of igneous bodies outcrops covered by thin overburdens within these areas also estimated the depth to basement to range from 2.2 to 4.8 km. The Heat flow calculated over the area of study shows variation from one place to another, these values range from 103.83 mW/m2 to 254.4 mW/m2 with an average value of 167.5 mW/m2. The geothermal gradient value of the area ranges from 42 to 102 OC/km with an average of 73 oC/km. The curie depth value for the area ranges from 5.6 km to a depth of 13.5 km, and average depth of 8.8 km. In conclusion, the use of remotely sensed (Airborne) magnetic data might not provide the 100 percent accuracy required to estimate the exact geothermal gradient and the heat flow, hence a test hydrocarbon well can be sunk and further geophysical and geochemical exploration is highly required.