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The widespread occurrence of geothermal manifestations in Nigeria is significant because the wide applicability and relative ease of exploitation of geothermal energy is of vital importance to an industrializing nation like Nigeria. There are two known geothermal resource areas (KGRAs) in Nigeria: the Ikogosi Warm Springs of Ondo State and the Wikki Warm Springs of Bauchi State. These surficial effusions result from the circulation of water to great depths through faults in the basement complex rocks of the area. Within sedimentary areas, high geothermal gradient trends are identified in the Lagos subbasin, the Okitipupa ridge, the Auchi-Agbede area of the Benin flank/hinge line, and the Abakaliki anticlinorium. The deeper Cretaceous and Tertiary sequences of the Niger de ta are geopressured geothermal horizons. In the Benue foldbelt, extending from the Abakaliki anticlinorium to the Keana anticline and the Zambuk ridge, several magmatic intrusions emplaced during the Late Cretaceous line the axis of the Benue trough. Positive Bouguer gravity anomalies also parallel this trough and are interpreted to indicate shallow mantle. Parts of this belt and the Ikom, the Jos plateau, Bauchi plateau, and the Adamawa areas, experienced Cenozoic volcanism and magmatism.
Geothermal gradients indicate that steam would be encountered at a depth of about 6,000 ft (1,800 m) in the Lagos and Auchi-Agbede areas, and at about 4,250 ft (1,300 m) in the Abakaliki area. A combination of heat-flow measurements and analysis of existing aeromagnetic data would provide a basis for the determination of geothermal gradients in the undrilled resource areas and the determination of depths to Curie isogeotherm (about 570°C, 1,058°F) in the basement complex and the intrusive areas from thermal attenuation of the remanent magnetic field. The separate but preferably combined application of gravity analysis, and electrical, refraction-seismic, electromagnetic, and telluric methods would help in the accurate delineation and evaluation of Nigeria's known and suspect d geothermal resource areas for future detailed investigations and possible exploitation.
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