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An estimate of Curie-point isotherm depths has been made in the northern part of the Nupe Basin, west of Central Nigeria, from the spectral analysis of aeromagnetic data. Curie-point, the temperature at which rocks lose their ferromagnetic properties, provides a link between thermal models and models based on the analysis of magnetic sources. The result of this study shows that the Curie isotherm depth varies between 12 and 30km in the study area. In the southern portion of the study area, the curie-depth was found above 28km while it was found to be less than 14km in the northern part. It had previously been discovered by earlier workers that Curie-point depths are shallower than 15km for volcanic and geothermal fields, between 15-25km for island arcs and ridges, and deeper than 20km in plateaus and trenches. Therefore, when the values for the study area are compared with these values, the areas with variations less than 15km maybe recommended for further geothermal reconnaissance studies.

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Abstract.A regional estimation of Curie-point depths (CPDs) and succeeding geothermal gradients and subsurface crustal heat flow has been carried out from the spectral centroid analysis of the recently acquired highresolution aeromagnetic (HRAM) data of the entire Bida Basin in north-central Nigeria. The HRAM data were divided into 28 overlapping blocks, and each block was analysed to obtain depths to the top, centroid, and bottom of the magnetic sources. The depth values were then used to assess the CPD, geothermal gradient, and subsurface crustal heat flow in the basin. The result shows that the CPD varies between 15.57 and 29.62 km with an average of 21.65 km, the geothermal gradient varies between 19.58 and 37.25 • C km −1 with an average of 27.25 • C km −1 , and the crustal heat flow varies between 48.41 and 93.12 mW m −2 with an average of 68.80 mW m −2 . Geodynamic processes are mainly controlled by the thermal structure of the Earth's crust; therefore this study is important for appraisal of the geo-processes, rheology, and understanding of the heat flow variations in the Bida Basin, north-central Nigeria.

Background: The recent paper by Abraham et al. (2014) 'Spectral analysis of aeromagnetic data for geothermal energy investigation of Ikogosi Warm Spring -Ekiti State, southwestern Nigeria' applied spectral analysis in the interpretation of aeromagnetic data for estimation of curie-point depths using a data window of 55 × 55 km; however, the employment of such small window may not be consistent with derived curie-point depth results. Discussion: Here, I would like to clarify and point out the possible errors in the paper.