Spectral Analysis of Aeromagnetic Data for Curie Point Depth Estimation in Northern Nigeria

This study applies spectral analysis of aeromagnetic data to estimate Curie point depth variation across northern Nigeria, providing geothermal gradient constraints relevant to energy resource assessment and tectonic interpretation. The Curie point depth is the depth at which rocks lose ferromagnetism due to temperature effects, and its estimation from the spectral properties of aeromagnetic anomalies provides a proxy for crustal thermal structure. Northern Nigeria's geothermal potential is poorly characterised, and Curie depth mapping from existing aeromagnetic datasets offers a cost-effective first-pass geothermal assessment tool. This study processes a compilation of NGSA aeromagnetic data for northern Nigeria covering 240 1:100,000 map sheets from Kebbi to Borno States. Data are compiled into a seamless grid and processed for IGRF removal and microlevelling. Spectral analysis uses the centroid method and the forward difference method applied in overlapping 100 by 100 kilometre windows to estimate Curie point depth across the region. Curie depth maps are produced at 50-kilometre resolution and converted to heat flow estimates using appropriate geothermal gradients. Findings reveal Curie point depths ranging from 18 to 38 kilometres across northern Nigeria, with the shallowest values concentrated in the Lake Chad Basin area (18 to 24 kilometres) indicating higher-than-average heat flow. The Jos Plateau volcanic complex shows Curie depths of 20 to 25 kilometres, consistent with Mesozoic-Tertiary magmatic activity. Deep Curie values of 34 to 38 kilometres beneath the basement complex in Kogi and Kwara States indicate cold, stable cratonic lithosphere. The study provides the first regional Curie depth map for northern Nigeria and identifies the Chad Basin as a priority area for geothermal energy exploration.

Keywords: Curie point depth, aeromagnetic spectral analysis, geothermal gradient, northern Nigeria, heat flow.