Appraisal of the magnetic and geothermal anomalies of bornu basin northeast nigeria involving aero-magnetic data

Abstract

The Bornu Basin in northeast Nigeria was studied using high-resolution airborne magnetic data with the objective of improving the reliability of mapped magnetic and geothermal anomalies, and depth solutions. Necessary enhancement operations like analytic signal (ASIG), upward continuation, depth assessment methods involving standard Euler deconvolution (SED) and source parameter imaging (SPI) as well as spectral analysis applying the centroid technique were applied. The middle and southern parts are dominated by high frequency anomalies as revealed by the ASIG map. Furthermore, the magnetic data, when upward continued to 5 km, revealed avalanche of deeply buried igneous intrusions that created near-surface magnetic sources and geologic structures. Maximum thicknesses of sedimentary series estimated from SED and SPI, are respectively ~5974.7 and ~5885.3 m. These values correlate correlated relatively well with depth to the top boundary (Z_t) of ~6550 m obtained from the centroid technique. These depth estimates reveal sequence of thick sediments overlying igneous intrusions and falls under the prospective geothermal anomaly zones characterised by high geothermal gradient (GG) (>55 °C/km) and heat flow (HF) (>130 mW/m²) values. Areas characterised by high geothermal anomalies correspond to igneous intrusion-dominated shallow Curie point depths (CPD or Zb).