Integration of magnetic and remote sensing methods for mapping geothermal signatures in the middle part of Benue Trough, Northeastern Nigeria

Abstract

The Middle part of Benue Trough is one of the notable regions with geothermal manifestations in Nigeria, which is evident in the form of warm springs and mud pots. In this study, aeromagnetic and remote sensing data were utilized to evaluate the deep-seated and surface signatures of the geothermal system in the middle part of the Benue Trough. The analysis of aeromagnetic data involves the application of the reduction-to-pole (RTP) technique on total magnetic intensity (TMI) anomaly data to reposition anomalies above their magnetic sources. Filters were subsequently applied on the RTP map to suppress artefacts and anomalies produced by shallow magnetic sources. Additionally, the day-time land surface temperature (LST) of the study area was derived using Landsat-8 data. ASTER day-time and night-time images were subsequently used for detailed thermal anomaly mapping of a subset of the study area with elevated temperature in the Landsat derived LST. The STcorr algorithm was employed for the correction of topographic influences and generation of thermal anomaly maps from day-time and night-time ASTER data. Analysis of aeromagnetic data revealed that some of the geothermal manifestations within the study area are linked to deep-seated structures while others are related with the intrusive rocks. Generally, Akiri, Awe, Azara, and Ribi thermal springs display noticeable thermal anomalies in the night-time thermal anomaly map with the Akiri thermal spring having the most prominent thermal anomalies. The Ribi, Azara, and Akiri thermal springs, which are linked with deep-seated structures exhibit higher temperatures than Keana and Awe thermal springs, which are thought to be associated with intrusive rocks in the day-time LST and thermal anomaly images. The integration of geophysical and remote sensing data for the exploration of geothermal resources adopted in this study offers a rapid and cost-effective approach that can be adapted for geothermal resource exploration in other areas suspected to have blind geothermal systems with minimal surface manifestation.