Electrical Resistivity Tomography Investigation of Coal Seam Geometry and Groundwater Occurrence in Enugu Coal Fields

The Enugu Coal Fields represent one of Nigeria's most significant coal deposits, yet detailed knowledge of seam geometry and associated groundwater systems remains limited due to the sparse application of modern geophysical methods. This study employs two-dimensional electrical resistivity tomography (ERT) to characterize coal seam geometry, delineate aquifer zones, and assess structural discontinuities within the Enugu Coal Fields. A total of twelve ERT profiles were acquired using the Wenner-Schlumberger electrode configuration, with maximum current electrode separations of 200 m. Data were inverted using RES2DINV software to generate subsurface resistivity models. Resistivity values below 10 ohm-m are interpreted as water-saturated zones within the Mamu Formation, while resistivity values exceeding 500 ohm-m correspond to coal seam occurrences. Coal seams are traced at depths of 15 m to 65 m across the study area, with thickness variations suggesting post-depositional faulting. Groundwater-bearing zones are identified at two distinct depth intervals, with the shallow aquifer system (8 to 25 m) appearing vulnerable to contamination from coal mining activities. Structural discontinuities inferred from resistivity contrasts in the tomographic sections are consistent with northeast-trending fault patterns previously mapped at the surface. These findings enhance the understanding of the subsurface architecture of the Enugu Coal Fields and provide data relevant to safe and sustainable mining operations. This study also highlights the role of ERT in minimizing hydrogeological risks associated with coal extraction in the region.

Keywords: electrical resistivity tomography, coal seam, Enugu Coal Fields, aquifer, Mamu Formation