An Integrated Geophysical Approach for the Precise Delineation of Sulphide Ore Within Fractured Zones of the Southern Benue Trough, Southeastern Nigeria

ABSTRACT Given the need to reduce the proliferation of abortive mines, delineate the frontiers of the mineralised zone, and prioritise the presiding structural attributes of the sulphide ore deposits within the Benue Trough, this study integrated electrical resistivity tomography (ERT), induced polarisation (IP) and ground magnetic methods to characterise the litho‐structural attributes significant for precise delineation of the lead‐zinc deposits hosted by the fractured sedimentary rocks. The magnetic result delineated the major structural framework constituting NE–SW, NW–SE, N–S and E–W with the dominance of NE–SW and NW‐SE structures dipping easterly and westerly, respectively. Their interpolation with the active‐productive mines designated NW‐SE structures trending ≥ 300° N with a high dip of up to 60°, and a few N–S structures to be mineralised. High magnetic anomaly closures predominantly trending in the NE–SW direction corresponded with mapped basic‐intermediate intrusive rocks in the area. These structural trends guided the layout of the ERT and IP profiles in the E–W direction. In the mineralised zones, the ERT and IP signals indicated significantly low resistivity and high chargeability values, whereas the host rock exhibited high resistivity and poor chargeability responses. The ERT and IP signatures further characterised two main ore horizons and zoning: the shallow and deep emplaced lodes with average depths of 35 and 60 m, respectively. The 2D and 3D models revealed subsurface inhomogeneity and conduit‐like geometry of the orebody corresponding to NW‐SE trending structures. The mineral zoning and complex structural framework observed in the area suggest variable thermal regimes, micro‐alteration in hydrothermal fluid composition and polyphase tectonic‐magmatic activities in the Benue Trough.