Determination of depths to magnetic sources within Abakaliki–Afikpo area and environs, Southeastern Nigeria: implications for mineral and hydrocarbon prospectivity

Abstract

There have been repeated calls from various quarters in Nigeria for a robust examination of Abakaliki anticlinorium and Afikpo sub-basin of the Southern Benue Trough for their mineral and hydrocarbon prospects. The Southern Benue Trough is part of a linear NE-SW trending rift system whose development is related to the breakaway of Africa from South America and the subsequent opening of the South Atlantic Ocean during the Cretaceous. Detailed geophysical studies were carried out with the high resolution aeromagnetic data using analytical techniques which include spectral analysis, analytic signal (AS) evaluations, Euler deconvolution, potential field transformation and two-dimensional potential field modelling of subsurface geology. Results reveal varying depths ranging from 0.41 to 0.67 km for depths to magnetic sources, and 1.0–5.5 km for basement depths. The presence of magnetic sources within the sedimentary basins is indicated by shallow depths to the top (DTT) of magnetic sources. Euler depth estimates ranging between 1.0 and 4.8 km for the magnetic source contacts/faults concurs with depths to the basement of between 4.5 and 4.9 km realised from the 2D modelling. Euler deconvolution of the magnetic anomalies also revealed the presence of Sill and Dyke structures at Amuzu, Enyigba, parts of Abakaliki, Utampa, Abriba, Afikpo, Ugep, and Agoi Ekpo regions with varying depths of up to 3.5 km. Structures mapped around Okposi, Amuzu, Enyigba Abakaliki, and Ishieke areas present viable prospects for hydrocarbon exploration. Structures identified at the Afikpo region could best represent mineral lode within the area. The 2D modelling shows various subsurface geological structures to include faults, fractures, sill, dyke, and considerable basement intrusion within the profile. Results from this study have identified an expanse of untapped areas with higher prospectivity which could be exploited for productive and viable mineral and hydrocarbon explorations.