3D modelling of subsurface features in parts of the Lower Benue Trough, south-eastern Nigeria, with high resolution aeromagnetic data

Abstract

Aeromagnetic data over Nsukka, Igumale, Udi, and Nkalagu has been interpreted qualitatively by enhancement processes namely: regional-residual separation, upward continuation, second vertical derivative, second horizontal derivative, and analytical signal with Oasis montaj 8.3 software. Quantitatively the data was analyzed and interpreted by forward modelling method. Rectangular prism was used as the simple geometric body in the model with potent 4.15.05 software. The results of the qualitative interpretation revealed deep sources within the study area on upward continuation at different heights; the shallow sources and geologic boundaries were delineated by the second vertical derivative map and second horizontal derivative map; the analytical signal revealed the faults within the study area. In terms of quantitative interpretation, the model revealed faults, fold, fracture zones between identical geologic sources, intercalated geologic sources, batholith structures and intruded bodies which suggest high potential zones of mineralization. Also the emplaced bodies in the model have depth to basement values between 2 and 8 km within the sediments, igneous or metamorphic basement. The magnetic susceptibility of most bodies suggested igneous intrusions with a few bodies attributed to metamorphic rocks and implied minerals such as schist, hematite, limonite, pyrite, pyrrhotite, chromite, porphyry, gabbro, basalt, and dolorite, most of which are iron rich.