Aeromagnetic perspectives on basement morphology and depth beneath Ilorin metropolis, Southwestern Nigeria

Abstract

The basement depths of the potential areas for mineral exploration were estimated in this study with the aid of aeromagnetic method. The data was obtained from the Nigerian Geological Survey Agency (NGSA) covering a total area of 55.5 km by 55.5 km between longitudes 4°30’E to 5°00’E to latitudes 8°00’N to 8°30’N of the topographic sheet 223-Ilorin.  The data were subjected to 2-D spectral filtering technique to determine the shallow and deeper depths of possible areas for exploration using Oasis Montaj™ software. The Total Magnetic Intensity (TMI) grid was first Reduced to Equator (RTE) to align magnetic anomalies with their source bodies. Subsequently, the RTE-TMI map was divided into 36 spectral sections. Digitization of the dataset was carried out on a 3 km by 3 km grid, with a spacing of 3 km, resulting in a Nyquist frequency of 0.167 km⁻¹ and 7,921 total data points. The results revealed a two-depth source model, identifying both deeper and shallower sources. The magnetic bodies at shallow depths of 0.12 to 0.49 km averaging 0.27 km near Edidi, Oko Erin and the northern part of Ila Orogun are probably related to basement features such as faults, joints and fractures which might serve as conduit for mineralization of the area. The depth of deeper magnetic bodies in Aremu, Oyan and northern Afon varies from 0.25 km to 1.76 km with an average of 1.24 km. The potential mineralization areas could be investigated further using ground truthing and geochemical analysis.