Interpretation of Aeromagnetic and Geochemical Data for Tectonic and Structural Setting of Granitic Rocks Around Bishewa Area, Southwestern Nigeria
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Date
2022
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Springer
Abstract
High resolution aeromagnetic data of Bishewa area has been analysed to establish the geometry of its lithologic settings. Magnetic residualization of the total magnetic intensity (TMI) and derivative of resulting magnetic anomalies were enhanced using the fast Fourier transform of Oasis montaj geo-software. The reduced-to-equator residual anomaly varies within -174.9 to 111.9 nT which revealed the contrasting lithologic units viz: sedimentary and basement complex. The negative magnetic intensities (lows) in the southern and sparsely within the northwestern regions are associated with rocks of lower content of ferromagnetic minerals and are attributable to underlying igneous and metamorphic rocks or intrusive bodies within the schist. The positive anomalies coincide with the predominant migmatite gneiss complex. Structural relationships between the granites and metasedimentary host rocks suggest that the emplacement of the granitoids are associated with early, large-scale thermotectonic regional deformation within the Nigerian basement complex. It also revealed a transpressional regime that is characterized by WNW-ESE shortening and large-scale sinistral strike-slip faults associated with the regional NE-SW structural grains in the basement rocks of the area. Regional geologic features and structural correlation show that the area is underlain by the northwestern extension of the Ilesha schist belt in the western sector of the Nigerian basement complex.