Geophysical investigation of the possible extension of Ifewara fault zone beyond Ilesa area, southwestern Nigeria
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ORIGINAL PAPER
Geophysical investigation of the possible extension of Ifewara fault zone beyond Ilesa area, southwestern Nigeria Musa Olufemi Awoyemi 1 & Olayide Sakirudeen Hammed 2 & Sesan Cornelius Falade 1 & Augustine Babatunde Arogundade 1 & Ojudoo Darius Ajama 1 & Peter Olatunde Iwalehin 1 & Oluwaseun Tolulope Olurin 3
Received: 19 May 2016 / Accepted: 20 December 2016 # Saudi Society for Geosciences 2017
Abstract High-resolution aeromagnetic data (HRAD) of parts of the southwestern and north-central Nigeria between 7° 30′ N – 8° 30′ N and 4° 30′ E – 5° 30′ E have been analyzed with a view to investigate the possible extension of Ifewara fault zone beyond Ilesa area. Analyses of the filtered HRAD by analytic signal amplitude (ASA), horizontal gradient magnitude (HGM), first vertical derivative (FVD), and Euler deconvolution (ED) methods were combined to delineate the locations, strikes, and dip directions of the subsurface structures in the area. The inferred structural map and the associated rose diagram indicate that the area is bisected by a number of major and minor faults that trend NE-SW, ENE-WSW, EW, NW-SE, WNW-ESE, NNE-SSW, and NNW-SSE, among which the NE-SW trending faults predominate. The Ifewara and other major fault zones were clearly delineated. The mapped Ifewara faults trend between NNE-SSW and NESW directions and extend from the southwestern part (Ilesa area) to the extreme of north-eastern part of the study area. The study concluded that the Ifewara fault zones exist and do not terminate in the southwestern part of Nigeria but further extends to the northern part, possibly to Nupe basin and Zungeru area. Keywords Ifewara . Zungeru . Fault . Abut . Belt . Craton . Fracture zone * Musa Olufemi Awoyemi [email protected]
1
Department of Physics and Engineering Physics, Obafemi Awolowo University, Ile-Ife, Nigeria
2
Department of Physics, Federal University Oye Ekiti, Oye-Ekiti, Nigeria
3
Federal University of Agriculture, Abeokuta, Nigeria
Introduction The African plate, as a part of Gondwana and Pangea, is considered the third largest tectonic plate (~60 million km2) and half of it is covered by land (Gaina et al. 2013). The African plate comprises of several old cratonic units and accreted younger crust, representing a period of more than 2.5 billion years of continental and oceanic crust growth (Gaina et al. 2013). The cratons, which are the Kalahari craton, Congo craton, Tanzania craton, and West African craton, are widely separated in the past but came together during the Pan-African orogeny and stayed together when Gondwana split up. The cratons are connected by orogenic belts (regions of highly deformed rock where the tectonic plates have engaged). The geological framework of Nigeria is located within the mobile belt of Africa between the West Africa craton and the Congo craton. The Pan-African orogeny that occurred 600 ± 100 Ma was the last major deformation and metamorphism experienced within the belt with slight effect on the adjacent craton (Turner et al. 1971; Tsalha et al
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