Geological Mapping and Petrostructural Characterization of Precambrian Rocks in Oke-Ode Area, Southwestern Nigeria: Implications for Regional Tectonics and Geological Evolution

This study presents a comprehensive petrostructural investigation and geological mapping of the Oke-Ode region, southwestern Nigerian Basement Complex. To comprehend the mode of occurrence and field relationship of the crystalline rocks, a systematic geological mapping of the rocks was carried out. Representative samples of the various types of rocks that were encountered were chosen for petrographic examination. The study area is characterized by diverse lithological units including quartzite, schist, granite, granodiorite and pegmatite as revealed by lithological mapping and field investigations, which also demonstrated polyphase deformation and intrusive linkages. According to petrographic assemblages, the rocks are made up of different amounts of quartz, microcline, plagioclase, muscovite, and biotite indicating amphibolite to granulite facies metamorphism, with evidence of partial melting and anatexis in migmatitic units. The geological map provides comprehensive insights into the complex lithological relationships, structural patterns, and geological features that record a prolonged history of deformation, metamorphism, and magmatic processes. Structural analysis reveals predominantly NE-SW to NW-SE trending foliations and joint systems, consistent with Pan-African orogenic compression. To interpret subsurface relationships, two structural cross-sections (A–A′ and B–B′) were built. The intrusive event in the area is believed to be of Pan-African age which is similar events throughout the Basement Complex of southwestern Nigeria. A complicated history of sedimentation, regional metamorphism, granitic intrusions, and subsequent tectonic uplift is suggested by the sequence of tectono-metamorphic events. The findings provide insights into the crustal evolution processes of rocks in the study area and is consistent with current theories of the Pan-African orogeny. This also advances the understanding of the geological evolution of Nigeria's Precambrian basement.