Major oxide geochemistry and petrogenetic implications of Pan-African rocks around Omi-Olori, Ado-Ekiti Area, Southwestern, Nigeria

This study presents whole-rock major oxide geochemical data for selected Pan-African basement rocks from the Omi-Olori area, Ado–Ekiti, southwestern Nigeria, with the aim of constraining their petrogenesis, magma evolution, and tectonic setting. The investigated lithologies include biotite granite, leucogranite, and granitic gneiss, diorite, and charnockitic rocks. The geochemical results reveal silica-rich granitoids (SiO₂, 67–72 wt.%) contrasted with intermediate to mafic compositions in dioritic and charnockitic rocks (SiO₂, 50–59 wt.%). Harker variation trends indicate systematic decreases in Fe₂O₃, MgO, CaO, and TiO₂ with increasing SiO₂, suggesting fractional crystallization as a dominant magmatic process. Alumina saturation indices (A/NK) vs (A/CNK) show that the granitoids are predominantly peraluminous to weakly metaluminous, indicating significant crustal contributions, whereas the diorites and charnockitic rocks exhibit near-metaluminous signatures, reflecting mantle influence. The AFM diagram defines a calc-alkaline trend, consistent with magmatism in a convergent to collisional tectonic setting. Petrogenetically, the rocks represent a genetically related suite involving mantle-derived dioritic magmas, crustal anatexis producing granites and leucogranites, and high-temperature deep crustal processes responsible for charnockitic rocks formation. These features are consistent with magmatic evolution during the Pan-African orogeny. The study provides insights into crust–mantle interaction and contributes to the understanding of basement evolution within the Nigerian segment of the Trans-Saharan Belt.

Keywords: Pan African orogeny, basement complex, major oxides, petrogenesis, Ado–Ekiti.