Geochemistry, petrogenesis and geological implication of granitic rocks in Igarra area, southwestern Nigeria

Abstract

The Igarra area in southwestern Nigeria hosts a diverse suite of granitic rocks that play a significant role in understanding the regional geological framework. This study employs a comprehensive geochemical and petrogenetic approach to unravel these granitic rock’s origin, evolution and geological implications. A comprehensive geochemical analysis was conducted on samples of the granitoids. The results showed moderate to high SiO2, Na2O and K2O, with average compositions of 68.95%, 3.50% and 4.09%, respectively. The total alkalis are characterised by low MgO, CaO, TiO2 and P2O5, consistent with metaluminous to weak peraluminous compositions. The granite primarily falls within the high-K calc-alkaline region, exhibiting distinctive patterns in rare earth elements, with notable depletion in Nb, P and Ti. Geochemical modelling suggests that the granitoids originated from incomplete melting of metasedimentary source rocks under low to moderate pressure conditions, with limited crustal contamination. Trace element discrimination diagrams indicate a collisional tectonic setting for the Igarra granitoids, interpreted to have formed during continental collision. This mixed-source model suggests a complex magmatic system involving both crustal and mantle contributions, with potential interaction between these diverse melt components during the formation of the granites. This study offers fresh perspectives on the evolutional setting of the Igarra granitoids, understanding the geological effect of the Pan-African belt in Southwestern Nigeria and its broader implications.