Geochemistry of selected pegmatites from Olokuta and Onibembe areas, Ikire, Osun State, Southwestern Nigeria: Mineralization and tectonic setting implications

Whole rock geochemical analysis was carried out on eight (8) representative samples of pegmatites collected from the Olokuta and Onibembe pegmatites, Ikire, Osun State. These samples were analyzed for major, trace and rare earth elements using the inductively coupled plasma-mass spectrometer (ICP-MS) technique. This analysis was done to assess the mineralization potentials and tectonic setting of the pegmatites at the time of emplacement. The pegmatites were rich in K2O and moderately to strongly peraluminous with the Onibembe pegmatites being more aluminous. The K/Rb ratios and plot of K/Rb vs. Rb showed that the pegmatites were barren with low mineralization potentials. However, the Onibembe pegmatites were more enriched in Cs, Be, Ga, Sn, Nb, Ta, Th, U, W, and Zr relative to the Olokuta pegmatites. The tectonic settings discrimination plots for the pegmatites showed that they were emplaced within a syn-collisional environment. The chondrite-normalized rare earth elements (REEs) pattern showed that the Olokuta and Onibembe pegmatites were crystallized from different magmas. The geochemical characteristics of the Onibembe pegmatites indicated higher fractionation relative to the Olokuta pegmatites.