Peter Oluwanishola Mafimisebi

Geochemical analysis of eight (8) representative pegmatite samples reveals high silica (SiO2) 56-62.05 wt % and alumina (Al2O3) 6.80-8.39 wt % contents. The alumina (Al2O3) is greater than the alkali Na2O + K2O +CaO in all the rock samples by values ranging between 0.79 and 1.25wt % implying that the rocks are peraluminous. MgO (0.00-0.00wt%), CaO (1.65-1.86wt %) and Fe2O3 (2.89-3.86 wt %) have low contents. Paleo-weathering plot reveals a moderate humid climatic condition and the mean values of CIA (45.15), CIW (81.00), PIA (11.32) and indicates low to high chemical weathering in the source area. Rocks that are characterized by low Mg, Ca, and Fe as well as low ratio of Na2O/K2O are termed “fertile” and peraluminous. A plot of Al2O3/ (CaO + Na2O + K2O) versus Al2O3/Na2O + K2O shows and confirms the peraluminous character of the pegmatite from Oke-Ode. Rocks that are fertile and peraluminous are rich in albite (NaAlSi3O8), potassium feldspar (KAlSi3O8) and quartz (SiO2). The abundance of feldspar and mica are geochemical indicators for Sn-Ta mineralization. The plotting of samples in both the tholeiitic and calc-alkaline fields shows that the magma from which the pegmatite was formed was not totally restricted in occurrence only to subduction-related environment but also from the oceanic crust of calc-alkaline environments. The trace elements such as of As, Mo, Rb and Zn with an average of 5.33ppm, 28.00ppm, 145.22ppm, and 24.89ppm, respectively shows that they are above the abundance level in common rocks. This indicates that the As, Mo, Rb, and Zn are abundant in all the samples of the study area.