Geology and Rare Earth Element Geochemistry of Magnesian Granitoids Within Proterozoic Schist Belt of Southwest Nigeria

The increased global demand for and price of rare earth elements (REEs) has led to intensive search for them in rocks of the upper continental crust all over the world. This study is aimed at characterising the granitoids at Okeho within Southwestern Nigeria using geochemical data and assessing their potential for REE enrichment. Ten representative rock samples of the Proterozoic intrusives, syenite and granodiorite, were studied for their mineralogical and elemental compositions. Elemental concentrations were analysed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS).

Average major oxide concentrations revealed SiO₂ (57.53 wt. %), Al₂O₃ (13.25 wt. %), CaO (5.05 wt. %), and MgO (5.59 wt. %) for the syenite and SiO₂ (62.39 wt. %), Al₂O₃ (14.98 wt. %), CaO (3.67 wt. %), and MgO (3.25 wt. %) for the granodiorite. Total Alkali–Silica (TAS), Aluminum Saturation Index (ASI), and La/10-Y/15-Nb/8 plots discriminated the granitoids as metaluminous monzonite-syenite and peraluminous diorite-granodiorite. Average total REE concentrations in the syenite (625.06 ppm) and porphyritic-granodiorite (364.51 ppm) were above values reported for the granites in some mines in Jiangxi Province, Southern China.