Metamorphic processes during the Proterozoic era, undoubtedly, played significant roles in shaping the mineralized schist belts within the polycyclic Precambrian basement complex of southwest Nigeria. This study investigated the petrological, geochemical characteristics and tectonic setting of quartz biotite schist in Falansa, south of Oyan-Iseyin-Ibadan schist belt, using field, petrographic and geochemical data. Field evidence indicates that the quartz biotite schist shared lithologic boundaries with the quartz schist, granite, and aplite. The schistose bodies served as host to many of the beryl-bearing pegmatite intrusions and share boundary with the granitic-gneiss. Petrographic analysis on the quartz biotite schist revealed a mineral assemblage, quartz + muscovite + biotite + plagioclase typical of greenschist facies condition of metamorphism. Results of the geochemical analysis showed high and moderate enrichments in SiO2 (av. 58.73%) and Al2O3 (av. 15.83%), respectively. Molar A/CNK values are greater than 1.2 and ACF diagram suggest an alumina rich pelitic protolith. Trace element data showed that the quartz biotite schist is rich in rare metals (Be, Rb, Ta, REE) over upper crustal values of Taylor and MacLennan. Rare earth element (REE) compositions suggest light rare earth elements (LREEs) enrichment. Variable Nb/Ta ratio, mostly lower than the average upper continental crust value of 12, implied possible heterogeneous protolith source while ratios of Th/Sc, Zr/Sc La/Sc and trilinear plot of La-Th-Sc suggest reworked crustal precursors from continental island arc environment.
Jimoh et al. (Sun,) studied this question.