The Geochemistry and Petrogenesis of the Kofayi Younger Granite Complex, Central Nigeria

The Kofayi Younger Granite Complex is one of the fifty three (53) anorogenic granite suite in Nigeria which intruded the Precambrian Basement Complex. The complex is found to comprise of felsic rocks like; biotite-granites, biotite micro granites, hornblende and biotite granites. The complex is also found to be associated with mafic rocks like diorites which, at some portions have formed hybrid rocks. The geochemistry of sixteen (16) representative rock samples was carried out on the energy dispersive xray fluorescence (EDXRF) for twelve (12) major and thirty seven (37) trace and REE elements. Agpaitic index and alumina saturation index suggest that the rocks are peraluminous. The widely used SiO2 vs K2O classify most of the granite samples as high K rocks while the mafic diorites are calc-alkaline. Discrimination diagrams for tectonic interpretation of granitic rocks ((Na2+K2O)/CaO vs Zr+Nb+Ce+Y and Nb vs Y, suggest that all the samples are WPG, as well as A-type granites. The enrichment of high field strength (HFS) elements in the investigated granites confirms their A-type identity and exclude them from other granitic types. Spidergraph show negative Sr anomaly suggesting the feldspar fractionated nature of the granitoids where plagioclase played an important role in the evolution of the A-type magmatism. The magma that gave rise to the granitoids most likely came from the lithospheric mantle.The enrichment of Zr and Nb in the rocks indicate Nb-Sn-W mineralization. The northern part of the Complex contains Pb>15 which confirms that it are tin-bearing or productive granitoid suite.