Characterization and mineralization potentials of granitic pegmatites of Komu area, southwestern Nigeria

Abstract

The geology of the Komu area, south-western Nigeria was investigated in order to determine the nature of occurrence, petrography and chemical composition, and to evaluate the mineral potential of granitic pegmatites. The pegmatites are hosted by para-gneisses, amphibolites and granitic rocks. These host rocks are characterized by low pressure mineral assemblages of upper greenschist to lower amphibolite facies grades. The pegmatites consist of four lithological units: alkali feldspar unit, graphic granite unit, quartz-albite-muscovite-tourmaline unit and saccharroidal albite-muscovite-tourmaline-garnet unit.A K/Rb ratio of below 100 is indicative of a mineralization potential in most pegmatites, except for the saccharroidal albite-muscovite-tourmaline-garnet unit which has exceptionally high ratios. The discrimination diagrams Rb versus K/Rb, Zn versus K/Rb and Th versus K/Rb show a limited range of fractionation, suggesting that the pegmatites belong to the barren muscovite and rare element classes. The rare element class is moderately enriched in beryl, tourmaline and niobium-tantalum minerals. The pegmatite has affinity for beryl columbite sub-type and lithium-cesium-tantalum (LCT) family. The ores plot mainly in the field of mangano-tantalite of tantalite-columbite quadrilateral diagram. These results indicate that the pegmatites are promising hosts for Nb-Ta ores. © 2010 The Authors. Journal compilation © 2010 The Society of Resource Geology.