Petrochemical Evaluations of the Pan African Pegmatites of Apomu Area, Southwestern Nigeria

Abstract

Pan African pegmatites occurring as near vertical dykes and striking mainly in the NNW-SSE direction have been studied in Apomu area with a view to evaluate their petrochemical features and possible economic potentials. These pegmatites intrude into the older lithology of granite around Apomu area Southwestern Nigeria. Petrographic determinations show they are composed of microcline, quartz and to a lesser extent plagioclase albite with interstitial muscovite, biotite and accessory minerals under transmitted light. A total of eleven samples comprising whole rock pegmatites were analyzed for major and trace elements using Inductively Coupled Plasma-Atomic Emission Spectrometry analytical technique (ICP-AES). From the geochemical results, the whole rock pegmatite is considerably siliceous, with an average value of 69.31%, while, MnO with a range of (0.01-0.23%), TiO2 with a range of (0.01-0.69%), P2O5 with a range of (0.02-0.23%) has values that are generally low. Mean contents of major oxides, Al2O3 (14.34% ), Na2O (3.31%), Fe2O3 (2.61%), MgO (0.78%), CaO (1.63%), and K2O (4.80%) for the Apomu pegmatites compare favorably with the Ipetu Ijesha barren pegmatites , Kafin Maiyaki barren pegmatites and Ago-Iwoye barren pegmatites. Apomu pegmatites are fairly enriched in Rb, Sr, Zr but comparatively, poor in the rare metals Ta, Nb, Cs and Sn. Rare metal mineralization enrichment indices mainly, Ta vs Nb, Ta vs K/Cs, plots, suggests the Apomu pegmatites to be barren in rare-metal mineralization when compared with other rare-metal pegmatites across the world.