Petrographic Investigation of Oke-Awun Rocks, Southwestern Nigeria

Abstract

The Oke-Awun area is underlain by older units of Migmatitic gneisses, Augen gneisses, Quartz-biotitemuscovite schists, Quartzites and Amphibolites which have been intruded by Granites, Granodiorites and Pegmatites of probable Pan African (ca 600 Ma) age. The Gneisses are medium grained rocks with mineral constituent which include quartz, plagioclase, biotite, hornblende, microcline with accessory minerals such as chlorite, sericite, sphene, epidote and ore minerals. Amphibolites are medium-fine grained and are characterised mainly by hornblende and plagioclase with minor quartz while the metasediments are characterized by quartz, plagioclase, biotite, muscovite, microcline and epidote. The granites are made of quartz, biotite, plagioclase, microcline, chlorite, epidote, sericite and muscovite. The metamorphic rocks of Oke-Awun have been subjected to Amphibolite facies regional metamorphism which has been locally overprinted by greenschist facies retrogression.