Mineralogical and Geochemical Composition of Charnockites in Ikere-Ekiti,southwestern Nigeria

Charnockite in Ikere-Ekiti area of southwestern Nigeria are a significant component of the Precambrian Basement Complex. The region is underlain by migmatite-gneiss-quartzite complex, granites and charnockite. This rock types display various structural features indicative of polycyclic deformation episodes resulting in various structures such as folds, joints, dykes and veins. This study focuses on the mineralogical and geochemical characteristics of charnockite in Ikere-Ekiti, it involves a combination of fieldwork, petrographic analysis, and geochemical investigations. Some occurrences show porphyritic textures due to large feldspar phenocrysts, color which is dark greenish-grey to black, attributed to mafic minerals such as pyroxene and Biotite. Weathering and alteration of charnockite in Ikere-Ekiti exhibit development of spheroidal exfoliation and boulder formations. Petrographic study reveals the charnockite is predominantly composed of quartz ( 28 − 31%; ca. 29.2% ), microcline ( 18 − 22%; ca. 19.8% ), plagioclase ( 30 − 33%; ca. 31.6% ), muscovite ( 4 − 6%; ca. 5% ), hornblende ( 3 − 5%; ca. 4% ), and Biotite ( 8 − 13%; ca. 10.4% ). Geochemical studies suggest a composition of major elements and trace elements. The major elements are SiO2(68.12 − 71.14%; ca. 69.43% ), Al2O3(12.84 − 14.08%; ca. 13.62% ), Fe2O3(3.77 − 4.40%; ca. 4.13% ), CaO(0.81 − 1.81%; ca. 1.35% ), K2O(4.12 − 4.44%; ca. 4.26% ), Na2O(3.02 − 3.98% ca. 3.46% ). The granular texture of the charnockite is characterized by coarse-grained and interlocking minerals. The petrology of charnockite suggests they are formed through partial melting of dry mafic lower crustal rocks under granulite facies conditions. Keywords: Ikere-Ekiti, charnockite, granulite facies, partial melting, polycyclic deformation