Geochemical consideration of some granitoids around Ojirami-Ogbo and environs, southwestern Nigeria

Abstract

Five (5) granitoid samples from Ojirami-Ogbo and Environs in Akoko-Edo area of southwestern Nigeria were obtained with the aim of determining their geochemical properties using the XRF and Xrd techniques. Results from the analysis revealed the presence of SiO₂ (51.41-64.84%), Al₂O₃ (21.37-36.25%), Fe₂O₃ (5.89-8.02%), MgO (0.98-2.11%), K₂O (0.02-0.97%) and Na₂O (0.04-0.08%) all in wt%. Using the Al₂O₃ and SiO₂ saturation schemes in classifying igneous rocks, sample two, three, four and five gave Al2O3 wt% values of 33.30%, 32.00%, 23.20%, 21.37% greater than the molars proportions of (Al₂O₃/CaO+Na₂O+K₂O) with values 22.54, 30.06, 22.10 and 14.07, and are peraluminous rocks while sample one had 36.25% and 43.10, respectively and is considered to be metaluminous. The SiO₂ composition of the rocks ranges from 51.41-66.40% hence reveals a mafic to intermediate composition. The main felsic minerals from XrD analysis revealed the presence of quartz, alkali and plagioclase feldspars. Using the QAP diagram, the rocks fall within the granitoidal class.

Keywords: geochemical, silica-saturation, alumina-saturation, major oxides