Major Oxide and Trace Element Geochemistry of Basement Rocks in the Ikole–Itapaji Area, Southwestern Nigeria: Implications for Metallic Mineralization Potential

Abstract

This study investigated the geology, petrogenesis, and mineralization potential of the crystalline rocks in the Ikole–Itapaji–Ake-Ako area, southwestern Nigeria, by integrating geological mapping with whole-rock major- and trace-element geochemistry. Detailed field mapping identified the dominant lithological units as migmatite, granite gneiss, granite, charnockite, and pegmatite, with well-developed structural features including foliations, joints, fractures, and quartz veins that provide favourable pathways for hydrothermal fluid circulation. Thirty-five fresh rock samples were collected during field investigations, from which twenty representative samples were selected for whole-rock geochemical analysis based on lithological representation, freshness, mineralogical diversity, textural and structural characteristics, and spatial distribution. Major-element analyses were carried out using Inductively Coupled Plasma–Mass Spectrometry (ICP–MS) following partial multi-acid digestion with hydrochloric acid (HCl), nitric acid (HNO₃), and perchloric acid (HClO₄), combined with lithium metaborate fusion to ensure complete dissolution of refractory silicate minerals and accurate determination of the major rock-forming elements. Major-oxide geochemistry was evaluated using Harker variation diagrams, the A/CNK–A/NK alumina saturation diagram, and the Fe-number discrimination diagram, while trace-element data were interpreted using factor analysis and correlation coefficient analysis. The Harker variation diagrams indicate that the studied rocks evolved predominantly through fractional crystallization, characterized by progressive depletion of MgO, FeOt, CaO, and TiO₂ with increasing SiO₂. The alumina saturation diagram shows that the rocks range from metaluminous to weakly peraluminous compositions, whereas the Fe-number discrimination diagram indicates predominantly magnesian affinities with minor transitional ferroan characteristics. Factor analysis identified Cu–Ni–Co–Fe–Zn as the principal mineralization association, explaining most of the geochemical variability, while As–Th–Ag–Pb constitute a secondary association related to lithological variation and hydrothermal alteration. Correlation coefficient analysis further revealed strong positive relationships among Cu, Ni, Co, Fe, and Zn, indicating a common geochemical source and structurally controlled magmatic–hydrothermal mineralization. The integrated geological and geochemical results demonstrate that the Ikole–Itapaji–Ake-Ako area possesses favourable conditions for sulphide mineralization and provide a valuable framework for future mineral exploration within the Precambrian Basement Complex of southwestern Nigeria.