Geochemical and Mineralogical Processes Controlling Gold Mineralization in the Ilesha-Ifewara Belt of Southwestern

Abstract

This study presents a novel integration of tectonic discrimination diagrams and mineralogical characterization to investigate the geochemical and mineralogical controls on gold mineralization in soils derived from the Precambrian Pan-African Basement Complex of the Ilesha–Ifewara Belt, southwestern Nigeria. Fieldwork involved systematic sampling of B- horizon lateritic profiles samples across Araromi (Ile-Ife), Ilesha, Iwara and Ifewara, areas historically recognized for auriferous quartz veins and structurally controlled mineralization. Major and trace element concentrations were determined using X-ray Fluorescence and Atomic Absorption Spectroscopy, while mineral phases were characterized by X-ray Diffraction and Scanning Electron Microscopy. Geochemical variation diagrams, including K₂O/Na₂O vs SiO₂ and Ba-Rb- Nb plots, reveal a consistent Oceanic Island Arc signature, indicating that the regolith inherits its chemistry from arc-related igneous protoliths emplaced during the Pan-African orogeny. The soils are silica (50 – 56 wt%) - and alumina (26-30 wt%) -rich, with marked depletion of CaO (>2 wt%), Na₂O (>0.5wt%) and K₂O (>1.0 wt%) and strong enrichment of immobile oxides (Al₂O₃ (< 25 wt%), TiO₂ (<1.0 wt%)), reflecting prolonged tropical lateritization. Gold occurs in association with cobalt, zinc, and nickel, while ternary diagrams highlight cobalt as a robust pathfinder, correlating with the highest gold values. The results demonstrate that integrating geochemical variation diagrams with mineralogical data effectively identifies the tectonic setting, alteration processes, and pathfinder elements of gold deposits. The findings provide a scientific framework for exploration in the Ife-Ilesha Schist Belt and similar West African terrains, underscoring the importance of lateritic geochemistry for targeting concealed orogenic gold mineralization.