Geology and Geochemical Evidence for Structurally Controlled Hydrothermal Metallic Mineralization in the Western Oban Massif, Southeastern Nigeria

Abstract

The Precambrian Basement Complex of southeastern Nigeria forms part of the Nigerian Basement Complex and exhibits geological characteristics comparable to Archean-Proterozoic terranes known for deformation-driven hydrothermal systems. This study investigates the geology, structural framework, and whole-rock geochemistry of basement rocks in the western Oban Massif to evaluate evidence for structurally controlled hydrothermal metal redistribution. Field mapping identifies metasedimentary, meta-igneous, and intrusive lithologies, including phyllites, schists, amphibolites, pegmatites, and quartz-feldspathic veins, commonly associated with linear and planar structures trending N–S, NE-SW, and NW-SE that acted as pathways for hydrothermal fluid circulation and localized metal redistribution. Whole-rock geochemical data show elevated SiO₂, Al₂O₃, and total Fe₂O₃ and low MnO, MgO, CaO, Na₂O, TiO₂, and P₂O₅, consistent with silica enrichment and fluid-rock interaction. Trace-element distributions display lithology-dependent enrichment patterns, with phyllites enriched in Pb, Ba, Cr, Rb, Zr, Y, and Zn; schists in Rb, Ba, Sr, Cr, Zr, and Ni; amphibolites in Ba, Sr, Rb, Y, Zr, and Zn; quartz-feldspathic veins in Zn, Sr, Cr, Pb, and Ba; and pegmatites in Rb, Sr, Ba, Cr, Zn, and Zr. Enrichment factor calculations and diagnostic geochemical ratios indicate background to moderate enrichment in host rocks and localized moderate to strong enrichment within structurally controlled veins and pegmatites. Collectively, the geological, structural, and geochemical evidence indicates that the western Oban Massif records deformation-controlled hydrothermal metal redistribution comparable to systems documented in Nigerian schist belts and other Precambrian basement terranes worldwide. Although economic mineralization is not established, the results highlight geochemical permissiveness for localized metal concentration and identify the western Oban Massif as an underexplored metallogenic system in southeastern Nigeria.