Analysis of the Structural Controls and Genesis of Quartz Vein-Hosted Gold Mineralisation in the Ilesha Gold Belt, Osun State

The Ilesha gold belt in Osun State, South West Nigeria, is one of Nigeria's most historically productive gold-bearing terrains, yet the structural controls and genetic model of gold mineralisation remain poorly understood compared to comparable West African gold districts. This study analyses the structural controls and investigates the genesis of quartz vein-hosted gold mineralisation in the Ilesha gold belt through integrated geological, geochemical, and fluid inclusion methods. Systematic structural mapping of veins, shear zones, and foliation was conducted at eight prospect areas, and kinematic analysis was performed using vein geometry, slickenside lineations, and displacement indicators. Gold and pathfinder element geochemistry of 98 vein and altered rock samples were determined. Fluid inclusion microthermometry was conducted on doubly polished wafers from representative quartz veins. Results indicate that gold mineralisation is controlled by NNE-trending, sinistral shear zones developed within metavolcanic sequences during progressive Neoproterozoic deformation. Fluid inclusion data reveal a low-salinity aqueous carbonic fluid with homogenisation temperatures of 250 to 320 degrees Celsius, consistent with an orogenic gold deposit model. Ore shoot development is controlled by shear zone dilation at structural jogs and intersections. The study proposes a refined geological model for the Ilesha belt that predicts down-plunge ore shoot continuity at several untested prospects and provides exploration targeting criteria. Keywords: gold mineralisation, Ilesha gold belt, structural controls, fluid inclusions, Osun State.