Analytical Study of Sulphide Mineralisation in the Basement Complex of Nasarawa State

Sulphide mineral occurrences hosted within the Precambrian basement complex of Nasarawa State, North Central Nigeria, have been identified in reconnaissance surveys but lack systematic analytical characterisation that would enable assessment of their economic significance and geochemical environmental implications. This study investigates the mineralogy, geochemistry, and genetic model of sulphide mineralisation in identified basement hosted occurrences across three localities in Nasarawa State. Ore samples and surrounding host rock specimens were collected from surface outcrops and shallow artisanal workings. Reflected light microscopy was used to characterise ore mineral assemblages, identifying pyrite, chalcopyrite, sphalerite, galena, and arsenopyrite as the dominant sulphide species, with accessory gold noted in several polished sections. Microprobe analysis provided quantitative compositions of individual sulphide phases to assess trace element substitutions. Whole rock geochemical analyses by inductively coupled plasma mass spectrometry were conducted on ore and associated altered wall rock samples to characterise metal zoning and enrichment factors. Sulphur isotope compositions were determined on separated sulphide mineral fractions to constrain fluid source and temperature of mineralisation. The study evaluates whether observed mineralisation characteristics are consistent with an orogenic gold model, volcanogenic massive sulphide model, or intrusion-related setting. The genetic interpretation guides target generation recommendations for systematic exploration drilling. Keywords: sulphide mineralisation, basement complex, ore microscopy, Nasarawa State, sulphur isotopes.