Unconformity-related fluorite-baryte-base metal mineralization in the Benue Trough, Nigeria: A multifluid origin triggered by the separation of Pangaea

Unconformity-related hydrothermal vein-type deposits are key sources of high-purity fluorite, baryte, and base metals, with occurrences in Nigeria, particularly along the Benue Trough. However, the genesis of the Nigerian deposits is not well understood. This study examines fluid inclusion systematics from mineralized veins at Enyigba, Ameta, Ikwo, Otim Land, and Uburu-Abakaliki, using microthermometry, crush-leach analysis, and Raman spectroscopy. Fluid inclusion microthermometry reveals homogenization temperatures between 99 and 190 °C and salinities of 18.3–22 wt%NaCl + CaCl 2 , typical of unconformity-related hydrothermal vein systems. Geochemical data indicate the mineralizing fluids resulted from mixing of bittern brines (low Cl/Br), halite-dissolution brines (high Cl/Br), and oilfield brines, as shown by Cl/Br ratios and Rb/Cs values. Microraman spectroscopy suggests the presence of hydrocarbons, supporting the involvement of reduced oilfield brines. These findings point to a complex fluid mixing process, likely driven by crustal-scale faulting during the rifting of the Benue Trough in the context of Pangaea break-up. This research suggests a common ore-forming process for the Nigerian deposits. • First holistic fluid data set of Nigerian fluorite-baryte deposits. • Raman, microthermometry, crush leach and MicroXRF data. • Development of a holistic deposit model. • Genetic linkage to Pangea breakup. • Provenance of ore fluids.