Mineral chemistry, fluid inclusion and stable isotope studies of the Suyoc epithermal veins: Insights to Au-Cu mineralization in southern Mankayan Mineral District, Philippines

The Suyoc prospect is an epithermal vein-type mineralization located at the southern part of Mankayan Mineral District, Northern Luzon, Philippines. prospect’s veins are hosted in volcaniclastic rocks and conglomerate, which belong to Late Oligocene Early Miocene Balili Formation Middle Conglomerate, respectively. These classified into three major types: quartz vein, quartz-sulfide quartz-carbonate vein. vein exhibits massive cockade textures associated with pyrite + chalcopyrite. consists comb chalcopyrite sphalerite. has rhodochrosite sphalerite galena Au/Ag ± bournonite. In addition, gypsum occurs as a minor vein-type. Fluid inclusion measurements from vein-types revealed 230–250 °C formation temperatures 1.0–3.5 wt. % NaCl equivalent salinity, values consistent deposits. Quartz (e.g., massive, cockade, comb, crustiform) dominance liquid-rich fluid inclusions do not suggest that boiling primary mechanism deposition. Possible mechanisms inferred meteoric water dilution based on homogenization versus salinity trend presence wall rock interaction FeS crystals mole percent (0.51 8.30) indicate intermediate sulfidation state. alteration minerals illite, chlorite, near-neutral pH condition. δ34S values, vary −1.1 +3.9‰, reduced condition when compared representative bulk value for District. characteristics conditions strongly (ISE) style mineralization. Moreover, δDwater (−63 −66‰) δ18Owater (−3.9 −1.1‰) late stage magmatic-hydrothermal system similar other ISE deposits Luzon Segment Victoria, Acupan Antamok). Given these, underexplored District implies potential undiscovered cogenetic porphyry Cu high area.