Enrichment of copper in ore-forming fluid of copper-tungsten mineralization of the yamaguchi skarn deposit, iwate, Japan

摘要

Chemical composition of the fluids in the fluid inclusions of quartz from the pegmatite veins of the Yamaguchi W-Cu skarn deposit was measured by a combination of the crush-leach method in deionized water and chemical analysis using PIXE. Chemical composition of the fluids is characterized by a low molar ratio of Na/K and a high Cu concentration. The molar ratio of Cu/(Cu+Fe+Zn) of the fluid inclusions is higher than that of massive sulfide deposits on the seafloor. The molar ratio of Cu/(Cu+Fe+Zn) of the fluid inclusions is similar to the ratios of the vapor rich fluid inclusions from the quartz cassiterite veins hosted within the Mole Granite in New South Wales, Australia. The high Cu concentration in fluid inclusions of quartz associated with the pegmatite veins from the Yamaguchi deposit suggests that the fluid emanating from the Miyako granitic melt at the later stage of crystallization had a high Cu content.