Abstract
Cadmium contents of sphalerites are invariably higher than 0.9 wt% from both the vein-type and skarn-type major tungsten deposits at Kaneuchi, Ohtani, Takatori, Fujigatani, Kiwada, and Kuga mines. The contents are high compared with those of most natural sphalerites. Sphalerites from the quartz veins that intersect the skarns of the Fujigatani and Kiwada deposits are higher in cadmium contents than those from the skarns of the same deposits. Considering that tungsten mineralization in the Fujigatani and Kiwada deposits is closely related to the formation of quartz veins, it is likely that high cadmium contents of sphalerites have an intimate genetical relationship with tungsten mineralization in these deposits. Sphalerite from the quartz veins of the Suho ore body of the Kuga deposit is higher in cadmium content than that from the quartz veins of the Ideno-oku ore body of the same deposit. As the ore grade of tungsten in the Suho ore body seems to be higher than that in the Ideno-oku ore body, the higher cadmium content of sphalerite from the Suho ore body also supports the close relationship between cadmium content of sphalerite and tungsten mineralization.
Fluid inclusion data for the Kiwada and Kuga deposits suggest that the temperatures of the hydrothermal solutions do not significantly affect the cadmium contents of sphalerites from these deposits. It is suggested that high activity ratios of Cd2+/Zn2+ in the hydrothermal solutions are important as the cause of the enrichment of cadmium in sphalerite, and that these are characteristic for major tungsten deposits in Japan.
