Temperature-chloride mixing diagrams at 500 and 1000 bars, up to 600°C and 60 NaCl wt.%, are constructed in order to understand the mixing behavior of saline and dilute hydrothermal solutions. On the basis of density data on NaCl solutions, these mixing diagrams are recast onto homogenization temperature-chloride mixing diagrams for the practical applications to the interpretations of fluid inclusion data.
Temperature-chloride mixing diagrams as well as homogenization temperature-chloride mixing diagrams indicate that the mixing of saline (<25 wt.%) hightemperature solution with dilute low-temperature solution shows near-linear relationship between temperature (or homogenization temperature) and chloride concentration. Larger decrease in temperature than that in concentration is found for the fluids with higher concentrations.
Homogenization temperature and salinity data for vein quartz from the Fujigatani and Kiwada tungsten deposits are shown to be the indication for the mixing of saline high-temperature (7 wt.% NaCl eq. and 360°C) solution with dilute low-temperature (2 wt.% NaCl eq. and 250°C) solution.

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