SYNCHROTRON RADIATION X-RAY FLUORESCENT ANALYSIS FOR FLUID INCLUSIONS IN QUARTZ FROM HYDROTHERMAL W-SN VEINS AT TAKATORI, CENTRAL JAPAN

The chemical analysis of fluid inclusions trapped in the crystal from the ores provides the nature of the ore-forming fluid. In this study, Synchrotron radiation X-ray fluorescence (SXRF) analysis has been successfully applied to determine the chemical composition of individual fluid inclusions. Beam line BL-4A at the High Energy Accelerator Research Organization (KEK), Tsukuba, Japan was used for the analysis.  The analytical methods are almost the same as those in Nagaseki et al. (2006).

 Samples we used are quartz from the hypothermal wolframite-bearing quartz veins at the Takatori mine. The pragenetic sequence of the vein is characterized by the early wolframite-topaz-fluorite, middle sulfide-rich, and late cassiterite-carbonate stages.

Quartz appears as dominant mineral in all stages. Quartz of the middle stage grew in druse as large (up to 10 cm) euhedral crystals. Fluid inclusions hosted in quartz of middle stage are carefully examined and their temporal relation was obtained from crosscutting relationship.

In the qualitative analysis for the inclusions in quartz, heavy metals such as, Mn, Fe, Zn, Cu and As were recognized, however, W was not detected. Concentration of these metals are; Mn, 450-100 ppm, Fe, 900-300 ppm, Zn, 230-100 ppm, and Cu, 180-100 ppm,and their concentrations decreases systematically toward later stage. The evolution of the ore-forming fluid and the formation of the Takatori W deposits will be modeled and discussed.