Geochemical studies of the Gyeongchang W-Mo mine, Republic of Korea: progressive meteoric water inundation of a magmatic hydrothermal system

The Gyeongchang W-Mo mine is located within the Cretaceous Gyeongsang basin along the southeastern margin of the Korean peninsula. The ore mineral paragenesis can be divided into four distinct stages: W-Mo, Fe oxide, Pb-Zn, and carbonate. Fluid inclusion data indicate progressive decreases in temperature and salinity within each stage with increasing paragenetic time. These trends are interpreted to indicate progressive mixing of high-salinity, magmatic hydrothermal fluids with cooler, less acidic, more oxidizing meteoric waters. There is a systematic decrease in calculated δ¹⁸O_water values with decreasing temperature in the Gyeongchang hydrothermal system. The δD values of inclusion waters also decrease with paragenetic time. It is suggested that without significant introduction of meteoric waters into the Gyeongchang hydrothermal system, its deposits would be simple quartz-wolframite-molybdenite veins rather than a complex sequence of W-Mo, Fe oxide, Pb-Zn, and precious metal mineralization. -from Authors