Origin and evolution of W-Mo-producing fluids in a granitic hydrothermal system: geochemical studies of quartz vein deposits around the Susan granite, Hwanggangri district, Republic of Korea

The Hwanggangri mineralized district is located approximately 130 km southeast of Seoul within the Paleozoic Ogcheon belt of South Korea. W-Mo-bearing quartz veins fill fractures in the granite and its host rocks which comprise early Paleozoic limestone-rich sedimentary rocks. The ore mineral paragenesis can be divided into three stages, based on the textural relationships of different mineral assemblages: I (W-Mo stage), II (base metal sulfides stages), and III (barren carbonate-fluorite stage). There is a systematic decrease in the measured and calculated isotopic compositions of hydrothermal waters with increasing paragenetic time and decreasing temperature. The trend reflects the progressive increase of meteoric water involvement in the mineralizing system. Increasing involvement of progressively large volumes of meteoric water resulted in successive deposition of base metal sulfides, fluorite, and carbonates. -from Authors