Mineral Paragenesis and Fluid Inclusion Study of Ssangjeon Tungsten Deposits

쌍전중석광상(雙田重石鑛床)의 광물공생(鑛物共生)과 유체포유물연구(流體包有物硏究)

Ssangjeon tungsten ore deposits is a complex pegmatite deposits embedded along the contact between pre-Cambrian Buncheon granite gneiss and amphibolite. This pegmatite vein developed 2 km along the strike and thickness varies from 10m to 40m. Mineral constituent of the normal pegmatite are quartz, microcline, plagioclase, muscovite, biotite, tourmaline and garnet. The vein paragenesis is complicated by repeated deposition of quartz but three distinct depositional stage can be recognized. Quartz A stage is the stage of the earliest milky white quartz deposition as a rock forming mineral of normal pegmatite. Quartz B stage is the stage of gray to dark gray quartz replace earlier formed normal pegmatite minerals. Quartz C stage is the stage of latest white translucent massive quartz replace quartz A and B. Tungsten ore minerals and other sulfide minerals were precipitated during quartz B stage. Ore minerals are ferberite and scheelite. Minor amount of molybdenite, arsenopyrite, pyrrhotite, pyrite, chalcopyrite, sphalerite, galena, pentlandite, bismuthinite, native bismuth and marcasite accompanied. Fluid inclusion in quartz A and B are gaseous inclusions and liquid inclusions are contained in quartz C as a primary inclusions. Salinity of inclusions in quartz A and B ranges from 4.5 to 9.5 wt. % and from 5.1 to 6.0 wt. % equivalent NaCl respectively. Homogenization temperature of quartz A; quartz B and quartz C ranges from 415 to $465^{\circ}C$, from 397 to $441^{\circ}C$ and from 278 to $357^{\circ}C$. $CO_2$ content of the ore fluid increased at the ends of quartz B stage.