1986 Volume 36 Issue 200 Pages 555-572
Gold and silver bearing quartz veins of the Geumwang mine in South Korea occur in Cretaceous granite altered hydrothermally. Ores from the mine are exceptionally silver rich as the Korean type gold deposit. The ore minerals occur in two or three sulfide bands formed at early to middle stages and a sulfosalt band at the late stage of mineralization. Electrum and silver minerals of polybasite, pyrargyrite and argentian tetrahedrite appears in sulfide band or stringer consisting of pyrite, arsenopyrite, galena, sphalerite, chalcopyrite and quartz in the vein. Also silver-antimony sulfosalt minerals such as pyrargyrite, polybasite, miargyrite, diaphorite and argentian tetrahedrite with native silver occur as a band in central portion of the quartz vein in association with some amounts of pyrite, sphalerite, arsenopyrite and quartz. Composition of electrum is 48.4 to 52.7 wt% Ag (63.0 to 67.4 at% Ag). Meanwhile sphalerite has 2.2 to 4.2 mole% Fes. Homogenization temperatures of fluid inclusion (two phases) in quartz of the sulfide band are from 183°to 310°C(240°C in average) with a peak at 240°C, commonly 220°to 270°C. The ore mineralogy suggests that temperature (T) and sulfur fugacity (fs2) of the formation of the sulfide and sulfosalt bands are estimated as T: 190°to 240°C, fs 2: 10 -15.5 to 10 -13.5 atm, and T: 130°to 170°C, fs2: 10 -19.5 to 10 -17.0 atm, respectively. Such low temperature and low sulfur fugacity mineralization crystallized silver-antimony sulfosalts are considered.to be singular as the Korean type gold deposit.
