• Economic and Environmental Geology
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• v.48 no.1
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• pp.1-13
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• 2015

The geology of the Seungryung Zn deposit, located in the Muzu basin, consists of Precambrian leucocratic granitic gneiss, Cretaceous clastic rocks, pyroclastic rocks, and intrusive rocks. The deposit shows a weakly skarnized hydrothermal replacement ore developed along limestone bed in the gneiss. The mineralization can be divided into three stages: the early skarnization producing garnet and pyroxene, the main mineralization in the middle stage precipitating most metallic minerals such as magnetite, sphalerite, chalcopyrite, pyrrhotite, Pb-Ag-Bi-S system minerals, and the late stage for altered or low temperature minerals such as chlorite and marcasite. Pb-Ag-Bi-S system minerals include heyrovskite-eskimoite solid solution, lillianite-gustavite solid solution, and vikingite. Chalcopyrite diseases are quite common in sphalerite showing bead chains and dusting textures. The ${\delta}^{34}S$ values of sulfides minerals are concentrated within the narrow range of 3.4~4.1‰ for pyrite, 3.3~4.3‰ for sphalerite, 4.0~4.3‰ for chalcopyrite, and 2.8‰ for galena, suggesting that most sulfur is of igneous origin. Sulfur isotope geothermometry is calculated to be $346{\sim}431^{\circ}C$, implying that the mineralization occurred at relatively high temperature. FeS contents of sphalerite are relatively high in the range of 6.58~20.16 mole% (avg. 16.58 mole%) with the enrichment of Mn compared to Cd, similarly to representative skarn Pb-Zn deposits in South Korea. On the contrary, sphalerite from Au-Ag deposits in the Seolcheon mineralized zone around the Seungryung deposit is enriched in Cd, showing similar feature like representative epithermal Au-Ag deposits. This suggests that around the related igneous rocks, magnetite and sphalerite were produced at high temperature in the Seungryung deposit, and with decreasing temperature and compositional change of mineralizing fluids, Au-Ag mineralization proceeded in the Seolcheon mineralized zone.