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http://dx.doi.org/10.9719/EEG.2022.55.2.171

Au-Ag-bearing Ore Mineralization at the Geochang Hydrothermal Vein Deposit  

Hong, Seok Jin (Intellegio)
Lee, Sunjin (Department of Earth and Environmental Sciences, Chungbuk National University)
Choi, Sang-Hoon (Department of Earth and Environmental Sciences, Chungbuk National University)
Publication Information
Economic and Environmental Geology / v.55, no.2, 2022 , pp. 171-181 More about this Journal
Abstract
The Geochang Au-Ag deposit is located within the Yeongnam Massif. Within the area a number of hydrothermal quartz and calcite veins were formed by narrow open-space filling of parallel and subparallel fractures in the granitic gneiss and/or gneissic granite. Mineral paragenesis can be divided into two stages (stage I, ore-bearing quartz vein; stage II, barren calcite vein) by major tectonic fracturing. Stage I, at which the precipitation of major ore minerals occurred, is further divided into three substages (early, middle and late) with paragenetic time based on minor fractures and discernible mineral assemblages: early, marked by deposition of pyrite with minor pyrrhotite and arsenopyrite; middle, characterized by introduction of electrum and base-metal sulfides with minor sulfosalts; late, marked by hematite with base-metal sulfides. Fluid inclusion data show that stage I ore mineralization was deposited between initial high temperatures (≥380℃ ) and later lower temperatures (≤210℃ ) from H2O-CO2-NaCl fluids with salinities between 7.0 to 0.7 equiv. wt. % NaCl of Geochang hydrothermal system. The relationship between salinity and homogenization temperature indicates a complex history of boiling, fluid unmixing (CO2 effervescence), cooling and dilution via influx of cooler, more dilute meteoric waters over the temperature range ≥380℃ to ≤210℃. Changes in stage I vein mineralogy reflect decreasing temperature and fugacity of sulfur by evolution of the Geochang hydrothermal system with increasing paragenetic time. The Geochang deposit may represents a mesothermal gold-silver deposit.
Keywords
Geochang deposit; Au-Ag; vein deposit; $H_2O-CO_2$-NaCl; mesothermal;
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Times Cited By KSCI : 1  (Citation Analysis)
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