• Economic and Environmental Geology
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• v.46 no.2
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• pp.199-206
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• 2013

The Daehyun gold-silver deposit consists of two hydrothermal quartz veins that fill NE-trending fractures in the Cambro-Ordovician calcitic marble. I have sampled wallrock, hydrothermaly-altered rock and gold-silver ore vein to study the element dispersion and element gain/loss during wallrock alteration. The hydrothermal alteration doesn't remarkably recognized at this deposit and consists of mainly calcite, dolomite, quartz and minor epidote. The ore minerals composed of arsenopyrite, pyrrhotite, pyrite, sphalerite, stannite, chalcopyrite, galena, electrum, native bismuth and silver-bearing mineral. Based on analyzed data, the chemical composition of wallrock consists of mainly $SiO_2$, CaO, $CO_2$ with amounts of $Al_2O_3$, $Fe_2O_3(T)$ and MgO. The contents of $SiO_2$, $Fe_2O_3(T)$, MgO, CaO and $CO_2$ vary significantly with distance from ore vein. The element dispersion doesn't remarkably recognized during wallrock alteration and only occurs near the ore vein margin because of physical and chemical properties of wallrock. Remarkable gain elements during wallrock alteration are $Fe_2O_3(T)$, total S, Ag, As, Bi, Cd, Cu, Ni, Pb, Sb, Sn, W and Zn. Remarkable loss elements are $SiO_2$, MnO, MgO, CaO. $CO_2$ and Sr. Therefore, Our result may be used when geochemical exploration carry out at deposits hosted calcitic marble in the Hwanggangri metallogenic district.

• Economic and Environmental Geology
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• v.53 no.3
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• pp.221-234
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• 2020

We occur together with telluride minerals. Fluid inclusions in the euhedral quartz crystals are mainly aqueous liquid-rich inclusions, which have salinities about 0.18-2.24 wt% NaCl equivalent. Some quartz vein contains aqueous vapor-rich inclusions as well. Homogenization temperatures of the assemblages of the liquid-rich inclusions are about 141-384 ℃, and the temperatures are lower at the shallower vein samples. In the high Au-Ag grade depth intervals, relatively deeper fluids have relatively higher salinities and homogenization temperatures, while shallower fluids show somewhat wider ranges. These might indicate that the deep Au-Ag bearing hydrothermal fluids at the Moisan area experienced phase separation as well as mixing with meteoric water by decreasing pressure. Au-Ag precipitation in the Moisan deposit is not associated with pyrite, but pyrite include Au-Ag bearing phase as an inclusion, which might possibly be tellurides or electrum. Au/Ag ratios in the Au-Ag bearing phase do not change with different depth.

• Proceedings of the KSEEG Conference
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• 2002.10a
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• pp.119-136
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• 2002

Contrasts in the style of the gold-silver mineralization in geologic and tectonic settings in Korea, together with radiometric age data, reflect the genetically different nature of hydrothermal activities, coinciding with the emplacement age and depth of Mesozoic magmatic activities. It represents a clear distinction between the plutonic settings of the Jurassic Daebo orogeny and the subvolcanic environments of the Cretaceous Bulgugsa igneous activities. Dunng the Daebo igneous activities (c.a. 200～150 (\ulcorner) Ma) coincident with orogenic time, gold mineralization took place between c.a. 195 and 135 (127 \ulcorner) Ma. The Jurassic Au deposits commonly show several characteristics; prominent association with pegmatites, low Ag/Au ratios In the ore-concentrating parts, massive vein morphology and a distinctively simple mineralogy including Fe-rich sphalerite, galena, chalcopyrite, arsenopyrite, Au-rich electrum, pyrrhotite and/or pyrite. During the Bulgugsa igneous activities (110～50 Ma), the precious-metal deposits are generally characterized by such features as complex vein morphology, medium to high Ag/Au ratios in the ore concentrates, and diversity of ore minerals including base-metal sulfides, pyrite, arsenopyrite, Ag-rich eletrum and native silver with Ag sulfides, Ag-Sb-As sulfosalts and he tellurides. Vein morphology, mineralogical, fluid inclusion and stable isotope results indicate the diverse genetic natures of hydrothermal systems in Korea. The Jurassic Au-dominant deposits (orogenic type) were formed at the relatively high temperature (about 300$^{\circ}$ to 45$0^{\circ}C$) and deep-crustal level (4.0$\pm$1.5 kb) from the hydrothermal fluids containing more amounts of magmatic waters ($\delta$$^{18}$ $O_{H2O}$; 5～10$\textperthousand$). It can be explained by the dominant ore-depositing mechanisms as $CO_2$ boiling and sulfidation, suggestive of hypo- to mesothermal environments. In contrast, the Cretaceous Au-dominant (l13～68 Ma), Au-Ag (108～47 Ma) and AE-dominant (103～45 Ma) deposits, which correspond to volcanic-plutonic-related type, occurred at relatively low temperature (about 200$^{\circ}$ to 35$0^{\circ}C$) and shallow-crustal level (1.0$\pm$0.5 kb) from the ore-forming fluids containing more amounts of less-evolved meteonc waters ($\delta$$^{18}$ $O_{H2O}$;-10～5$\textperthousand$). These characteristics of the Cretaceous precious-metal deposits can be attributed to the complekities in the ore-precipitating mechanisms (mixing, boiling, cooling), suggestive of epi- to mesothermal environments. Therefore, the differences of the emplacement depth between the Daebo and the Bulgugsa igneous activities directly influence the unique temporal and spatial association of the deposit styles.les.

• Economic and Environmental Geology
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• v.31 no.2
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• pp.89-99
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• 1998

The gold-silver mineralizations in Korea are closely related to Jurassic Daebo igneous activity (121 and 183 Ma) and Cretaceous Bulgugsa igneous activity (60 and 110 Ma). A compilation and re-evaluation of chemical data in arsenopyrite suggest that the As contents vary, reflecting different genetic environments or mineral assemblages. The gold-silver vein deposits from various mineralized area were investigated using arsenopyrite geothermometer. Arsenopyrites from the Jurassic Au-dominant deposits are distinct by high As contents (29.68~33.46 atomic %) with narrow variations, equivalent to a temperature range of $370{\sim}450^{\circ}C$ and a sulfur fugacity of about $10^{18}-10^{-6}$ atm. On the contrary, arsenopyrites from the Cretaceous Au-Ag and Ag-dominant deposits show a wider range in atomic % As composition of 27.47-32.74. They may have formed at temperatures of $250{\sim}350^{\circ}C$ and about $f_{S_2}=10^{-12}-10^{-10}$ atm. The data of arsenopyrite geothermometer, electrum-sphalerite geothermometer, fluid inclusions, vein morphology and emplacement depth of igneous rocks indicate that the gold mineralizations of Group IIA occurred at temperatures between 300 and $500^{\circ}C$ at depth of several tens km or more (about 4-5 kbar), and the gold-silver deposits of Groups III, IV and V were formed at a temperature range of about $170{\sim}370^{\circ}C$ under the shallow environment (<1 kbar).

• Economic and Environmental Geology
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• v.29 no.6
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• pp.677-687
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• 1996

The Buckchang deposits which is located in the Ockcheon metamorphic zone, are emplaced along $N20-30^{\circ}E$ trending fissure sets. So it is a sort of fissure-filling ore deposits. The results of mineral paragenetic studies suggest two stages of hydrothermal mineralization; stage I: base-metal sulfides stage, stage II: late base-metal sulfides, electrum and silver-bearing sulfosalts stage. The silver-bearing sulfosalts occured as the Buckchang mine are mainly argentite and, minor of canfieldite, tetrahedrite, etc. Au:Ag ratios of the electrums show a highly limited range of nearly 1:1 in atomic %. The temperature, salinity and pressure of the Buckchang deposits estimated from fluid inclusion and sulfur isotope studies are as follows; stage I: $174{\sim}250^{\circ}C$, 0.35~4.01 NaCl eq. wt.%, 0.40~1.00 Kbar, stage II: $138{\sim}222^{\circ}C$, 1.9~8.4 NaCl eq. wt.%, 0.22~0.53 Kbar. The estimated oxygen and sulfur fugacity during stage I mineralization, based on phase relation of associated minerals, range from $10^{-39.7}{\sim}10^{-44.7}$ atm. and $10^{-13.4}{\sim}10^{-18.1}$ atm., respectively. All these evidences suggest that the Buckchang deposits are polymetallic epithermal ore deposits.

• Economic and Environmental Geology
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• v.25 no.2
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• pp.115-131
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• 1992

Late Cretaceous (90.5 Ma), epithermal gold-silver vein mineralization of the Weolseong and Samchang mines in the Sulcheon area, 60 km southeast of Taejeon, can be separated into two distinct stages (I and II) during which fault-related fissures in Precambrian gneiss and Cretaceous (102 Ma) porphyritic granite were filled. Fluid inclusion and mineralogical data suggest that quartz-sulfide-electrum-argentite-forming stage I evolved from initial high temperatures $({\approx}340^{\circ}C})$ to later lower temperatures $({\approx}140^{\circ}C})$ at shallow depths of about 400 to 700 m. Ore fluid salinities were in the range between 0.2 and 6.6 wt. % eq. NaCl. A simple statistic model for fluid-fluid mixing indicates that the mixing ratio (the volumetric ratio between deep hydrothermal fluids and meteoric water) systematically decreased with time. Gold-silver deposition occurred at temperatures of $230{\pm}40^{\circ}C$ mainly as a result of progressive cooling of ore-forming fluids through mixing with less-evolved meteoric waters. Measured and calculated hydrogen and oxygen isotope values of hydrothermal fluids indicate meteoric water dominance, approaching unexchanged meteoric water values. The geologic, mineralogic, and geochemical data from the Weolseong and Samchang mines are similar to those from other Korean epithermal gold-silver vein deposits.

• Economic and Environmental Geology
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• v.32 no.6
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• pp.561-573
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• 1999

Mesothermal gold deposits of the Heungdeok, Daewon and Ilsaeng mines in the Youngdong area occur in fault shear zones in Precambrian metamorphic rocks of central Sobaegsan Massif, Korea, and formed in single stage of massive quartz veins (0.3 to 3 m thick). Ore mineralogy is simple, consisting dominantly of pyrrhotite, sphalerite and galena with subordinate pyrite, chalcopyrite, electrum, tetrahedrite and native bismuth. Fluid inclusion data indicate that hydrothermal mineralization occurred at high temperatures (>240$^{\circ}$ to 400$^{\circ}$C) from $H_{2}O-CO_{2}(-CH_{4})$-NaCI fluids with salinities less than 12 wt. % equiv. NaC!. Fluid inclusions in vein quartz comprise two main types. These are, in decreasing order of abundance, type I (aqueous liquid-rich) and type II (carbonic). Volumetric proportion of the carbonic phase in type II inclusions varies widely in a single quartz grain. Estimated $CH_4$ contents in the carbonic phase of type II inclusions are 2 to 20 mole %. Relationship between homogenization temperature and salinity of fluid inclusions suggests a complex history of fluid evolution, comprising the early fluid's unmixing accompanying $CO_2$ effervescence and later cooling. Estimated pressures of vein filling are at least 2 kbars. The ore mineralization formed from a magmatic fluid with the ${\delta}^{34}S_{{\Sigma}S}$, ${\delta}^{18}O_{water}$ and ${\delta}D_{water}$ values of -2.1 to 2.2$\textperthousand$, 4.7 to 9.3$\textperthousand$ and -63 to -79$\textperthousand$, respectively. This study validates the application of a magmatic model for the genesis of mesothermal gold deposits in Youngdong area.

• Economic and Environmental Geology
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• v.22 no.1
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• pp.1-16
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• 1989

Electrum-galena-sphalerite mineralization of the Yangpyeong-Weonju Au-Ag area was deposited in three stages of quartz and calcite veins which fill fault breccia zones. Fluid inclusion and stable isotope data show that ore mineralization was deposited at temperatures between $260^{\circ}C$ and $180^{\circ}C$ from fluids with salinities between 8.9 and 2.9 equivalent weight percent NaCl. Evidence of boiling indicates pressures of <50 bars, corresponding to depths of 220 to 550 m, respectively, assuming lithostatic and hydrostatic loads. Au-Ag deposition was likely a result of bolling coupled with cooling. Within stages I and II there is an apparent increase in ${\delta}^{34}S$ values of $H_2S$ with paragenetic time ; early -1.4~2.7‰ to later 6.6-9.2‰. The progressively heavier $H_2S$ values can be generated through isotopic re-equilibration in the ore fluid following removal of $H_2S$ by boiling or precipitation of sulfides. Measured and calculated hydrogen and oxygen isotope values of ore-forming fluids suggest meteoric water dominance, approaching unexchanged meteoric water values. Comparison of these values with those of other Korean Au-Ag deposits reveals a relationship between depth and degree of water-rock interaction. All investigated Korean Jurassic and Cretaceous gold-silver-bearing deposits have fluids which are dominantly evolved, meteoric water, but on1y deeper systems (${\geq}1.25km$) are exclusively gold-rich.

• Journal of the Mineralogical Society of Korea
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• v.32 no.2
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• pp.87-102
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• 2019

Pallancata Ag mine is located at the Ayacucho region 520 km southeast of Lima. The geology of mine area consists of mainly Cenozoic volcanic-intrusive rocks, which are composed of tuff, andesitic lava, andesitic tuff, pyroclastic flow, volcano clasts, rhyolite and quartz monzonite. This mine have about 100 quartz veins in tuff filling regional faults orienting NW, NE and EW directions. The Ag grades in quartz veins are from 40 to 1,000 g/t. Quartz veins vary from 0.1 m to 25 m in thickness and extend to about 3,000 m in strike length. Quartz veins show following textures including zonation, cavity, massive, breccia, crustiform, colloform and comb textures. Wallrock alteration features including silicification, sericitization, pyritization, chloritization and argillitization are obvious. The quartz veins contain calcite, chalcedony, adularia, fluorite, rutile, zircon, apatite, Fe oxide, REE mineral, Cr oxide, Al-Si-O mineral, pyrite, sphalerite, chalcopyrite, galena, electrum, proustite-pyrargyrite, pearceite-polybasite and acanthite. The temperature and sulfur fugacity ($f_{s2}$) of the Ag mineralization estimated from the mineral assemblages and mineral compositions are ranging from 118 to $222^{\circ}C$ and from $10^{-20.8}$ to $10^{-13.2}atm$, respectively. The relatively low temperature and sulfur-oxygen fugacities in the hydrothermal fluids during the Ag mineralization in Pallancata might be due to cooling and/or boiling of Ag-bearing fluids by mixing of meteoric water in the relatively shallow hydrothermal environment. The hydrothermal condition may be corresponding to an intermediate sulfidation epithermal mineralization.

• Economic and Environmental Geology
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• v.55 no.2
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• pp.171-181
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• 2022

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.