• Economic and Environmental Geology
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• v.55 no.2
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• pp.183-195
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• 2022

Hydrothermal gold deposits are evidence of intensive fluid flow through fault zones, and the resultant vein structures and textures reflect the fluid redistribution mechanism. This review introduces the suction pump and fault valve models as fluid circulation mechanisms causing hydrothermal gold deposits in the frameworks of the concepts of fault mechanics. The suction pump and fault valve models describe faulting-driven heterogeneous fluid flow and related vein formation mechanisms, accompanied by the cycles of (1) stress accumulation and fluid pressure build-up and (2) seismic rupture and stress/fluid pressure release. The models are available under different geological environments (stress conditions), and the vein structures and textures representing the mechanisms have similarities and differences. The suction pump and fault valve models must help better to interpret the origins of hydrothermal gold deposits in Korea and improve the efficiency of further exploration.

• Korean Journal of Food Science and Technology
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• v.35 no.2
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• pp.188-194
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• 2003

천마식품가공시 기초자료로 활용될 수 있는 천마 추출농축액의 리올로지 특성을 조사하였다. 천마의 열수 및 50% 에탄올 추출물운 각각 5, 10, 15, 및 20 Brix와 10, 20, 30, 40 및 50 Brix로 농축하여 제조하였다. 열수 및 50% 에탄올 농축액의 정상유동특성과 동적점탄성을 조사하였다. Power law model로 구한 n에 의하면 모든 열수 농축액들은 전형적인 의가소성$(n=0.484{\sim}0.802)$유체의 흐름특성을 보였고, 50% 에탄올 농축액들은 뉴튼유체$(n=0.875{\sim}1.078)$에 가까운 흐름특성을 나타내었다. 열수 및 50% 에탄올 농축액의 ${\eta}_{app}$는 온도가 증가함에 따라 감소하는 경향을 나타내었다. Herschel-Bulkley model에 의한 열수 및 50% 에탄올 농축액의 C는 각각 $0.030{\sim}1.255$ Pa와 $0.007{\sim}0.065$ Pa이었다. ${\eta}_{app}$에 대한 온도 및 농도의 영향은 arrhenius식으로 해석하였다. 열수 및 50% 에탄올 농축액의 $E_a$는 농도가 증가함에 따라 각각 $3.340{\sim}4.620{\times}10^3\;J/mol{\cdot}kg$과 $1.6289{\sim}18.6699{\times}10^3\;J/mol{\cdot}kg$의 범위로 나타났다. 진동수(angular frequency, ${\omega}$)가 증가할수록 저장탄성률(storage modulus, G#)과 손실탄성률(loss modulus, G@)은 일반적으로 증가하는 경향을 나타냈다. 50% 에탄올 농축액의 경우 모든 진동수에서 G#이 G@보다 높게 나타나 전형적인 저분자용액의 흐름특성을 보였다. 그러나 열수농축액의 경우 G@이 G#보다 높았고 0.5 rad/sec에서 교차점을 형성하였으며 전형적인 고분자 용액의 흐름특성을 나타내었다.

• Korean Journal of Food Science and Technology
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• v.24 no.6
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• pp.597-602
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• 1992

To improve utilization of boxthorn (Lycii Fructus), the boxthron and mixed boxthron (Lycii Fructus, Schizandrae Fructus, Corni Fructus, Zizyphi Fructus, Zingiberis Rhizoma, Cinnamami Cortex) hot-water extractable concentrates were prepared by vaccum evaporation and its rheological properties were investigated. The rheological properties of concentrates $(20{\sim}50^{\circ}Bx)$ followed power low model and showed a pseudoplastic behavior at the temperature range of $20{\sim}60^{\circ}C$. The apparent viscosity of $20^{\circ}Bx$, $30^{\circ}Bx$, $40^{\circ}Bx$ and $50^{\circ}Bx$ boxthron hot-water extractable concentrate was 0.0074 Pa s, 0.0175 Pa s, 0.0431 Pa s and 0.0988 Pa s, that of mixed boxthorn hot-water extractable concentrate was 0.0099 Pa s, 0.0328 Pa s, 0.0720 Pa s and 0.1940 Pa s at $20^{\circ}C$ and 1500 l/s, respectively. The yield stress of boxthron and mixed boxthron hot-water extractable concentrates ranged from 0.045 to 6.253 Pa and from 0.022 to 8.891 Pa, respectively. The activation energy for the flow of boxthron and mixed boxthorn hot-water extractable concentrates increased from 1.6182 to $2.0543{\times}10^7\;J/kg{\cdot}mol$ and from 1.7057 to $2.1462{\times}10^7\;J/kg{\cdot}mol$ with the concentrations of concentrates, respectively.

• Korean journal of food and cookery science
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• v.21 no.6 s.90
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• pp.936-941
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• 2005

Green tea was extracted with different solvents such as hot water, varying concentrations of ethanol and carbon dioxide fluid. The carbon dioxide fluid extraction of green tea was a very effective extraction method in terms of antioxidant yield and stability. At pressure of 125kgf, antioxidant extract of green tea produced a yield 1.87 and 2.8 times higher than hot water and $95\%$ ethanol extract, respectively. Antioxidant extract of carbon dioxide fluid was also very stable during 7-day storage at 35?.

• The Journal of Engineering Geology
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• v.8 no.2
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• pp.175-188
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• 1998

This paper describes the internal structures and K-Ar ages of fault gouges collected from the Dongnae fault zone. This fault zone is internally zoned and occurs in the multiple fault cores. A fault core consists of thin gouge and narrow cataclastic zones that are bounded by a much thicker damage zone. Intensity of deformation and alteration increases from damage zone through cataclastic zone to gouge zone. It is thought that cataclasis of brittle deformation was the dominant strain-accomodation mechanism in the early stage of deformation to form the gouge zone and that crushed materials in the regions of maximum localization of fault slip subsequently moved by cataclastic flow. Deformation mechanism drastically changed from brittle processes to fluid-assisted flow along the gouge zone as the high porosity and permeability of pulverzied materials during faulting facilitated the influx of the hydrothermal fluids. Subsequently, the fluids reacted with gouge materials to form clay minerals. Fracturing and alteration could have repeatedly taken place in the gouge zone by elevated fluid pressures generated from the reduction of pore volume due to the formation of clay minerals and precipitation of other materials. XRD analysis revealed that the most common clay minerals of the gouge zones are illite and smectite with minor zeolite and kaolinite. Most of illites are composed of 1Md polytype, indicating the products of hydrothermal alteration. The major activities of the Dongnae fault can be divided into two periods based upon K-Ar age data of the fault gouges : 51.4∼57.5Ma and 40.3∼43.6Ma. Judging from the enviromental condition of clay mineral formation, it is inferred that the hydrothermal alteration of older period occured at higher temperature than that of younger period.

• Economic and Environmental Geology
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• v.55 no.6
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• pp.689-699
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• 2022

The Ssangjeon tungsten deposit is located within the Yeongnam Massif. Within the area a number of hydrothermal quartz veins were formed by narrow open-space filling of parallel and subparallel fractures in the metasedimentary rocks as Wonnam formation, Buncheon granite gneiss, amphibolite and/or pegmatite. Mineral paragenesis can be divided into two stages (stage I, ore-bearing quartz vein; stage II, barren quartz 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 arsenopyrite with pyrite; middle, characterized by introduction of wolframite and scheelite with Ti-Fe-bearing oxides and base-metal sulfides; late, marked by Bi-sulfides. Fluid inclusion data show that stage I ore mineralization was deposited between initial high temperatures (≥370℃) and later lower temperatures (≈170℃) from H₂O-CO₂-NaCl fluids with salinities between 18.5 to 0.2 equiv. wt. % NaCl of Ssangjeon 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 ≥370℃ to ≈170℃. Changes in stage I vein mineralogy reflect decreasing temperature and fugacity of sulfur by evolution of the Ssangjeon hydrothermal system with increasing paragenetic time.

• Economic and Environmental Geology
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• v.54 no.6
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• pp.753-765
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• 2021

The Dongwon Au-Ag deposit is located within the Paleozoic Taebaeksan province, Okcheon belt. Mineral paragenesis can be divided into two stages (stage I, ore-bearing quartz veins; stage II, barren carbonate veins) 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 magnetite, pyrrhotite and arsenopyrite; middle, characterized by introduction of electrum and base-metal sulfides with minor sulfosalts; late, marked by argentite, Cu-As (and/or Sb) and Ag-Sb sulfosalts with base-metal sulfides. Fluid inclusion data show that stage I ore mineralization was deposited between initial high temperatures (≥430℃) and later lower temperatures (≤230℃) from fluids with salinities between 6.0 to 0.4 wt. percent equiv. NaCl. The relationship of salinity and homogenization temperature suggest that ore mineralization at Dongwon was deposited mainly due to fluid boiling, cooling and dilution via influx of cooler, more dilute meteoric waters. Changes in stage I vein mineralogy reflect decreasing temperature and fugacity of sulfur by evolution of the Dongwon hydrothermal system with increasing paragenetic time. The Dongwon deposit may represents a Korean-type and/or Au-Ag type mesothermal/epithermal gold-silver deposit.

• Economic and Environmental Geology
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• v.32 no.5
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• pp.435-444
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• 1999

The antimony deposits of the Hyundong mine, located in the northeastern part of the Sobaegsan massif, occur as hydrothermal quartz+carbonate veins and stockworks which fill the fault fractures developed in Precambrian metamOlphic rocks (mainly, granitic gneiss). Hydrothermal alteration occurs commonly in the vicinity of mineralized veins and is characterized by sericitization and silicification. A K-Ar age of alteration sericite is 139.2$\pm$ 4.4 Ma, implying the early Cretaceous age of mineralization, possibly in association with intrusion of nearby acidic dikes (mainly, quartz porphyry). The hydrothermal mineralization occurred in five mineralization stages. These are: (I) stage I, characterized by deposition of chalcedonic quartz; (2) stage II, deposition of quartz with base-metal sulfides and stibnite; (3) stage III, deposition of quartz and carbonates (calcite, dolomite, ankerite, rhodochrosite) with various antimony-bearing minerals such as stibnite, polybasite, berthierite, native antimony, gudmundite and ullmannite; (4) stage IV, deposition of calcite with stibnite; and (5) stage V, deposition of barren calcite. Antimony occurs mostly as stibnite within stages II to IV veins, which has various habits including disseminated, veinlets and euhedral coarse crystals. Fluid inclusion studies indicate that hydrothermal mineralization at Hyundong occurred from the fluids with temperature and salinity of $330^{\circ}$C to 120 and 5.3 wI. % equiv. NaCI. The temperature and salinity of ore fluids systematically decreased with elapsed time in the course of mineralization, possibly due to the influx of larger amounts of meteoric groundwater. The deposition of antimony-bearing minerals occurred at low temperatures «$250^{\circ}$C), mainly due to the cooling and dilution of fluids. Based on the evidence of fluid boiling during the early stage II mineralization, the mineralization occurred under low pressure conditions (about 80 bars, corresponding to depths of about 350 m under hydrostatic pressure regime). Thermodynamic considerations of ore . mineral assemblages indicate that antimony deposition also occurred as the results of decreases in temperature and sulfur fugacity of hydrothermal fluids. Calculated sulfur isotope composition of ore fluids ($\delta^{34}S_{\Sigma s}$=5.4 to 7.8$\textperthousand$) indicates an igneous source of sulfur.

• The Journal of the Petrological Society of Korea
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• v.13 no.4
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• pp.224-237
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• 2004

The anorthositic rocks of the study area are divided into the northern Sancheong and southern Hadong anorthositic rocks depending on the different distribution patterns and lithologies. In order to evaluate the characteristics of the hydrothermal systems developed in the study area, oxygen and hydrogen isotopic compositions of the anorthositic rocks were measured. Oxygen isotopic values of the plagioclase exhibit an interesting spatial distribution. Plagioclase collected from the Sancheong anorthositic rocks in the northern part tends to have a relatively restricted range of $\delta$$^{18/0}$ values between 7.3 and 8.8$\textperthousand$, which are heavier than 'normal' $\delta$$^{18/O}$ value (6-6.5$\textperthousand$) typical for plagioclase of the fresh mantle-derived anorthosite, whereas plagioclase from the southern part is characterized by a wide range of $\delta$$^{18/O}$ values between -4.4 and 8.2$\textperthousand$ and much lighter values than 'normal' value for plagioclase of the fresh mantle-derived anorthosite. Plagioclase from the middle part has $\delta$$^{18/O}$ values heavier than the plagioclase from the southern part, but lighter than that from the northern part. The spatial distribution of $\delta$$^{18/O}$ values suggests that the decoupled hydrothermal flow systems might have been developed in the study area. Meteoric water dominated in the hydrothermal flow systems developed in the southern area, whereas magmatic fluid dominated in the northern area. The relationship between water content and hydrogen isotopic composition of anorthosites shows a positive correlation. The positive correlation indicates that fluids exsolved from magma during magmatic differentiation caused deuteric alteration of anorthositic rocks involving replacement of pyroxenes to amphiboles. After the deuteric alteration, hydrothermal system developed by meteoric water dominated the southern area, and erased record of the hydrothermal system developed by magmatic fluid at earlier stage. However, the development of meteoric hydrothermal system has been limited in the southern area only, and could not affect the Sancheong anorthositic rocks in the northern area. The abundant occurrences of secondary alteration minerals such as sericite, calcite, and chlorite in the southern Hadong anorthosite relative to the northern Sancheong anorthositc seem to be related to the overlapping of two distinct hydrothermal systems in the southern area.

• Journal of the Mineralogical Society of Korea
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• v.23 no.1
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• pp.1-13
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• 2010

The Yugeum deposit in Youngduk in Gyungsangbuk-do is emplaced in the Cretaceous granitoids located in the Northeastem Gyeongsang Basin. Gold-bearing quartz veins filling the fracture with a direction of $N19^{\circ}{\sim}38^{\circ}W$ are most abundantly distributed within the Younghae granodiorite body. The formation of quartz veins can be classified into three main stages: barren quartz stage, auriferous quartz vein stage, and finally the extensive sulfide mineralization stage. Various sulfide minerals such as pyrite, chalcopyrite, galena, sphalerite, and arsenopyrite were precipitated during the hydrothermal gold mineralization process. Gold commonly occurs as fine-grained electrum in sulfides with high Au concentration (up to 93 wt%) compared to Ag. During the early gold mineralization stage, the temperature and pressure of the fluids are in the range of $220{\sim}250^{\circ}C$ and 730~1800 bar, and the oxygen fugacity is between $10^{-27}$ and $10^{-31.7}$ atm. On the other hand, the fluids of the late stage mineralization are characterized by temperature of $290{\sim}350^{\circ}C$ and pressure of 206~472 bar, and the oxygen fugacity is in the range of $10^{-26.3}{\sim}10^{-28.6}$ atm. The sulfur isotope compositions of sulfide minerals are in the range of $0.2{\sim}4.2^{\circ}/_{\circ\circ}$, while the ${\delta}^{34}SH_2S$ values range from 1.0 to $3.7^{\circ}/_{\circ\circ}$. The Ag/Au atomic ratios of electrum ranges from 0.15 to 1.10, and Au content is higher than Ag in most electrum. During the main gold mineralization stage at the relatively high temperature condition and with pH from 4.5 to 5.5, the stability of ${AuCl_2}^-$ increased while the stability of ${Au(HS)_2}^-$ decreased. Considering the pressure estimated in this deposit, the temperature of the ore fluid reached higher than $350^{\circ}C$ and ${AuCl_2}^-$ became an important species for the gold transportation. As mineralization proceeded with decreasing temperature and increasing pH and $f_{o2}$, the precipitation of sulfide minerals and accompanying electrum occurred.