• The Journal of the Petrological Society of Korea
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• v.8 no.1
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• pp.46-55
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• 1999

Fluid inclusions in granite and hydrothermal quartz indicate that three fluids have affected the Sannae granite. The earliest fluid is represented by three-phase aqueous fluid inclusions with high salinity (38 to 46 wt.% NaCl equiv.). It was exsolves from a crystallizing melt and trapped at a relatively high-pressure condition. The secong fluid is represented by two-phase aqueous fluid inclusion with low entectic temperatures (< $-40^{\circ}C$). low- to moderate salinity (3 to 24.0 wt.% NaCl equiv.) and high homogenization temperatures$ ($309^{\circ}C$$473^{\circ}C$)($. This fluid was trapped at higher pressures than 300-500 bars and precipitated molybdenite and wolframite in quartz veins. It was probably generted by fluid-host rock interactions since they show a wide range of salinity within a narrow range of homogenization temperatures. The final fluid is represented by an aquenous fluid boiling that separated into high-salinity (34-38 wt.% NaCl equiv.) and low-salinity fluid (0 to 8.7 wt.%) at $303-376^{\circ}C$ and 50-150 bars. These boiling fluids precipitated euhedral quartz in miarolitic cavities. The compositions of the final fluid was rather complex in the $H_2$O-NaCl-KCI-$FeCl_2$ system. The Sannae granite was a locus for repeated fluid events including magmatic fluids during the final stage of crystallization, the convection of hydrothermal fluids causing a fluid ascending, fluid boiling, and the local W-Mo mineralization and formation of miarolitic cavities due to thermal, tectonic and compositional properties of the felsic granite.

• Economic and Environmental Geology
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• v.33 no.1
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• pp.19-30
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• 2000

The Sannae-Eonyang granitic rocks are a large fossil hydrothermal system containing the Sannae Mo-W fissure-vein type and the Eonyang amethyst deposits in the southeastern Kyongsang Basin. They evolved through similar stages showing the similarities in chemical and mineralogical compositions, fractionation trends and early magmatic fluids. Major, trace and rare earth element(REE) variations can be accounted for fractional crystallization combined with variable degrees of metasomatism. Based on the aqueous fluids exsolved directly from the crystallizing melt, the Sannae-Eonyang granitic rocks were emplaced at similar depth or pressure conditions. High temperature fluid interaction with the granitic rocks affects the elements such as K, Na, Rb, Ba, Sr, Eu, and heavy REE (HREE) mostly through feldspar re-equilibration. Although hydrothermal fluids produced partly positive Eu anomalies and HREE depletion in the granitic rocks at the Sannae Mo-W mine, the chemical concentrations defining fractionnation trends have survived the effects of alteration. Aqueous fluids exsolved from the crystallizing melt appears to be widespread, whereas fluids of moderate to low salinity and low-density with relatively high homogenization temperatures and $Co_2$-rich fluids appear to be mainly restricted and responsible for Mo-W and amethyst mineralization, respectively. Hydrothermal system of the Sannae-Eonyang granitic rocks represents repeated fluid events; from exsolution of aqueous fluids from the crystallizing melt, through fluid immiscibility and meteoric convection to later mineralization.

• Economic and Environmental Geology
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• v.46 no.1
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• pp.11-19
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• 2013

The Daehwa Mo-W deposit is located within the Gyeonggi massif. Quartz and calcite vein mineralization occurred in the Precambrian gneiss and Jurassic granites. Three main types (Type I: liquid-rich $H_2O$ type, Type II: vapor-rich $H_2O$ type, Type III: $CO_2-H_2O$ type) of fluid inclusions were observed and are classified herein based on their phase relations at room temperature. Within ore shoots, type III fluid inclusions have been classified into four subtypes (type IIIa, IIIb, IIIc and IIId) based on their volume percent of aqueous and carbonaceous ($CO_2$) phase at room temperatures combined with their total homogenization behavior and homogenization behavior of $CO_2$ phase. Homogenization temperatures of primary type I fluid inclusions in the quartz range from $374^{\circ}C$ to $161^{\circ}C$ with salinities between 13.6 and 0.5 equiv. wt.% NaCl. Homogenization temperatures of primary type III fluid inclusions in quartz of main generation, are in the range of $303^{\circ}C$ to $251^{\circ}C$. Clathrate melting temperatures of the type III fluid inclusions were 7.3 to $9.5^{\circ}C$, corresponding to salinities of 5.2 to 1.0 equiv. wt. % NaCl. Melting and homogenization temperatures of $CO_2$ phase of type III fluid inclusions were -57.4 to $-56.6^{\circ}C$ and 29.0 to $30.8^{\circ}C$, respectively. Fluid inclusion data indicate a complex geochemical evolution of hydrothermal fluids. The Daehwa early hydrothermal system is characterized by $H_2O-CO_2$-NaCl fluid at about $400^{\circ}C$. The main mineralization occurred by $CO_2$ immiscibility at temperatures of about 300 to $250^{\circ}C$. At the late base-metal mineralization aqueous fluid formed by mixing with cooler and less saline meteoric groundwater.