Studies on Fluid Inclusion and Stable Isotope of the Namsan Gold-Silver Mine

남산 금-은광산의 유체포유물 및 안정동위원소 연구

  • Kim, Se-Hyun (Department of mineral and mining engineering, Sangji University) ;
  • Choi, Sang-Hoon (Center for Mineral Resources Research, Korea Univ.,)
  • 김세현 (상지대학교 자원공학과) ;
  • 최상훈 (전략광물자원연구센터)
  • Received : 1996.02.07
  • Published : 1996.04.30

Abstract

Electrum-sulfide minerals of the Namsan Au-Ag mine were deposited in two stages of quartz and calcite veins that fill fault planes in Mesozoic granitic rocks (230~155 Ma). The K/Ar radiometric dating of hydrothermal sericite indicates that mineralization is early Cretaceous age ($127{\pm}3.0Ma$). Mineralogic, fluid inclusion and sulfur isotopic data show that ore minerals were deposited at temperatures between $340^{\circ}C$ and $200^{\circ}C$ from fluid with salinities of 3 to 6 equiv. wt % NaCl. Evidence of fluid boiling (and $CO_2$ effervescence) indicates a maximum pressures of 100 bars. The formation temperature and $fs_2$, of Au-mineralization from the Namsan mines are mainly $280{\sim}230^{\circ}C$ and $10^{-11}{\sim}10^{-13}$ atm, respectively. Au deposition was likely a result of boiling caused to chemical change (pH, $f_{O2}$, ${\Sigma}_{H_2S{\cdot}{\cdot}}$) of ore-fluids. Sulfur isotope composition of sulfide minerals (${\delta}^{34}S=5.1$ to 8.2‰) are consistent with ${\delta}^{34}S_{{\Sigma}{H2S}}$ value of +6 to +7‰, suggesting an igneous source of sulfur partially mixed with wall-rock sulfur.

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Acknowledgement

Supported by : 학술진흥재단