자원환경지질 (Economic and Environmental Geology)

  • 제32권2호
  • /
  • Pages.129-139
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  • 1999
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  • 1225-7281(pISSN)
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  • 2288-7962(eISSN)
대한자원환경지질학회 (The Korean Society of Economic and Environmental Geology)
권호 표지

베트남 짜봉(Trabong) 지역의 열수 금 광화작용 : 광물 및 지화학적 연구

Hydrothermal Gold mineralization of the trabong district, vietnam : Mineralogical and geochemical study

  • 발행 : 1999.04.01
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초록

베트남 짜봉 지역의 열수 금광상은 단일 광화 시기의 석영$\pm$방해석 맥으로 산출되며, 원생대의 Chulai Complex와 Kham Duc Formation을 이루는 ga 흑연 편마암 및 편암 내의 단층 열극을 충진하고 있다. 광석의 금 품위는 1.3~92.4g/ton 이다. 광석 광물은 매우 단순하여 주로 황철석 및 미량의 base-metal 황화물과 에렉트럼으로 구성된다. 금은 다음과 같은 두 유형의 공생군에서 산출된다. :1) 함철량이 풍부함 섬아연석+엘렉트럼 공생군으로서 황철석 내의 내포물로 산출되며 초기에 해당;2) 함철량이 낮은 섬아연석+방연석+엘렉트럼 공생군으로서 황철석의 단열을 따라 산출되며 후기에 해당. 유체포유물자료 및 공생광물군에 대한 열역학적 고찰에 의하면, 광화작용은 H\sub 2\O-CO\sub2\(-CH\sub 4\)-NaCl 계 유체로부터 230~42$0^{\circ}C$의 고온에서 진행되었으며 광화 유체의 황 분압은 10\sup -6\-10\sup -10\atm 이었다. 광석 광물의 침전은 주로 CO\sub 2\ 개스의 일탈을 수반한 유체 불혼화에 의해 진행되었다. 광화 유체 중 물의 산소 및 수소 동위원소 조성과 황화광물의 황 도위 원소 조성 및 유체포유물 CO\sub 2\ 의 탄소 동위원소 조성은 본 연구 지역의 중-고온형 금 광화작용이 마그마성 유체로부터 진행되었음을 지시한다.

Hydrothermal gold deposits of the Trabong district in Vietnam occur as single-stage quartz $\pm$ calcite veins (0.3-1.2 m thick) which fill fault fractures in graphite-bearing gneiss and schist of the Chulai Complex and Kham Duc Formation of the Proterozoic age. Ore grades are 1.3 to 92.4 g/ton Au. Ore mineralogy is very simple, consisting mainly of pyrite with minor amounts of base-metal sulfides and electrum. Gold grains occur in two assemblages as follows: (1) early, Fe-rich (7.2-10.4 mole % FeS) sphalerite + electrum (50.4-64.3 atom % Au) assemblage occurring as inclusions in pyrite; (2) late, Fe-poor «4.7 mole % FeS) sphalerite + galena + electrum (47.6-81.7 atom % Au) assemblage occurring along fractures of pyrites. Based on fluid inclusion data and thermochemical considerations of ore mineral assemblages, ore minerals were formed at high temperatures (about $230^{\circ}C$ to $420^{\circ}C$) from $H_{2}O-CO_{2}(-CH_{4})$-NaCI fluids with the sulfur fugacity of about $10^{-6}$ to $10^{-10}$ atm. Fluid inclusion data also indicate that ore mineralization occurred mainly as a result of fluid unmixing accompanying $CO_2$ effervescence. Calculated oxygen and measured hydrogen isotope compositions of mineralizing waters (${\delta}^{18}O_{V-SMOW}$ values = 5.3 to 8.6$\textperthousand$, ${\delta}D_{V-SMOW}$ values = - 60 to - 52$\textperthousand$), along with the sulfur isotope compositions of vein sulfides (${\delta}^{34}S_{CDR}$ values = - 1.2 to 2.8$\textperthousand$) and carbon isotope compositions of inclusion $CO_2$ (${\delta}^{13}C_{PDB}$ values = - 4.7 to - 2.0$\textperthousand$) indicate that the high temperature (mesohypothermal) gold mineralization formed from a magmatic fluid.

키워드

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