Economic and Environmental Geology (자원환경지질)

The Korean Society of Economic and Environmental Geology (대한자원환경지질학회)
권호 표지

Stable Isotope and Fluid Inclusion Studies of the Daebong Gold-silver Deposit, Republic of Korea

대봉 금-은광상에 대한 유체포유물 및 안정동위원소 연구

  • 유봉철 (충남대학교 자연과학대학 지질환경과학과) ;
  • 이현구 (충남대학교 자연과학대학 지질환경과학과) ;
  • 김상중 (충남대학교 자연과학대학 지질환경과학과)
  • Published : 2003.12.01
Download PDF
⟨ Previous Next ⟩

Abstract

The Daebong gold-silver deposit consists of mesothermal massive quartz veins thar are filling the fractures along fault shear (NE, NW) Bones within banded or granitic gneiss of Precambrian Gyeonggi massif. Based on vein mineralogy, ore textures and paragenesis, ore mineralization of this deposits is composed of massive white quartz vein(stage I) which was formed in the same stage by multiple episodes of fracturing and healing, and transparent quartz vein(stage II) which is separated by a major faulting event. Stage I is divided into the 3 substages. Ore minerals of each substages are as follows: 1) early stage I=magnetite, pyrrhotite, arsenopyrite, pyrite, sphalerite, chalcopyrite, 2) middle stage I=pyrrhotite, arsenopyrite, pyrite, marcasite, sphalerite, chalcopyrite, galena, electrum and 3) late stage I=pyrite, sphalerite, chalcopyrite, galena, electrum, argentite, respectively. Ore minerals of the stage II are composed of pyrite, sphalerite, chalcopyrite, galena and electrum. Systematic studies (petrography and microthermometry) of fluid inclusions in stage I and II quartz veins show fluids from contrasting physical-chemical conditions: 1) $H_2O-CO_2-CH_4-NaCl{\pm}N-2$ fluid(early stage I=homogenization temperature: 203∼3$88^{\circ}C$, pressure: 1082∼2092 bar, salinity: 0.6∼13.4 wt.%, middle stage I=homogenization temperature: 215∼28$0^{\circ}C$, salinity: 0.2∼2.8 wt.%) related to the stage I sulfide deposition, 2) $H_2O-NaCl{\pm}CO_2$ fluid (late stage I=homogenization temperature: 205∼2$88^{\circ}C$, pressure: 670 bar, salinity: 4.5∼6.7 wt.%, stage II=homogenization temperature: 201-3$58^{\circ}C$, salinity: 0.4-4.2 wt.%) related to the late stage I and II sulfide deposition. $H_2O-CO_2-CH_4-NaCl{\pm}N_2$ fluid of early stage I is evolved to $H_2O-NaCl{\pm}CO_2$ fluid represented by the $CO_2$ unmixing due to decrease in fluid pressure and is diluted and cooled by the mixing of deep circulated meteoric waters ($H_2O$-NaCl fluid) possibly related to uplift and unloading of the mineralizing suites. $H_2O-NaCl{\pm}CO_2$ fluid of stage II was hotter than that of late stage I and occurred partly unmixing, mainly dilution and cooling for sulfide deposition. Calculated sulfur isotope compositions ({\gamma}^{34}S_{H2S}$) of hydrothermal fluids (3.5∼7.9%o) indicate that ore sulfur was derived from mainly an igneous source and partly sulfur of host rock. Measured and calculated oxygen and hydrogen isotope compositions ({\gamma}^{18}O_{H_2O}$, {\gamma}$D) of ore fluids (stage I: 1.1∼9.0$\textperthousand$, -92∼-86{\textperthansand}$, stage II: 0.3{\textperthansand}$, -93{\textperthansand}$) and ribbon-banded structure (graphitic lamination) indicate that mesothermal auriferous fluids of Daebong deposit were two different origin and their evolution. 1) Fluids of this deposit were likely mixtures of $H_2O$-rich, isotopically less evolved meteoric water and magmatic fluids and 2) were likely mixtures of $H_2O$-rich. isotopically heavier $\delta$D meteoric water and magmaticmetamorphic fluids.

대봉 금-은광상은 선캠브리아기 경기육괴의 호상 또는 화강편마암내에 발달된 단열대(NE, NW)를 따라 충진한 중열수 괴상석영맥광상이다. 광석광물의 산출조직과 공생관계에 의하면, 이 광상의 광화작용은 여러번의 단열작용에 의해 형성된 괴상백색석영맥(광화I시기)과 투명석영시기(광화II시기)로 구성된다. 광화I기는 3회의 substages로 구분된다. 각 substage의 광석광물은 다음과 같다: 1) 광화I시기 조기=자철석, 자류철석, 유비철석, 황철석, 섬아연석, 황동석, 2) 광화I시기 중기=자류철석, 유비철석, 황철석, 백철석, 섬아연석, 황동석, 방연석, 에렉트럼과 3) 광화I시기 말기=황철석, 섬아연석, 황동석, 방연석, 에렉트림, 휘은석. 광화II시기의 광석광물로는 황철석, 섬아연석, 황동석, 방연석 및 에렉트럼이 관찰된다. 유체포유물의 체계적 연구에 의하면, 물리-화학적 상태가 상반되는 유체가 관찰된다: 1) 광화 I시기 조기와 중기 광석광물 정출과 관련된 $H_2O-CO_2-CH_4-NaCl{\pm}N_2$ 유체(조기=균일화온도: 203∼388^{\circ}C$, 압력: 1082∼2092 bar, 염농도: 0.6∼13.4wt.%, 중기=균일화온도: 215∼280^{\circ}C$, 염농도: 0.2∼2.8wt.%), 2) 광화I시기 말기와 광화II시기 광석광물과 관련된 $H_2O-NaCl{\pm}CO_2$ 유체(광화I시기 말기=균일화온도: 205∼2$88^{\circ}C$, 압력: 670bar, 염농도: 4.5∼6.7wt.%, 광화II시기=균일화온도: 201∼358^{\circ}C$, 염농도: 0.4∼4.2wt.%)이다. 광화I시기 조기의 $H_2O-CO_2-CH_4-NaCl{\pm}N_2$계 유체는 유체압력의 차이에 의해 CO_2$ 상분리가 일어났으며 광화작용이 진행됨에 따라 $H_2O-NaCl{\pm}CO_2$계 유체로 진화되었다. 또한 여기에 기원이 다른 $H_2O$-NaCl계 유체의 유입에 의해 혼입 및 희석작용으로 염농도의 감소가 있었다고 생각된다. 광화II시기 좀더 가열된 $H_2O-NaCl{\pm}CO_2$ 계 유체는 불혼합, 희석 및 냉각작용이 있었던 것으로 생각된다. 열수용액의 {\gamma}^{34}$S__{H2S}$ 값은 3.5∼7.9{\textperthansand}$로서 황은 주로 화성기원이지만 부분적으로 모암내의 황에서도 기원되었다고 생각된다. 광화유체의 산소({\gamma}^{18}O_{H2O}$)와 수소({\gamma}$D)안정동위원소값이 광화I시기에는 각각 11∼9.${\textperthansand}$, -92∼-86${\textperthansand}$, 광화 II시기에는 각각 0.3${\textperthansand}$(${\gamma}^{18}O_{H2O}$),-93${\textperthansand}$({\gamma}$D)이며, 리본-호상구조를 보이는 것으로 보아 대봉광상의 광화유체에 대한 기원과 진화과정을 두 가지로 생각할 수 있다. 1) 마그마유체로부터 광화작용이 진행됨에 따라 계속적인 순환수의 혼입이 있었으며 2) 조기 마그마${\pm}$변성유체에서 유체압력의 차에 의해 $CO_2$ 상분리와 더불어 계속적인 ${\gamma}$D가 높은 순환수의 혼입이 있었던 것으로 해석할 수 있다.있다.

Keywords

References

  1. 지질학회지 v.24 남한의 지하수 및 강수의 안정동위원소조성 김규한;中井信之
  2. 광산지질 v.25 충남 대봉 금-은광상에서 산출되는 광석광물과 광상의 생성 환경 이현구;유봉철;김상중
  3. Computers Geosci. v.23 Clathrates: Computer programs to calculate fluide inclusion V-X properties using clathrate melting temperatures Bakker,R.J. https://doi.org/10.1016/S0098-3004(96)00073-8
  4. Short course of the working group inclusion in minerals Microthermometric investigations: Th and Tm. practical and theoretical aspects Belkin,H.E.
  5. Econ. Geol. v.78 A method of calculating fluid inclusion volumes based on vapor bubble diameters and P-V-T-X properties of inclusion fluids Bodnar,R.J. https://doi.org/10.2113/gsecongeo.78.3.535
  6. Jour. Structural. Geology v.14 Paleoseismic events recorded in Archean goldquartz vein networks, Vald'Or Abitibi, Quebec. Boullier,A.M.G.;Michot,A.,Pecher;Barres,O. https://doi.org/10.1016/0191-8141(92)90054-Z
  7. Geochim. Cosmochim. Acta v.47 Calculation of the thermodynamic and geochemical consequences of nonideal mixing in the system H₂O-CO₂-NaCI on phase relations in geologic systems: Equation of state for H₂O-CO₂-NaCI fluids at high pressures and temperatures Bowers,T.S.;Helgeson,H.C. https://doi.org/10.1016/0016-7037(83)90066-2
  8. Am. Mineralogist v.74 FLINCOR: A microcomputer program for the reduction and investigation of fluid-inclusion data Brown,P.E.
  9. Mineralium Deposita v.28 Gold mineralisation at the Lady Bountiful mine, western Australia: An example of a granitoid-hosted Archean 1 Iode gold deposit Cassidy,K.F.;Bennett,J.M. https://doi.org/10.1007/BF02431598
  10. Econ. Geol. v.74 Gas hydrates in Co₂-bearing fluid inclusions and the use of freezing data for estimation of salinity Collins,P.L.F. https://doi.org/10.2113/gsecongeo.74.6.1435
  11. Am. Jour. Sci. v.290 Fluid inclusion evidence for P-V-T-X evolusion of hydrothermal solutions in late-Alpine gold-quarz veins at Brusson, Val D'ayas, Northwest Italian Alps Diamond,L.W. https://doi.org/10.2475/ajs.290.8.912
  12. Short course of the working group inclusion in minerals Introduction to phase relations of CO₂-H₂O fluid inclusions Diamond,L.W.
  13. Igneous and metamorphic reactions involving gas equilibrtia: in Researches in Geochemistry v.2 Eugster,H.P.;Skippen,G.B.;Abelson,P.H.(ed.)
  14. Econ. Geol. v.86 Oxygen, hydrogen and sulphur isotope studies in the Juneau gold belt, southeastern Alaska: Constraints on the origin of hydrothermal fluids Goldfarb,RJ.;Newberry,R.J.;Pickthom,W.J.;Gent,C.A. https://doi.org/10.2113/gsecongeo.86.1.66
  15. Geochim. Cosmochim. Acta. v.48 An algorithm for finding composition, molar volume and isochors of CO₂-CH₄fluid inclusions from Th and Tfm(for Thhttps://doi.org/10.1016/0016-7037(84)90328-4
  16. Geochim. Cosmochim. Acta. v.40 Phase equilibria in fluid inclusions from the Khtada Lake metamorphic complex Hollister,L.S.;Burruss,R.C. https://doi.org/10.1016/0016-7037(76)90174-5
  17. Adv., Physical Geochemistry v.1 Volatile interactions in magmas. In thermodynamics of minerals and melts Holloway,J.R.;Newton,R.C.(ed.);Navrotsky,A.(ed.);Wood,B.J.(ed.) https://doi.org/10.1007/978-1-4612-5871-1_13
  18. Geochim. Cosmochim. Acta. v.45 Methane: an equation of state with application to the ternary system H₂O- CO₂-CH₄ Jacobs,G.K.;Kerrick,D.M. https://doi.org/10.1016/0016-7037(81)90035-1
  19. Am. Jour. Sci. v.281 A modified Redlich-Kwong equation for H₂O, CO₂, and H₂O-CO₂mixtures at elevated pressures and temperatures Kerrick,D.M.;Jacobs,G.K. https://doi.org/10.2475/ajs.281.6.735
  20. Geochemistry v.15 A study on hydfrogen, oxygen and sulfur isotopic ratios of the hot spring waters in South Korea Kim,K.H.;Nakai,N.
  21. Geochim. Cosmochim. Acta. v.53 Synthetic fluid inclusions: IX. Cirtical PVTX properties of NaC1-H₂O solutions Knight,C.L.;Bodnar,R.J.
  22. Geochim. Cosmochim. Acta. v.43 Oxygen isotope fractionation in the system quartzalbite-anorthite-water Matsuhisa,Y.;Goldsmith,R.;Clayton,R.N. https://doi.org/10.1016/0016-7037(79)90099-1
  23. Ore geology Reviews v.12 P-T-t-deformationfluid characteristics of lode gold deposits: Evidence from alteration systematics McCuaig,T.C.;Kerrich,R.
  24. Computers Geosci. v.11 Fortran programs for calculation of fluid properties from microthermometric data on fluid inclusions Nicholls,J.;Crawford,M.L. https://doi.org/10.1016/0098-3004(85)90090-1
  25. Geochemistry of hydrothermal ore deposits(2nd ed.) Isotopes of sulfur and carbon. H.L. Barnes Ohmoto,H.;Rye,R.O.
  26. Chem. Geology v.37 Fluid immiscibility in natural processes: Use and misuse of fluid inclusion data Ⅱ. Interpretation of fluid inclusion data in terms of immiscibility Ramboz,C.;Pichavant,M.;Weisbrod,A. https://doi.org/10.1016/0009-2541(82)90065-1
  27. Geochim. Cosmochim. Acta v.49 The P-V-T-X-$f_{02}$ evolution of H₂O-CO₂-CH₄-bearing fluid in a wolframite vein: Reconstruction from fluid inclusion studies Ramboz,C.;Schnapper,D.;Dubessy,J. https://doi.org/10.1016/0016-7037(85)90205-4
  28. Mineral. Soc. America v.12 Fluid inclusion. Reviews in mineralogy Roedder,E.
  29. Econ. Geol. v.83 Gold-rich mesothermal vein deposits of the Republic of Korea: Geochemical studies of the Jungwon gold area Shelton,K.L.;So,C.S.;Chang,J.S. https://doi.org/10.2113/gsecongeo.83.6.1221
  30. Geology v.16 High angle reverse faults, fluid-pressure cycling, and mesothermal gold-quartz deposits Sibson,R.H.;Robert,F.;Poulsen,K.H. https://doi.org/10.1130/0091-7613(1988)016<0551:HARFFP>2.3.CO;2
  31. Econ. Geol. v.92 Jurassic mesothermal gold mineralization of the Samhwanghak mine, Youngdong area, Republic of Korea: Constraints on hydrothermal fluid geochemistry So,C.S.;Yun,S.T. https://doi.org/10.2113/gsecongeo.92.1.60
  32. Jour. Korean Inst. Mining Geol. v.26 Mesothermal gold-silver mineralization at the Bodeok mine, Boseong area: A fluid inclusion and stable isotope study So,C.S.;Yun,S.T.;Kim,S.H.;Youm,S.J.;Heo,C.H.;Choi,S.G.
  33. Geochim. Cosmochim. Acta. v.54 Isochoric phase diagrams in the systems CO₂-CH₄and CO₂-N₂: Application to fluid inclusions Van Den Kerkhof,A.M. https://doi.org/10.1016/0016-7037(90)90358-R
  34. Short course of the working group inclusion in minerals Phase transitions and density calculation in the Co₂-CH₄-N₂system Van Den Kerkhof,A.M.;Thiery,R.
  35. Geology v.24 Pressure fluctuations, phase separation and gold precipitation during seismic fracture propagation Wilkinson,J.J.;Johnson,J.D. https://doi.org/10.1130/0091-7613(1996)024<0395:PFPSAG>2.3.CO;2
  36. Chem. Geology v.64 Determination of the homogenization temperatures and densities of supercitical fluids in the system NaCI-KCI-CaCI₂-H₂O using synthetic fluid inclusions Zhang,Y.G.;Frantz,J.D. https://doi.org/10.1016/0009-2541(87)90012-X