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Econ. Environ. Geol. 2021; 54(6): 753-765

Published online December 28, 2021

https://doi.org/10.9719/EEG.2021.54.6.753

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

Genetic Environments of Dongwon Au-Ag-bearing Hydrothermal Vein Deposit

Sunjin Lee, Sang-Hoon Choi*

Department of Earth and Environmental Sciences, Chungbuk National University, Cheongju 28644, Korea

Correspondence to : *cshoon@cbnu.ac.kr

Received: December 19, 2021; Revised: December 22, 2021; Accepted: December 22, 2021

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

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°C) and later lower temperatures (≤230°C) 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.

Keywords Dongwon Au-Ag deposit, hydrothermal, fluid inclusion, vein deposit

동원 함 금-은 열수 맥상광상의 생성환경

이선진 · 최상훈*

충북대학교 지구환경과학과

요 약

동원광상은 옥천대 북서부 태백산분지 내에 분포하는 조선누층군의 변성암류, 퇴적암류 또는 화성암류 내에 발달된 열극을 충진하여 생성된 함 금-은 열수맥상 광상으로, 괴상 및 각력상 조직과 함께 정동의 발달 등 복합적인 조직적 특성을 보여준다. 동원광상의 맥상 광화작용은 지구조적 운동(tectonic break)에 의하여 광화 1시기(stage I)와 광화 2시기(stage II)로 구분된다. 광화 1시기는 석영맥의 생성과 함께 주된 함 금·은 광물인 에렉트럼(electrum)과 함께 황화광물, 산화광물 및 황염광물 등이 산출한 시기로서, 공생관계와 광물 조합 특성 등에 의하여 세 단계의 광화시기(초기, 중기, 후기)로 구분된다. 광화 1시기의 초기에는 주로 황철석, 자철석, 자류철석, 유비철석 등이 산출되었다. 중기에는 주된 금-은 광화작용이 진행되어 에렉트럼과 함께 섬아연석, 황동석, 방연석 등의 황화광물과 함 은 광물 및 황염광물 등이 산출되었다. 후기에는 황철석, 섬아연석, 방연석 등과 함께 함은·안티몬 광물 등이 산출되었다. 광화 2시기는 주 광화작용 이후의 금속 광화작용이 이루어지지 않은 방해석과 백운석맥의 생성시기이다. 동원광상 광화작용은 초기 고온(≥430℃)의 열수유체 유입으로 시작되어 냉각과 비등작용 및 상대적으로 천부를 순환한 열수유체 또는 천수의 혼입 등에 의하여 ≥430℃~≤230℃의 온도조건에서 6.0 to 0.4 wt. percent NaCl 상당 염농도를 갖는 유체에서 진행되었다. 동원광상의 광물 공생관계 변화는 이러한 열수계의 진화에 의한 온도와 황 분압 조건의 감소 등의 환경변화가 반영된 결과이다. 동원광상은 한국형 금·은 광상 및 금-은 혼합형 광상에 해당하는 중/천열수 광상에 대비된다.

주요어 동원 금-은 광상, 열수, 유체포유물, 맥상광상

Article

Research Paper

Econ. Environ. Geol. 2021; 54(6): 753-765

Published online December 28, 2021 https://doi.org/10.9719/EEG.2021.54.6.753

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

Genetic Environments of Dongwon Au-Ag-bearing Hydrothermal Vein Deposit

Sunjin Lee, Sang-Hoon Choi*

Department of Earth and Environmental Sciences, Chungbuk National University, Cheongju 28644, Korea

Correspondence to:*cshoon@cbnu.ac.kr

Received: December 19, 2021; Revised: December 22, 2021; Accepted: December 22, 2021

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

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°C) and later lower temperatures (≤230°C) 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.

Keywords Dongwon Au-Ag deposit, hydrothermal, fluid inclusion, vein deposit

동원 함 금-은 열수 맥상광상의 생성환경

이선진 · 최상훈*

충북대학교 지구환경과학과

Received: December 19, 2021; Revised: December 22, 2021; Accepted: December 22, 2021

요 약

동원광상은 옥천대 북서부 태백산분지 내에 분포하는 조선누층군의 변성암류, 퇴적암류 또는 화성암류 내에 발달된 열극을 충진하여 생성된 함 금-은 열수맥상 광상으로, 괴상 및 각력상 조직과 함께 정동의 발달 등 복합적인 조직적 특성을 보여준다. 동원광상의 맥상 광화작용은 지구조적 운동(tectonic break)에 의하여 광화 1시기(stage I)와 광화 2시기(stage II)로 구분된다. 광화 1시기는 석영맥의 생성과 함께 주된 함 금·은 광물인 에렉트럼(electrum)과 함께 황화광물, 산화광물 및 황염광물 등이 산출한 시기로서, 공생관계와 광물 조합 특성 등에 의하여 세 단계의 광화시기(초기, 중기, 후기)로 구분된다. 광화 1시기의 초기에는 주로 황철석, 자철석, 자류철석, 유비철석 등이 산출되었다. 중기에는 주된 금-은 광화작용이 진행되어 에렉트럼과 함께 섬아연석, 황동석, 방연석 등의 황화광물과 함 은 광물 및 황염광물 등이 산출되었다. 후기에는 황철석, 섬아연석, 방연석 등과 함께 함은·안티몬 광물 등이 산출되었다. 광화 2시기는 주 광화작용 이후의 금속 광화작용이 이루어지지 않은 방해석과 백운석맥의 생성시기이다. 동원광상 광화작용은 초기 고온(≥430℃)의 열수유체 유입으로 시작되어 냉각과 비등작용 및 상대적으로 천부를 순환한 열수유체 또는 천수의 혼입 등에 의하여 ≥430℃~≤230℃의 온도조건에서 6.0 to 0.4 wt. percent NaCl 상당 염농도를 갖는 유체에서 진행되었다. 동원광상의 광물 공생관계 변화는 이러한 열수계의 진화에 의한 온도와 황 분압 조건의 감소 등의 환경변화가 반영된 결과이다. 동원광상은 한국형 금·은 광상 및 금-은 혼합형 광상에 해당하는 중/천열수 광상에 대비된다.

주요어 동원 금-은 광상, 열수, 유체포유물, 맥상광상

    Fig 1.

    Figure 1.Geological map of the Dongwon deposit (from KIGAM, 1962a, b, c and d) with simplified geologic map of Korea showing the tectonic province and location of the Dongwon deposit.
    Economic and Environmental Geology 2021; 54: 753-765https://doi.org/10.9719/EEG.2021.54.6.753

    Fig 2.

    Figure 2.Photographs of the products of hydrothermal mineralization at Dongwon deposit. Scale bar is 3cm. Abbreviations: ank=ankerite, cal=calcite, gn=galena, kuh=kutnohorite, py=pyrite, qtz=quartz, sl=sphalerite, v=vein.
    Economic and Environmental Geology 2021; 54: 753-765https://doi.org/10.9719/EEG.2021.54.6.753

    Fig 3.

    Figure 3.Mineral paragenesis of the Dongwon Au-Ag deposit.
    Economic and Environmental Geology 2021; 54: 753-765https://doi.org/10.9719/EEG.2021.54.6.753

    Fig 4.

    Figure 4.Photomicrographs of mineral occurrence and assemblages at the Dongwon deposit. Abbreviations: ag=argentite, asp=arsenopyrite, cp=chalcopyrite, el=electrum, gn=galena, py=pyrite, pyr=pyrargyrite, qtz=quartz, sl=sphalerite, tt=tetrahedrite.
    Economic and Environmental Geology 2021; 54: 753-765https://doi.org/10.9719/EEG.2021.54.6.753

    Fig 5.

    Figure 5.Photomicrographs of type I (A, B and D) and type II (C and D) fluid inclusions in vein quartz, Dongwon deposit. Abbreviations: V=vapor phase, L=liquid phase, type I=type I fluid inclusion, type II=type II fluid inclusion.
    Economic and Environmental Geology 2021; 54: 753-765https://doi.org/10.9719/EEG.2021.54.6.753

    Fig 6.

    Figure 6.Histogram of homogenization temperatures(Th) of fluid inclusions in vein quartz of the Dongwon deposit. Abbreviations: Type I=type I fluid inclusion, Type II=type II fluid inclusion.
    Economic and Environmental Geology 2021; 54: 753-765https://doi.org/10.9719/EEG.2021.54.6.753

    Fig 7.

    Figure 7.Histogram of salinities of fluid inclusions in vein quartz of the Dongwon deposit. Abbreviations: Type I=type I fluid inclusion, Type II=type II fluid inclusion.
    Economic and Environmental Geology 2021; 54: 753-765https://doi.org/10.9719/EEG.2021.54.6.753

    Fig 8.

    Figure 8.Homogenization temperature versus salinity diagram for type I and II fluid inclusions in vein quartz of the Dongwon deposit. Abbreviations: Type I=type I fluid inclusion, Type II=type II fluid inclusion.
    Economic and Environmental Geology 2021; 54: 753-765https://doi.org/10.9719/EEG.2021.54.6.753

    Fig 9.

    Figure 9.Pseudo-binary condensed T-XAs section of the Fe-As-S system (Kretschmar and Scott, 1976). Filled triangles and inverted triangles indicate As contents in arsenopyrite, Dongwon deposit. Filled triangles (with pyrrhotite and pyrite) and inverted triangles (with pyrite and sphalerite) indicate As contents of arsenopyrite, Dongwon Au-Ag deposit. Abbreviations: Ap=arsenopyrite, Lo=loellingite, Py=pyrite, Po=pyrrhotite.
    Economic and Environmental Geology 2021; 54: 753-765https://doi.org/10.9719/EEG.2021.54.6.753

    Fig 10.

    Figure 10.Fugacity of Sulfur versus temperature diagram for stage I of Dongwon Au-Ag deposit showing the possible sulfur fugacity and temperature ranges with sulfidation reactions. Abbreviations: Arg=argentite, Asp=arsenopyrite, Hm=hematite, Mt=magnetite, NAg=atomic fraction Ag in electrum, Po=pyrrhotite, Py=pyrite.
    Economic and Environmental Geology 2021; 54: 753-765https://doi.org/10.9719/EEG.2021.54.6.753

    Table 1 . Chemical composition of arsenopyrite from Dongwon deposit.

    sample no.weight percentatomic %
    FeAsSTotalFeAsSTotal
    c2-1-2-138.040.221.8100.035.828.435.8100.0
    c2-1-3-137.038.424.6100.034.026.339.7100.0
    c2-1-3-337.840.621.6100.036.028.635.5100.0
    c2-1-6-135.843.620.6100.034.431.234.4100.0
    c2-1-736.743.819.5100.035.731.433.0100.0
    c2-1-837.343.019.7100.036.030.733.3100.0
    c2-1-1337.741.121.2100.036.029.134.9100.0
    31-10-7-137.141.021.9100.034.929.136.0100.0
    31-7-2-139.337.523.2100.036.526.037.5100.0
    31-7-3-136.842.021.2100.035.129.835.1100.0
    31-7-4-138.340.021.6100.036.327.935.8100.0
    31-8-2-136.640.223.3100.033.928.138.0100.0
    31-8-3-138.737.324.0100.035.625.838.7100.0
    31-8-6-135.143.121.9100.033.530.336.2100.0
    31-8-7-138.539.122.3100.036.127.236.7100.0
    31-3-1-139.438.022.6100.036.526.637.0100.0
    31-3-2-139.237.523.2100.036.325.937.8100.0
    DD32-7-136.839.723.5100.034.427.638.0100.0

    Table 2 . Chemical composition of sphalerite from Dongwon deposit.

    sample no.weight %mole %
    ZnFeMnCdSTotalZnSFeSMnSCdSTotal
    c2-1-8-361.72.30.51.534.6100.593.74.10.91.3100.0
    c2-1-8-461.42.40.40.034.498.695.04.30.70.0100.0
    31-10-3-161.72.90.70.034.8100.093.75.11.20.0100.0
    31-10-4-161.23.00.40.035.5100.094.05.40.70.0100.0
    31-10-5-158.54.40.70.034.598.190.78.01.30.0100.0
    31-10-6-163.22.10.50.034.2100.095.53.70.80.0100.0
    31-9-2-161.13.50.30.035.2100.093.36.20.50.0100.0
    31-9-3-163.52.40.40.033.7100.095.14.20.70.0100.0
    31-9-4-164.12.80.50.032.6100.094.34.80.90.0100.0
    31-9-5-163.72.80.40.033.1100.094.44.90.80.0100.0
    31-11-2-160.72.70.80.035.8100.093.74.91.40.0100.0
    31-11-3-160.94.20.00.034.9100.092.57.50.00.0100.0
    31-11-4-160.24.80.00.035.0100.091.58.50.00.0100.0
    31-8-4-164.71.30.00.034.0100.097.72.30.00.0100.0
    31-8-5-158.23.40.00.038.5100.093.66.40.00.0100.0
    31-6-162.51.80.00.034.899.296.73.30.00.0100.0
    31-6-3-161.02.80.40.035.8100.094.25.00.80.0100.0
    31-3-5-163.32.80.40.033.4100.094.34.90.80.0100.0
    31-3-6-163.42.90.70.033.0100.093.85.01.20.0100.0
    31-3-7-162.12.90.30.034.7100.094.35.20.50.0100.0
    DD32-2-364.22.60.50.032.8100.094.74.40.90.0100.0
    DD32-2-461.83.10.00.035.1100.094.55.50.00.0100.0
    DD32-6-162.62.90.60.033.9100.093.85.21.00.0100.0
    DD32-6-263.22.20.60.034.0100.094.93.91.10.0100.0
    DD32-1-160.73.00.80.035.5100.093.15.41.50.0100.0
    DD32-1-261.83.80.00.034.4100.093.46.60.00.0100.0
    DD32-7-261.93.00.60.034.5100.093.65.31.10.0100.0
    DD32-7-362.34.50.00.033.3100.092.37.70.00.0100.0
    DJ11-3-164.70.50.00.034.8100.099.10.90.00.0100.0
    DJ11-3-265.11.10.00.033.8100.098.11.90.00.0100.0
    DJ11-3-364.00.00.00.036.0100.0100.00.00.00.0100.0
    DJ11-3-460.74.80.00.034.5100.091.68.40.00.0100.0
    DJ11-3-564.41.10.00.034.5100.098.02.00.00.0100.0
    DJ11-4-161.22.20.00.036.6100.096.04.00.00.0100.0
    DJ11-4-262.22.10.00.035.7100.096.33.70.00.0100.0

    Table 3 . Chemical composition of electrum from Dongwon deposit.

    sample noweight %atomic %
    AuAgFeSTotalAuAgAg/Au
    c1-1-159.331.03.06.7100.051.248.81.0
    c1-1-1-165.534.00.50.0100.051.348.70.9
    c2-1-8-260.638.51.00.0100.046.353.71.2
    31-3-3-180.119.30.60.0100.063.336.70.6
    31-3-4-182.216.90.90.0100.072.727.30.4
    31-5-1-172.626.51.00.0100.060.040.00.7
    31-5-2-163.335.90.80.0100.049.150.91.0
    DD32-5-171.428.10.40.0100.058.241.80.7
    DD32-2-172.526.51.00.0100.060.040.00.7
    DD32-2-267.831.30.90.0100.054.245.80.8
    DD32-1-372.827.20.00.0100.059.540.50.7
    11-1-1-156.543.50.00.0100.041.558.51.4

    KSEEG
    Jun 30, 2024 Vol.57 No.3, pp. 281~352

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