Original Article

Econ. Environ. Geol. 2017; 50(2): 85-96

Published online April 30, 2017

https://doi.org/10.9719/EEG.2017.50.2.85

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

Genesis of Bonanza-style Ores in Uichang Area, Changwon City: Geochemical Interpretation by Reaction Path Modeling

Seung-han Lee1, Sang-gun No2 and Maeng-Eon Park1*

1Department of Earth and Environmental Sciences, Pukyong National University, Busan 48513, Korea
2Korea Institute of Geoscience and Mineral Resoures, Daejeon 34132, Korea

Correspondence to : mepark@pknu.ac.kr

Received: March 28, 2017; Revised: April 27, 2017; Accepted: April 28, 2017

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

Gold mineralization of Samjeong and Yongjang gold mines in Uichang area shows characteristics of Bonanza-type gold deposits. Ores are mainly developed along the contact parts between quartz vein and arkosic sandstone beds (Fe-rich bed; Che) in sedimentary rock. Electrum, silver sulfide and sulfate minerals are mainly in the ores. On the other hand, gold mineralization is less developed in cherty rock and andesitic rock than arkosic sandstone. The study highlights characteristics of gold precipitation in the deposit on the basis of numerical modelling of the reactions between the assumed hydrothermal ore fluids with multicomponent heterogeneous equilibrium calculations. Aqueous species, gases and minerals, containing electrum are included in the calculations. The reaction result between hydrothermal ore fluids and arkosic sandstone show that pH increasing in the ore-forming fluid would trigger precipitation of quartz, chlorite, sericite, chalcopyrite, galena, pyrite, electrum, actinolite and feldspar. The numerical modelling also illustrates the drastic increase of pH and desulfidation lead to precipitation of electrum. Ag/Au ratios in the ore vary with pH conditions and subsequently precipitation of silver-bearing sulfides such as acanthite and polybasite. The modelling of the reaction between andesitic rock and ore-forming fluid shows that mineral assemblages of the case are analogous to ones of the reaction between arkosic sandstone and fluid except the latter has little portion of electrum. The abovementioned modelling results suggest that gold-silver mineralization is bounded by host rocks at the study area.

Keywords Bonanza-type gold deposit, electrum, wall rock control, reaction path modeling, Uichang area

창원시 의창지역 보난자형 금광상 성인: 반응경로 모델링에 의한 지구화학적 해석

이승한1 ·노상건2 ·박맹언1*

1부경대학교 지구환경과학과, 2한국지질자원연구원 자원탐사개발연구센터

요 약

Article

Original Article

Econ. Environ. Geol. 2017; 50(2): 85-96

Published online April 30, 2017 https://doi.org/10.9719/EEG.2017.50.2.85

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

Genesis of Bonanza-style Ores in Uichang Area, Changwon City: Geochemical Interpretation by Reaction Path Modeling

Seung-han Lee1, Sang-gun No2 and Maeng-Eon Park1*

1Department of Earth and Environmental Sciences, Pukyong National University, Busan 48513, Korea
2Korea Institute of Geoscience and Mineral Resoures, Daejeon 34132, Korea

Correspondence to:mepark@pknu.ac.kr

Received: March 28, 2017; Revised: April 27, 2017; Accepted: April 28, 2017

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

Gold mineralization of Samjeong and Yongjang gold mines in Uichang area shows characteristics of Bonanza-type gold deposits. Ores are mainly developed along the contact parts between quartz vein and arkosic sandstone beds (Fe-rich bed; Che) in sedimentary rock. Electrum, silver sulfide and sulfate minerals are mainly in the ores. On the other hand, gold mineralization is less developed in cherty rock and andesitic rock than arkosic sandstone. The study highlights characteristics of gold precipitation in the deposit on the basis of numerical modelling of the reactions between the assumed hydrothermal ore fluids with multicomponent heterogeneous equilibrium calculations. Aqueous species, gases and minerals, containing electrum are included in the calculations. The reaction result between hydrothermal ore fluids and arkosic sandstone show that pH increasing in the ore-forming fluid would trigger precipitation of quartz, chlorite, sericite, chalcopyrite, galena, pyrite, electrum, actinolite and feldspar. The numerical modelling also illustrates the drastic increase of pH and desulfidation lead to precipitation of electrum. Ag/Au ratios in the ore vary with pH conditions and subsequently precipitation of silver-bearing sulfides such as acanthite and polybasite. The modelling of the reaction between andesitic rock and ore-forming fluid shows that mineral assemblages of the case are analogous to ones of the reaction between arkosic sandstone and fluid except the latter has little portion of electrum. The abovementioned modelling results suggest that gold-silver mineralization is bounded by host rocks at the study area.

Keywords Bonanza-type gold deposit, electrum, wall rock control, reaction path modeling, Uichang area

창원시 의창지역 보난자형 금광상 성인: 반응경로 모델링에 의한 지구화학적 해석

이승한1 ·노상건2 ·박맹언1*

1부경대학교 지구환경과학과, 2한국지질자원연구원 자원탐사개발연구센터

Received: March 28, 2017; Revised: April 27, 2017; Accepted: April 28, 2017

요 약

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

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