Original Article

Econ. Environ. Geol. 2017; 50(4): 287-302

Published online August 31, 2017

https://doi.org/10.9719/EEG.2017.50.4.287

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

Genetic Environments of the High-purity Limestone in the Upper Zone of the Daegi Formation at the Jeongseon-Samcheok Area

Chang Seong Kim1*, Seon-Gyu Choi1, Gyu-Bo Kim1, Jeonggeuk Kang1, Kyeong Bae Kim2, Hagsoo Kim3, Jeongsang Lee3 and In-Chang Ryu4

1Department of Earth and Environmental Sceinces, Korea University, Seoul 02841, Korea
2Gangwon Material Inc., Gangwon 50018, Korea
3Geogeny Consultants Group Inc., Seoul 06585, Korea
4School of Earth System Sciences, Kyeongbook National University, Daegu 41566, Korea

Correspondence to : cskim72@korea.ac.kr

Received: July 27, 2017; Revised: August 28, 2017; Accepted: August 30, 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

The carbonate rocks of the Daegi Formation are composed of the limestone at the upper and lower zones, and the dolomite at the middle zone, in which the upper zone has higher CaO content than others. The colors of carbonate rock in the Daegi Formation can be divided into five types; white, light brown, light grey, grey, and dark grey. The white to light grey colored rocks correspond to the high purity limestone with 53.15 ~ 55.64 wt. % CaO, and the light brown colored rocks contain 20.71 ~ 21.67 wt. % MgO. The bleaching of carbonate rocks are not related to CaO composition of the rocks, as light grey rocks tend to be higher in CaO content than those of the white rocks at the lower zone. The pelitic components are also occasionally increased in white limestone than light grey one. Al2O3 is one of the most difficult content to remove during hydrothermal processes, so the interpretation that the limestone is purified together with hydrothemral bleaching, has little merit. The wide range (over 16 ‰) of δ18OSMOW, smaller variation (within 2 ‰) of δ13CPDB are apparent in both the upper and lower zones, which indicate the Daegi Formation had been affected overall by hydrothermal fluids. The K-Ar isotopic age of hydrothermal alteration in the GMI limestone mine is 85.1 ± 1.7 Ma. Gradual change from grey through light grey to white limestone is accompanied by lower oxygen stable isotope values, which is major evidence that the hydrothermal effect is the main process of the bleaching. Although the Daegi Formation has suffered from hydrothermal activity and increase in whiteness, there is no clear evidence demonstrating the relationship between bleaching and high purity of limestone. The purification of limestone has nothing to do with the hydrothermal activity in this area. Instead, it should be considered that the change of sedimentary environment related to see-level fluctuation which can prevent deposition of pelitic components especially Al2O3 contrbuted to the formation of the high purity limestone in the upper zone of the Daegi Formation. Considering the evidences such as increase in CaO content of limestone by depth, gradual change from calcite to dolomite at the lower zones, and occurring the high purity limestone at the upper zone, the interpretation of sequence stratigraphic aspect to the formation of the high purity Daegi limestone appears to be more suitable than that of hydrothermal alteration origin.

Keywords Daegi Formation, high-purity limestone, Jeongseon, GMI mine, genetic environment

정선-삼척 일대 대기층 상부 고품위 석회석의 생성환경

김창성1* ·최선규1 ·김규보1 ·강정극1 ·김경배2 ·김학수3 ·이정상3 ·유인창4

1고려대학교 지구환경과학과, 2강원머티리얼, 3지오제니 컨설턴트, 4경북대학교 지구시스템과학부

요 약

Article

Original Article

Econ. Environ. Geol. 2017; 50(4): 287-302

Published online August 31, 2017 https://doi.org/10.9719/EEG.2017.50.4.287

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

Genetic Environments of the High-purity Limestone in the Upper Zone of the Daegi Formation at the Jeongseon-Samcheok Area

Chang Seong Kim1*, Seon-Gyu Choi1, Gyu-Bo Kim1, Jeonggeuk Kang1, Kyeong Bae Kim2, Hagsoo Kim3, Jeongsang Lee3 and In-Chang Ryu4

1Department of Earth and Environmental Sceinces, Korea University, Seoul 02841, Korea
2Gangwon Material Inc., Gangwon 50018, Korea
3Geogeny Consultants Group Inc., Seoul 06585, Korea
4School of Earth System Sciences, Kyeongbook National University, Daegu 41566, Korea

Correspondence to:cskim72@korea.ac.kr

Received: July 27, 2017; Revised: August 28, 2017; Accepted: August 30, 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

The carbonate rocks of the Daegi Formation are composed of the limestone at the upper and lower zones, and the dolomite at the middle zone, in which the upper zone has higher CaO content than others. The colors of carbonate rock in the Daegi Formation can be divided into five types; white, light brown, light grey, grey, and dark grey. The white to light grey colored rocks correspond to the high purity limestone with 53.15 ~ 55.64 wt. % CaO, and the light brown colored rocks contain 20.71 ~ 21.67 wt. % MgO. The bleaching of carbonate rocks are not related to CaO composition of the rocks, as light grey rocks tend to be higher in CaO content than those of the white rocks at the lower zone. The pelitic components are also occasionally increased in white limestone than light grey one. Al2O3 is one of the most difficult content to remove during hydrothermal processes, so the interpretation that the limestone is purified together with hydrothemral bleaching, has little merit. The wide range (over 16 ‰) of δ18OSMOW, smaller variation (within 2 ‰) of δ13CPDB are apparent in both the upper and lower zones, which indicate the Daegi Formation had been affected overall by hydrothermal fluids. The K-Ar isotopic age of hydrothermal alteration in the GMI limestone mine is 85.1 ± 1.7 Ma. Gradual change from grey through light grey to white limestone is accompanied by lower oxygen stable isotope values, which is major evidence that the hydrothermal effect is the main process of the bleaching. Although the Daegi Formation has suffered from hydrothermal activity and increase in whiteness, there is no clear evidence demonstrating the relationship between bleaching and high purity of limestone. The purification of limestone has nothing to do with the hydrothermal activity in this area. Instead, it should be considered that the change of sedimentary environment related to see-level fluctuation which can prevent deposition of pelitic components especially Al2O3 contrbuted to the formation of the high purity limestone in the upper zone of the Daegi Formation. Considering the evidences such as increase in CaO content of limestone by depth, gradual change from calcite to dolomite at the lower zones, and occurring the high purity limestone at the upper zone, the interpretation of sequence stratigraphic aspect to the formation of the high purity Daegi limestone appears to be more suitable than that of hydrothermal alteration origin.

Keywords Daegi Formation, high-purity limestone, Jeongseon, GMI mine, genetic environment

정선-삼척 일대 대기층 상부 고품위 석회석의 생성환경

김창성1* ·최선규1 ·김규보1 ·강정극1 ·김경배2 ·김학수3 ·이정상3 ·유인창4

1고려대학교 지구환경과학과, 2강원머티리얼, 3지오제니 컨설턴트, 4경북대학교 지구시스템과학부

Received: July 27, 2017; Revised: August 28, 2017; Accepted: August 30, 2017

요 약

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

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