2014; 47(4): 317-333

Published online August 31, 2014

https://doi.org/10.9719/EEG.2014.47.4.317

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

Geology, Mineralization, and Age of the Pocheon Fe(-Cu) Skarn Deposit, Korea

Chang Seong Kim1, Ji Su Go1, Seon-Gyu Choi1* and Sang-Tae Kim2

1Dept. of Earth & Environmental Sciences, Korea University, Seoul 136-713, Korea
2School of Geography and Earth Sciences, McMaster University, Ontario L8S4L8, Canada

Correspondence to :

 

Received: April 15, 2014; Revised: May 7, 2014; Accepted: May 8, 2014

Abstract

The Pocheon iron (-copper) deposit, located at the northwestern part of the Precambrian Gyeonggi massif in South Korea, genetically remains controversial. Previous researchers advocated a metamorphosed (-exhalative) sedimentary origin for iron enrichment. In this study, we present strong evidences for skarnification and Fe mineralization, spatially associated with the Myeongseongsan granite. The Pocheon deposit is composed of diverse carbonate rocks such as dolostone and limestone which are partially overprinted by various hydrothermal skarns such as sodic-calcic, calcic and magnesian skarn. Iron (-copper) mineralization occurs mainly in the sodic-calcic skarn zone, locally superimposed by copper mineralization during retrograde stage of skarn. Age data determined on phlogopites from retrograde skarn stage by Ar-Ar and K-Ar methods range from 110.3±1.0 Ma to 108.3±2.8 Ma, showing that skarn iron mineralization in the Pocheon is closely related to the shallow-depth Myeongseongsan granite (ca. 112 Ma). Carbon-oxygen isotopic depletions of carbonates in marbles, diverse skarns, and veins can be explained by decarbonation and interaction with an infiltrating hydrothermal fluids in open system (XCO2=0.1). The results of sulfur isotope analyses indicate that both of sulfide (chalcopyrite-pyrite composite) and anhydrites in skarn have very high sulfur isotope values, suggesting the 34S enrichment of the Pocheon sulfide and sulfate sulfur was derived from sulfate in the carbonate protolith. Shear zones with fractures in the Pocheon area channeled the saline, high fO2 hydrothermal fluids, resulting in locally developed intense skarn alteration at temperature range of about 500° to 400°C.

Keywords Pocheon, mineralization age, iron mineralization, sodic-calcic skarn, stable isotope

Article

2014; 47(4): 317-333

Published online August 31, 2014 https://doi.org/10.9719/EEG.2014.47.4.317

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

Geology, Mineralization, and Age of the Pocheon Fe(-Cu) Skarn Deposit, Korea

Chang Seong Kim1, Ji Su Go1, Seon-Gyu Choi1* and Sang-Tae Kim2

1Dept. of Earth & Environmental Sciences, Korea University, Seoul 136-713, Korea
2School of Geography and Earth Sciences, McMaster University, Ontario L8S4L8, Canada

Correspondence to:

 

Received: April 15, 2014; Revised: May 7, 2014; Accepted: May 8, 2014

Abstract

The Pocheon iron (-copper) deposit, located at the northwestern part of the Precambrian Gyeonggi massif in South Korea, genetically remains controversial. Previous researchers advocated a metamorphosed (-exhalative) sedimentary origin for iron enrichment. In this study, we present strong evidences for skarnification and Fe mineralization, spatially associated with the Myeongseongsan granite. The Pocheon deposit is composed of diverse carbonate rocks such as dolostone and limestone which are partially overprinted by various hydrothermal skarns such as sodic-calcic, calcic and magnesian skarn. Iron (-copper) mineralization occurs mainly in the sodic-calcic skarn zone, locally superimposed by copper mineralization during retrograde stage of skarn. Age data determined on phlogopites from retrograde skarn stage by Ar-Ar and K-Ar methods range from 110.3±1.0 Ma to 108.3±2.8 Ma, showing that skarn iron mineralization in the Pocheon is closely related to the shallow-depth Myeongseongsan granite (ca. 112 Ma). Carbon-oxygen isotopic depletions of carbonates in marbles, diverse skarns, and veins can be explained by decarbonation and interaction with an infiltrating hydrothermal fluids in open system (XCO2=0.1). The results of sulfur isotope analyses indicate that both of sulfide (chalcopyrite-pyrite composite) and anhydrites in skarn have very high sulfur isotope values, suggesting the 34S enrichment of the Pocheon sulfide and sulfate sulfur was derived from sulfate in the carbonate protolith. Shear zones with fractures in the Pocheon area channeled the saline, high fO2 hydrothermal fluids, resulting in locally developed intense skarn alteration at temperature range of about 500° to 400°C.

Keywords Pocheon, mineralization age, iron mineralization, sodic-calcic skarn, stable isotope

    KSEEG
    Dec 29, 2023 Vol.56 No.6, pp. 629~909

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