• Korean Journal of Heritage: History & Science
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• v.50 no.3
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• pp.126-145
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• 2017

The Seokgaejae section is located along a timber access road and a driveway across Bonghwa County, North Gyeongsang Province, and Samcheog city, Gangwon Province. Its stratigraphic column shows all of the ten strata of the lower Paleozoic Taebaek Group, Joseon Supergroup. The Seokgaejae section is proved to be scientifically important. Thirty-eight domestic/international journal papers have been published on this early Paleozoic stratigraphic site, and many distinguished researchers over the world have visited the site. However, the section has never been considered to be designated as a national natural monument and was not included in the adjacent Gangwon Paleozoic National Geopark due to management or administrative issues. Although the Seokgaejae section sufficiently satisfies many of the national natural monument criteria, designation for the natural monument may not be justified because of the facts that the outcrop was artificially exposed by road construction; the chance of destruction of the outcrop is relatively few; demage on the outcrop to some extent does not impair the intrinsic value of the section; and the geomorphological/landscape value of the section is low. The application of the recently modified geological heritage assessment model to the Seokgaejae section shows very high scores on the scientific/educational, intrinsic, and functional values. Based on the improved geological heritage grade standard, the Seokgaejae section conforms to the national-level protection criteria. It is strongly recommended to manage the Seokgaejae section as a principal geosite by including it in the Gangwon Paleozoic National Geopark. This case study on the Seokgaejae section also suggests that the process of application and endorsement of a national geopark need further improvement. As well as the improvement of the system or policy related to geological heritages, further efforts of the experts in various fields of geoscience are required in order for other geological heritages not to be neglected from now on.

• Journal of the Mineralogical Society of Korea
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• v.25 no.3
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• pp.143-153
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• 2012

Mica-type minerals (illites) in the shales of the Jigunsan formation at Seokgaejae in Samchuk-City, Gangwon-do are studied using electron probe micro analysis (EPMA). The average chemical formula of the mica-type mineral obtained from the quantitative analysis is $(K_{1.17}Na_{0.04}Ca_{0.01})(Al_{2.80}Mg_{1.17}Fe_{0.78})(Si_{6.34}Al_{1.66})O_{20}(OH)_4$, which shows a chemical formula within the range of illite. These illites so called can be considered as mixed-phases among muscovite, pyrophyllite and chlorite due to the low contents of interlayer cations and high Mg, Fe. The formula of illite is separated into those three minerals and the method for the separation is newly formulated and proposed in this study. From the formula of illite, the content of muscovite is estimated from K (Na and Ca included), the content of chlorite by Mg+Fe, and the rest remains as pyrophyllite. The chemical formula of muscovite can be calculated by subtracting the compositions of pyrophyllite and chlorite from the analyzed composition of illite using an ideal formula for pyrophyllite and analyzed average formula for chlorite. The calculated formula of muscovite is supposed to be stoichiometric in principle. The result of the separation of analyzed illite is 61% muscovite, 27.3% chlorite and 11.7% pyrophyllite and the calculated formula of muscovite after separation is $(K,Na,Ca)_{2.00}Al_{3.69}(Si_{6.75}Al_{1.25})O_{20}(OH)_4$. The calculated formula of muscovite slightly low in Al content can be considered to be reasonable in general when the low content of Al in the rock and the uncertainties of chlorite compositions used in the calculation are counted. This supports that the method of separation proposed in this study is also applicable.

• Economic and Environmental Geology
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• v.51 no.4
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• pp.323-343
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• 2018

This study defines the mineralogical, micro-textural and geochemical characteristics for the carbonate rocks and discusses the fluids that have affected the depositional environment of the Lower Makgol Formation in Seokgaejae section. Based on analysis of X-ray Diffraction (XRD), Scanning Electron Microscope-Energy Dispersive X-ray Spectrometry (SEM-EDS), Electron Probe Micro Analyzer-Wavelength Dispersive X-ray Spectrometry (EPMA-WDS) and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS), carbonate miorofacies in the basal and the lower members of the Makgol Formation are distinguished and classified into four types. Type 1 dolomite (xenotopic interlocking texture) and Type 2 dolomite (idiotopic interlocking texture) have relatively high Mg/Ca ratio, flat REE pattern, low Fe and Mn. Extensively interlocking textures in these dolomites indicate constant supply of Mg ion from hypersaline brine. Type 3 and Type 4 dolomite (scattered and loosely-aggregated texture) have relatively moderate Mg/Ca ratio, MREE enriched pattern, low to high Fe and Mn. These partial dolomitization indicate limited supply of Mg ion under the influx of meteoric water with seawater. Also, the evidence of Fe-bearing minerals, recrystallization and relatively high Fe and Mn in Type 4 indicates the influence of secondary diagenetic fluids under suboxic conditions. Integrating geochemical data with mineralogical and micro-textural evidence, the discrepancy between the basal and the lower members of the Makgol Formation indicates different sedimentary environment. It suggest that hypersaline brine have an influence on the basal member, while mixing meteoric water with seawater have an effect on the lower member of the Makgol Formation.