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Origin of Fluorine Contained in Rocks within the Eulwangsan, Yongyudo
용유도 을왕산에 분포하는 암석 내 불소 기원
Econ. Environ. Geol. 2018 Dec;51(6):521-9
Published online December 31, 2018;  https://doi.org/10.9719/EEG.2018.51.6.521
Copyright © 2018 the Korean society of economic and environmental gelology.

Jong-Hwan Lee1, Jong-Ok Jeong2, Kun-Ki Kim3, Sang-Woo Lee1 and Soon-Oh Kim1*
이종환1 ·정종옥2 ·김건기3 ·이상우1 ·김순오1*

1Department of Geology and Research Institute of Natural Science (RINS), Gyeongsang National University(GNU), Jinju 52828, Republic of Korea
2Centralized Scientific Instrumentation Facility (CSIF), Gyeongsang National University(GNU), Jinju 52828, Republic of Korea
3Geochang Granite Research Center, Geochang 50103, Republic of Korea
1경상대학교 자연과학대학 지질과학과 및 기초과학연구소, 2경상대학교 공동실험실습관, 3(재)거창화강석연구센터
Received November 27, 2018; Revised December 7, 2018; Accepted December 15, 2018.
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 the original work is properly cited.
 Abstract
This study was conducted to investigate the natural origin of fluorine contained in the rocks within the Eulwangsan area via petrological and mineralogical analyses. The main geology of the Yongyudo Eulwangsan area is Triassic biotite granite. Biotite granite and mylonite are the major rock types containing fluorine at high levels (up to 1,700 and 2,400 mg/kg for biotite granite and mylonite, respectively). In the case of the biotite granite, a high concentration of fluorine can be contributed to fluorite, and the results of microscopic analyses show that the fluorite was observed as small veinlets filling cleavages and micro-fractures within alkali-feldspars and plagioclases, or observed together with quartz in ore veins, indicating the secondary formation of fluorite by hydrothermal fluids. In mylonite, on the other hand, a high fluorine concentration is attributable to sericite. Microscopic analyses revealed that the boundary between sericite and surrounding quartz was not clear, the sericite occurred filling the micro-fractures of quartz and encapsulating small quartz cataclasts. These results indicate that the sericite was also formed as a result of hydrothermal alteration. Consequently, it is speculated that the high fluorine level in the rocks of the Eulwangsan area of Yongyudo is of natural origin due to hydrothermal processes.
Keywords : Yongyudo Eulwangsan, fluorine, origin, fluorite, sericite

 

December 2018, 51 (6)