Journal of the Mineralogical Society of Korea (한국광물학회지)

The Mineralogical Society of Korea (한국광물학회)
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Illite, Reviewed on the Chemical Compositions - The Mixed Phase among Muscovite, Pyrophyllite and Chlorite: EPMA Quantitative Analysis of Shale from the Jigunsan Formation at Seokgaejae in Samchuk-City, Gangwon-do

화학조성으로 다시 보는 일라이트-백운모, 파이로필라이트 및 녹니석의 혼합상: 강원도 삼척시 석개재에 분포하는 직운산층 셰일에 대한 EPMA 정량분석

  • Choi, Seung-Hyun (Department of Earth and Environmental Sciences, Chonbuk National University) ;
  • Mun, Hyang-Ran (Department of Earth and Environmental Sciences, Chonbuk National University) ;
  • Lee, Young-Boo (Korea Basic Science Institute, Jeonju Center) ;
  • Lee, Jung-Hoo (Department of Earth and Environmental Sciences, Chonbuk National University)
  • 최승현 (전북대학교 지구환경과학과) ;
  • 문향란 (전북대학교 지구환경과학과) ;
  • 이영부 (한국기초과학지원연구원 전주센터) ;
  • 이정후 (전북대학교 지구환경과학과)
  • Received : 2012.09.04
  • Accepted : 2012.09.25
  • Published : 2012.09.28
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Abstract

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.

강원도 삼척시 석개재에서 산출되는 직운산층 셰일의 운모류 광물(일라이트)에 대한 EPMA 연구를 수행하였다. 정량분석으로 계산된 운모류 광물의 평균 화학식은 $(K_{1.17}Na_{0.04}Ca_{0.01})(Al_{2.80}Mg_{1.17}Fe_{0.78})(Si_{6.34}Al_{1.66})O_{20}(OH)_4$로, 소위 일라이트에 해당되는 화학조성을 보인다. 낮은 층간 양이온 값과 팔면체 자리의 높은 Mg, Fe값으로 보아 일라이트는 백운모, 파이로필라이트 및 녹니석의 혼합상으로 판단된다. 이 연구에서 분석된 일라이트에 해당되는 화학식을 각각의 구성광물로 분리하였고, 그 분리 방법을 새로이 고안하여 제시하였다. 일라이트의 화학식으로부터 K(Na, Ca 포함)를 기준으로 백운모의 함량을, Mg+Fe로부터 녹니석의 함량을 추산하고 나머지를 파이로필라이트로 간주하였다. 파이로필라이트는 이상화학식을, 녹니석은 평균 분석값을 사용하여 일라이트의 분석값에서 빼면, 나머지는 백운모의 화학식이 되는데 이는 원칙적으로 백운모의 이상화학식이 된다. 이 연구에서 분석한 운모류 광물의 평균 분석값을 이 방법으로 분리하면 백운모 61%, 녹니석 27.3%, 파이로필라이트 11.7%로 되며, 여기에서 계산된 백운모의 화학식은 $(K,Na,Ca)_{2.00}Al_{3.69}(Si_{6.75}Al_{1.25})O_{20}(OH)_4$이다. 이 백운모의 화학식은 대체로 낮은 Al값을 보이나 암석의 낮은 Al 함량과 녹니석 화학조성의 불확실성을 감안할 때 대체로 합리적인 것으로 간주되며, 이는 또한 이 연구에서 제시한 분리 방법이 합당하다는 것을 뒷받침한다.

Keywords

References

  1. Baek, J.H. (1994) A mineralogical study of layer silicates in the metamorphic rocks from the Southwestern part of the Ogcheon Metamorphic Belt. M.D. Thesis, Chonbuk National University, Jeonju (in Korean with English abstract).
  2. Choi, D.K., Chough, S.K., Kwon, Y.K., Lee, S.B., Woo, J., Kang, I., Lee, H.S., Lee, S.M., Shon, J.W., Shinn, Y.J., and Lee, D.J. (2004) Taebaek Group (Cambrian-Ordovician) in the Seokgaejae section, Taebaeksan Basin : a refined lower Paleozoic stratigraphy in Korea. Geosciences Journal, 8, 125-151. https://doi.org/10.1007/BF02910190
  3. Choi, S.H. (2009) A mineralogical study on the illite in the sedimentary rock from the Taebaek area : EPMA, TEM study. M.D. Thesis, Chonbuk National University, Jeonju (in Korean with English abstract).
  4. Choi, S.H., Lee, J.H., Lee, Y.B., Mun, H.R., and Choi, M.C. (2010) A study on the muscovite-pyrophyllite mixing from the EPMA analysis of illite. Proceedings of the Annual Joint Conference, Petrological Society of Korea and Mineralogical Society of Korea, Jeonju, Korea, May 27, 47-49.
  5. Choi, S.H., Mun, H.R., Lee, Y.B., and Lee, J.H. (2011) A study on the muscovite-pyrophyllite mixed phase in the shale from the Manhang formation, Taebaek area. J. Miner. Soc. Korea, 24, 313-320 (in Korean with English abstract). https://doi.org/10.9727/jmsk.2011.24.4.313
  6. Choi, S.H., Mun, H.R., Lee, Y.B., Lee, J.H., and Kim, Y.M. (2012) Mineralogical study on shales of the Sadong and Gobangsan formation, Munkyung area. J. Miner. Soc. Korea, 25, 1-8 (in Korean with English abstract). https://doi.org/10.9727/jmsk.2012.25.1.001
  7. Chough, S.K., Kwon, S.T., Ree, J.H., and Choi, D.K. (2000) Tectonic and Sedimentary evolution of the Korean peninsula : a review and new view. Earth Science Reviews, 52, 175-235. https://doi.org/10.1016/S0012-8252(00)00029-5
  8. Deer, W.A., Howie, R.A., and Zussman, J. (1992) An introduction to the rock forming minerals. 2nd edition. John Wiley and Sons, New York.
  9. Jiang, W.T., Essene, E.J., and Peacor, D.R. (1990) Transmission electron microscopic study of coexisting pyrophyllite and muscovite : Direct evidence for the metastability of illite. Clay. Clay Miner., 38, 225-240. https://doi.org/10.1346/CCMN.1990.0380301
  10. Lee, J.H. and Peacor, D.R. (1983) Intralayer transitions in phyllosilicates of the Martinsburg Shale. Nature, 303, 608-609. https://doi.org/10.1038/303608a0
  11. Lee, J.H., Peacor, D.R., Lewis, D.D., and Wintsch, R. P. (1984) Chlorite-illite/muscovite interlayered and interstratified crystals: A TEM/STEM study. Contrib. Mineral. Petr., 88, 372-385. https://doi.org/10.1007/BF00376762
  12. Lee, J.H. Ahn, J.H., and Peacor, D.R. (1985) Textures in layered silicates : progressive changes through diagenesis and low-temperature metamorphism. J. Sediment. Petrol., 55, 532-540.
  13. Lee, S.W. (1998) Mineralogical studies on the diagenesis of the shale in the Sindong group at the Kyongsang Basin : XRD, EPMA and TEM study. M.D. Thesis, Chonbuk National University, Jeonju (in Korean with English abstract).
  14. Lee, Y.B. (1993) Mineralogical studies of phyllosilicates on the diagenesis and metamorphism of the Jigunsan and the Manhang formation : EPMA/TEM study. M.D. Thesis, Chonbuk National University, Jeonju (in Korean with English abstract).
  15. Livi, K.T., Christidis, G.E., Árkai, P., and Veblen, D.R. (2008) White mica domain formation : A model for paragonite, margarite and muscovite formation during prograde metamorphism. Am. Mineral., 93, 520-527. https://doi.org/10.2138/am.2008.2662
  16. Srodon, J. and Eberl, D.D. (1984) Illite. In: Bailey, S.W. (ed.) Micas, Reviews in Mineralogy, Vol. 13, Mineral. Soc. America, 495-544.
  17. Woo, J. and Chough, S.K. (2007) Depositional process and sequence stratigraphy of the Jigunsan Formation (Middle Ordovician), Taebaeksan Basin, mideast Korea : implications for basin geometry and sequence development. Geosciences Journal, 11, 331-355. https://doi.org/10.1007/BF02857050

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