• Journal of the Mineralogical Society of Korea
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• v.8 no.1
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• pp.1-12
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• 1995

옥천 변성대 남서부 지역에서 산출되는 변성 니질암에서는 muscovite, biotite 및 chlorite를 주로하는 phyllosilicate가 서로 intergrowth 또는 interlayer를 이루는 것이 편광현미경 관찰, EPMA 분석, Back Scattered Electron (BSE) image 관찰 및 Transmission Electron Micro-scope(TEM) 관찰을 통하여 확인되었다. 이들 광물들은 편광현미경 관찰에서 흔히 각각의 입자를 식별할 수 없을 정도의 미세 규모로 서로 intergrow 되어 있으며BSE image에서는 0.1$\mu\textrm{m}$ 이하의 아주 작은 크기에서부터 10.0$\mu\textrm{m}$ 정도 크기까지 다양한 규모의 intergrow를 형성하고 있음이 관찰되었다. TEM scale에서는 개별 layer 크기(약 10$\AA$)에서부터 수십 개 layer 크기의 interlayering을 보여준다. 이와 같은 intergrowth 또는 interlayering의 결과로 EPMA 분석에서 종종 보기에는 규진(homogeneous)한 입자라 하더라도 두 개 이상의 광물 성분이 섞여 있는 분석값을 나타내며 이러한 nonstoichiometry는 BSE image에서 interlayer(또는 intergrow) 된 것으로 관찰되는 부분에서 더욱 두드러진다.Chlorite zone에서는 chlorite와 muscovite의 interlayering (C/M)이 주로 발견되며 biotite zone과 garnet zone에서는 chlorite와 biotite의 interlayer (C/B)가 주로 관찰된다. 이는 chlorite zone에서는 속성작용에서 보편적으로 나타나는 C/M으로부터 chlorite가 분리되는 광물반응이 일어나는데 반해서 biotite zone과 garnet zone에서는 chlorite로부터 C/B를 거쳐 biotite를 생성하는 광물반응이 일어나는 것을 의미한다. 이와 같은 현상은 변성작용에서 phollosilicate의 광물반응의 엄밀한 의미에서는 평형(equilibrium) 상태에서 균질한 광물을 생성하기보다는 비평형(disequilibrium) 반응으로 일어난다는 것을 의미한다.

• Journal of the Mineralogical Society of Korea
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• v.15 no.2
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• pp.122-131
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• 2002

Muscovite, chlorite and biotite in metapelites of the Ogcheon Hetamorphic Belt are studied using electron probe microanalysis (EPMA), backscattered electron images (BEI) of scanning electron microscopy (SEM) and lattice fringe images of transmission electron microscopy (TEM). These minerals are observed to be intergrown under a polarized light microscope and are apparently interlayered below EPMA resolution; EPMA data often indicate mixtures of phyllosilicates such as muscovite/chlorite (M/C), biotite/chlorite (B/C), muscovite/pyrophyllite/chlorite (M/P/C). biotite/pyrophyllite/chlorite (B/P/C) or biotite/muscovite/chlorite (B/M/C). BEI observations show that the three minerals (muscovite, chlorite and biotite) are mixed at various scales in a grain through the garnet zone, and the interlayering of the three minerals are observed from TEM lattice fringe images and selected area electron diffraction patterns. The result of TEM observations reveals that 7-$\AA$ layers (serpentine, precursor of chlorite) are interlayered within 10-$\AA$ layers (muscovite) at 100~200 $\AA$ scale as well as M/C in the chlorite zone. The 7-$\AA$ layers become smaller in size and less frequent in the biotite tone, and 10-$\AA$ layers are interlayered with chlorite (14 $\AA$) at an individual layer scale. The 7-$\AA$ layers are no longer observed in the garnet zone, and 10-$\AA$ layers (biotite) are interlayered with chlorite (B/C) at 50~100 $\AA$ scale. Relatively large scale (1000~2000 $\AA$) of intergrowth is also frequently observed from the garnet zone samples. However, rocks from all three metamorphic zones show interlayering of a few units of 7-, 10- and 14-$\AA$ layers with each other at TEM observations. The result of this study implies that metamorphic minerals such as muscovite, chlorite and biotite form through disequilibrum mineral reactions resulting in inhomogenious phases.

• Journal of the Mineralogical Society of Korea
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• v.17 no.3
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• pp.221-233
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• 2004

Mineralogical characteristics and genesis of phlogopite in the talc deposits of the chungnam area were studied. Mica is one of the major impurity of talc ores in the study area. Talc-related micas show typical phlogopite composition, whereas talc-unrelated micas show wide compositional variations between biotite and phlogopite. Phlogopite mainly occurs in the black-wall type zone, especially in the nodular talc ores near the outer part of talc ore bodies. Interleaving textures of phlogopite and chlorite are easily observed under the optical microscope and back-scattered electron images. Interleaving textures of phlogopite and talc are observed also. Examination of the phlogopite by transmission electron microscope reveals that 14 $\AA$ layers of chlorite are randomly interlayered within the 10 $\AA$ layers of phlogopite, which suggests that the genesis of phlogopite is closely related to chlorite. Considering the occurrence and mineralogical characteristics of phlogopite, and the possible origin of K for the formation of phlogopite, phlogopite of the study area was formed by interaction between talc ore body and hydrothermal solution containing sufficient K at the late stage of talc formation. K might be introduced from the granitic gneiss at the contact zone between the talc ore body and the granitic gneiss under favorable structural condition for the potash metasomatism.