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标题：Characteristics of Cordierite (Iolite) of Bandarguha-Orabahala Area, Kalahandi District, Odisha, India
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作者：Das SK ; Mohanty JK
期刊名称：Journal of Geology & Geophysics
电子版ISSN：2381-8719
出版年度：2017
卷号：6
期号：4
页码：1-8
DOI：10.4172/2381-8719.1000294
语种：English
出版社：OMICS International
摘要：Optical microscopy, X-ray diffractometry, micro CT studies and mineral chemistry by SEM-EDS has been carried out on cordierite rich rock fragments from Bandarguha and Orabahala areas of Kalahandi district, Odisha. Macroscopically, cordierite grains exhibit distinct pleochroism in the shades of violet blue to light blue and colourless and are of gem quality (iolite). Biotite is the dominant associated mineral and Mg-Fe distribution coefficient (KD) between coexisting cordierite and biotite varies from 1.71 to 2.76. The cordierite is low cordierite (distortion index, Δ=0.257). Mineral analyses indicate that cordierite is magnesian rich (XMg=0.82-0.88) with limited Fe2+ substitution for Mg2+ and dichroism is due to presence of part of iron in ferric form. Cordierite is formed during metamorphism by reactions: (a) orthopyrox ene+sillimanite+quartz=cordierite+K-feldspar+water and (b) orthopyroxene+sillimanite=cordierite+corundum.
关键词：Cordierite; Pleochroism; Pinitisation; Distortion index; Mg-Fe exchange; Odisha