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Licensed Unlicensed Requires Authentication Published by De Gruyter (O) January 26, 2019

Identification of twins in muscovite: an electron backscattered diffraction study

  • Shan-Rong Zhao EMAIL logo , Chang Xu and Chuan Li

Abstract

Twins in micas are difficultly identified due to mica’s hexagonal pseudosymmetry. Many theoretic studies on mica twins have been reported but experimental observations are very limited. In this paper, we present an electron backscattered diffraction analysis to identify twins in the muscovite in a quartz schist occurring in the UHP-HP metamorphic rock belt in Dabie Mountain, China. A trilling twin with twin law <310>/{110} is common in the muscovite. A six-couplet twin consisting of two trilling twins related by twin laws <110>/{130} and <001>/{001}(or <100>/{100}) has been discovered. This six-couplet twin contains many cross-twin relationships among the most common mica twin laws <310>/{110}, <110>/{130} and <001>/{001}. The composition plane for twin laws <110>/{130} and <001>/{001} is {001} which is reasonable in mica structure to form a twin by rotation around twin axes, and that for twin law <310>/{110} is irregular based on EBSD resolution. A possible misindexation of a trilling twin or a 3T polytype during EBSD test is discussed, which is helpful to distinguish a twin from a polytype in micas. The occurring frequency of twin law <310>/{110} is higher than that of twin laws <110>/{130} and <001>/{001}, which is consistent to the deducing result from mica structure analysis. This research provides a convenient and effective EBSD method to identify mica twins and an experimental method to distinguish a twin from a polytype in micas, which is a problem confusing researchers for many years.

Acknowledgements

We are grateful to Dr Hai-Jun Xu and Da-Peng Wen for the kindly help on EBSD testing. We acknowledge financial support from National Nature Science Fundation of China (41372058, 41872037). The EBSD was performed in State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences.

References

[1] G. Donnay, N. Morimoto, Trioctahedral one-layer micas. I. Crystal structure of a synthetic iron mica. Acta Crystallogr.1964, 17, 1369.10.1107/S0365110X64003450Search in Google Scholar

[2] M. Nespolo, H. Takeda, G. Ferrais, T. Kogure, Composite twins of 1M mica: derivation and identification. Mineral. J.1997, 19, 173.10.2465/minerj.19.173Search in Google Scholar

[3] M. Nespolo, G. Ferrais, H. Takeda, Twins and allotwins of basic mica polytypes: theoretical derivation and identification in the reciprocal space. Acta Crystallogr. A2000, 56, 132.10.1107/S0108767399014907Search in Google Scholar PubMed

[4] M. Rieder, Lithium-iron micas from the Krusnehory Mountains (Erzgebirge): twins, epitactic overgrowths and polytypes. Z. Kristallogr.1970, 132, 161.10.1524/zkri.1970.132.1-6.161Search in Google Scholar

[5] R. Sadanaga, Y. Takfiuchi, Polysynthetic twinning of micas. Z. Kristallogr.1961, 116, 406.10.1524/zkri.1961.116.3-6.406Search in Google Scholar

[6] M. Nespolo, G. Ferrais, H. Takeda, Identification of two allotwins of mica polytypes in reciprocal space through the minimal rhombus unit. Acta Crystallogr. B2000, 56, 639.10.1107/S0108768100002044Search in Google Scholar

[7] L. Menegon, S. Piazolo, G. Pennacchioni, The effect of Dauphiné twinning on plastic strain in quartz. Contrib Mineral Petrol2011, 161, 635.10.1007/s00410-010-0554-7Search in Google Scholar

[8] S. R. Zhao, H. J. Xu, Q. Y. Wang, K. G. Yang, Electron backscatter diffraction study on twins and intergrowths among quartz crystals in granite. J. Appl. Crystallogr.2013, 46, 1414.10.1107/S0021889813017913Search in Google Scholar

[9] C. F. Ávila, L. Lagoeiro, P. F. Barbosa, L. Graca, EBSD analysis of rhombohedral twinning in hematite crystals of naturally deformed iron formation. J. Appl. Crystallogr.2015, 48, 212.10.1107/S1600576714025928Search in Google Scholar

[10] C. R. Brugger, J. E. Hammer, Prevalence of growth twins among anhedral plagioclase micrilites. Am. Mineral.2015, 100, 385.10.2138/am-2015-4809Search in Google Scholar

[11] C. Xu, S. R. Zhao, C. Li, X. He, Plagioclase twins in basalt – an electron backscatter diffraction study. J. Appl. Crystallogr.2016, 49, 2145.10.1107/S1600576716015739Search in Google Scholar

[12] X. C. Liu, S. Z. Li, B. M. Jahn, Tectonic evolution of the Tongbai-Hong’an orogen in central China: From oceanic subduction/accretion to continent-continent conllision. Science China-Earth Sciences2015, 58, 1477 (in Chinese).10.1007/s11430-015-5145-zSearch in Google Scholar

[13] R. X. Zhang, S. Y. Yang, A mathematical model for determining carbon coating thickness and its application in electron probe microanalysis. Microsc. Microanal.2016, 22, 1374.10.1017/S143192761601182XSearch in Google Scholar

[14] E. W. Radoslovich, The structure of muscovite, KAl2(Si3Al)O10(OH)2. Acta Crystallogr.1960, 13, 919.10.1107/S0365110X60002259Search in Google Scholar

[15] A. Amisano-Canesi, G. Chiari, G. Ferraris, G. Ivaldi, S. V. Soboleva, Muscovite- and phengite-3T: crystal structure and conditions of formation. Eur. J. Mineral.1994, 6, 489.10.1127/ejm/6/4/0489Search in Google Scholar

[16] D. J. Prior, J. Wheeler, L. Peruzzo, R. Spiess, C. Storey, Some garnetmicrostructures: an illustration of the potential of orientation maps and misorientation analysis in microstructural studies. J. Struct. Geol.2002, 24, 999.10.1016/S0191-8141(01)00087-6Search in Google Scholar

[17] G. W. Brindley, G. Brown, Crystal Structures of Clay Minerals and their X-ray Identification, Mineralogical Society Monograph No. 5, Mineralogical Society, London, 1980.10.1180/mono-5Search in Google Scholar

[18] M. E. Fleet, Micas, Rock-Forming Minerals, Second edition, Volume 3A, (Ed. H. Deer, and Zussman) The Geological Society, London, 2003.Search in Google Scholar

Received: 2018-10-13
Accepted: 2018-12-13
Published Online: 2019-01-26
Published in Print: 2019-05-27

©2019 Walter de Gruyter GmbH, Berlin/Boston

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