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Electron-optical studies of phyllosilicate intergrowths in sedimentary and metamorphic rocks

Published online by Cambridge University Press:  05 July 2018

S. H. White ,
J. M. Huggett  and
H. F. Shaw
S. H. White
Affiliation:
Department of Geology, Imperial College, London SW7, UK
J. M. Huggett
Affiliation:
Department of Geology, Imperial College, London SW7, UK
H. F. Shaw
Affiliation:
Department of Geology, Imperial College, London SW7, UK
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Abstract

The results of a microstructural study by backscattered scanning electron microscopy and a microchemical study using X-ray microprobe analysis of phyllosilicate intergrowths from sandstones, shales, metagreywackes, and low-grade schists are presented. The microstructural study revealed that the intergrowths thicken and become more coherent with metamorphic grade; the intergrowths change from incoherent to coherent in the anchizone. The increasing coherency is mirrored by an increase in the crystallinity indices of the illites/phengites. Chemical analysis of the individual intergrowth phases was difficult in the sediments and no systematic compositional variations were recorded. However, clear compositional trends with increasing metamorphic grade emerged in the phengites from the metagreywackes and schists, but in the chlorites only slight compositional changes were recorded.

Keywords

electron microscopyelectron microprobe analysisphyllosilicatesillitephengitesedimentary rocksmetamorphic rocks
Type
Research Article
Information
Mineralogical Magazine , Volume 49 , Issue 352 , June 1985 , pp. 413 - 423
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1985

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Footnotes

*

Present address: BP Petroleum Development Limited, Britannic House, London EC2, UK.

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