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Finite strain has no influence on the illite crystallinity of tectonized Eocene limestone breccias of the Morcles nappe, Swiss Alps

Published online by Cambridge University Press:  09 July 2018

M. Burkhard  and
N. Badertscher
M. Burkhard*
Affiliation:
Institut de Géologie, Université de Neuchâtel, rue E. Argand 11, CH 2007 Neuchâtel, Switzerland
N. Badertscher
Affiliation:
Institut de Géologie, Université de Neuchâtel, rue E. Argand 11, CH 2007 Neuchâtel, Switzerland
*
*E-mail: [email protected]
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Abstract

The relationship between illite crystallinity (IC) and finite strain as well as lattice strain and crystallite size of illite is examined in a series of 27 deformed breccia samples from the inverted limb of the Morcles nappe. The IC is determined independently for limestone components and a red/green clay-silt matrix. The finite strain varies widely (D= 0.8–2.5). The IC values vary from diagenetic to epizonal, but no correlation with finite strain could be established. The spread of IC values is explained by heterogeneities within the protolith which have not been homogenized/ obliterated by the anchizonal to epizonal metamorphic overprint. While limestone pebbles display IC values in agreement with the regional metamorphic conditions, the clay-silt matrix has anomalously high IC values, even after deconvolution of the 10 Å peak to correct for the presence of paragonite/muscovite. No correlation could be established between finite strain, lattice strain and/or crystallite size of illite.

Keywords

finite strainillite crystallinitylimestone brecciasMorcles nappeSwitzerland
Type
Research Article
Information
Clay Minerals , Volume 36 , Issue 2 , June 2001 , pp. 171 - 180
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2001

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