Granular flow in polymineralic rocks bearing sheet silicates: New evidence from natural examples

Herwegh, Marco; Jenni, Andreas (2001). Granular flow in polymineralic rocks bearing sheet silicates: New evidence from natural examples. Tectonophysics, 332(3), pp. 309-320. Elsevier

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Natural deformation in carbonate mylonites bearing sheet silicates occurs via a complex interaction of granular flow and solution transfer processes and involves continuous cycles of dissolution, grain boundary diffusion, nucleation and growth. In this way, new sheet silicates (a) nucleate within voids formed by grain boundary sliding of calcite grains. (b) grow, and (c) rotate towards the shear plane. As a consequence, small mica grains show a wide range of orientations with respect to the shear plane, but moderate to large grains are subparallel both to each other and to the shear plane. Increases of average grain sizes with increasing temperature of sheet silicates in mica-rich layers is more pronounced than in mica-poor layers. In the calcitic matrix however, sheet silicates can only grow via solution-precipitation and mass transfer processes. Therefore, the observed grain size variability indicates drastic differences in mass transfer behavior between the individual layers, which might be related to differences in the fluid flux. Based on these observations, a conceptual model for the microfabric evolution in sheet silicate bearing mylonites is presented. © 2001 Elsevier Science B.V. All rights reserved.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Tectonics

UniBE Contributor:

Herwegh, Marco and Jenni, Andreas

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0040-1951

Publisher:

Elsevier

Language:

English

Submitter:

Andreas Jenni

Date Deposited:

23 Oct 2015 14:37

Last Modified:

25 Jul 2016 14:49

Uncontrolled Keywords:

Calcite, Deformation mechanism polymineralic rock, Helvetics Sheet silicate, deformation mechanism, mica, mylonite, silicate, texture

BORIS DOI:

10.7892/boris.72228

URI:

https://boris.unibe.ch/id/eprint/72228

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