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The microstructural and rheological evolution of shear zones

By
Nicholas J. Austin
Nicholas J. Austin
Department of Earth Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USAPresent address: Imperial Oil Resources, 237 4th Ave SW, Calgary, Alberta, Canada (e-mail: nicholas.j.austin@esso.ca)
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Published:
January 01, 2011

Abstract

Evidence of localized strain is ubiquitous in deformed lithospheric rocks. Recent advances in laboratory deformation techniques, including the use of torsion experiments, have enabled the coupling of microstructural and rheological evolution to be investigated in experiments run to strains approaching those reached in many natural shear zones. Further, the increased use of electron backscatter diffraction to quantify crystallographic preferred orientation (CPO) has significantly increased understanding of CPO formation and evolution. Combined, these laboratory and field observations support the assertion that a rock's microstructure is strongly linked to its rheology. However, complete quantification of the coupling between microstructure and rheology is complicated by the fact that rocks have inherently complex microstructures. This paper reviews recent work focused on quantifying the rates of microstructural evolution and the attainment of steady state for two key microstructural parameters: grain size and crystallographic preferred orientation. Theoretical considerations, laboratory measurements and field observations suggest that a full description of all relevant microstructural parameters, and the appropriate evolution equations for these parameters, may be needed to link microstructural and rheological evolution and therefore to quantify the bulk rheology of the lithosphere.

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Contents

Geological Society, London, Special Publications

Deformation Mechanisms, Rheology and Tectonics: Microstructures, Mechanics and Anisotropy

David J. Prior
David J. Prior
University of Otago, New Zealand
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Ernest H. Rutter
Ernest H. Rutter
University of Manchester, UK
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Daniel J. Tatham
Daniel J. Tatham
University of Liverpool, UK
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Geological Society of London
Volume
360
ISBN electronic:
9781862394483
Publication date:
January 01, 2011

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