Wallis, D, Lloyd, GE orcid.org/0000-0002-7859-2486, Phillips, RJ et al. (2 more authors) (2015) Low effective fault strength due to frictional-viscous flow in phyllonites, Karakoram Fault Zone, NW India. Journal of Structural Geology, 77. pp. 45-61. ISSN 0191-8141
Abstract
Phyllosilicate-rich fault rocks are common in large-scale fault zones and can dramatically impact fault rheology. Experimental evidence suggests that multi-mechanism frictional-viscous flow (FVF) may
operate in such lithologies, potentially significantly weakening mature fault cores. We report microstructures indicative of FVF in exhumed phyllonites of the Karakoram Fault Zone (KFZ), NW India. These
include interconnected muscovite foliae, lack of quartz/feldspar crystal preferred orientations, and sutured grains and overgrowths indicative of fluid-assisted diffusive mass transfer. FVF microphysical modelling, using microstructural observations from the natural fault rock and experimentally-derived friction and diffusion coefficients, predicts low peak shear strengths of <20 MPa within the frictional viscous transition zone. Chlorite geothermometry indicates that synkinematic chlorites grew at 351 ± 34 C (c. 10 km depth) during FVF, immediately above the transition to quartz crystal plasticity. The deformation processes and interpreted low shear strength of the exhumed KFZ fault rocks provide analogues for processes operating currently at depth in active faults of similar scale. If similar lithologies are present at depth, then the Quaternary seismic characteristics of the KFZ support faults with phyllonitic cores being able to accommodate large seismic ruptures. The results also provide rare rheological constraints for mechanical models of the India-Asia collision zone.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). |
Keywords: | Karakoram Fault Zone; Fault weakening; Frictional-viscous flow; Phyllonite; Deformation-fluid-metamorphism; interactions; Shear strength |
Dates: |
|
Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 04 Jun 2015 14:08 |
Last Modified: | 29 Oct 2020 16:46 |
Published Version: | http://dx.doi.org/10.1016/j.jsg.2015.05.010 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.jsg.2015.05.010 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:86669 |