Effective crustal permeability controls fault evolution: An integrated structural, mineralogical and isotopic study in granitic gneiss, Monte Rosa, Northern Italy

Lawther, S. E.M., Dempster, T. J. , Shipton, Z. K. and Boyce, A. J. (2016) Effective crustal permeability controls fault evolution: An integrated structural, mineralogical and isotopic study in granitic gneiss, Monte Rosa, Northern Italy. Tectonophysics, 690(A), pp. 160-173. (doi: 10.1016/j.tecto.2016.07.010)

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Abstract

Two dextral faults within granitic gneiss in the Monte Rosa nappe, northern Italy reveal key differences in their evolution controlled by evolving permeability and water/rock reactions. The comparison reveals that identical host rock lithologies develop radically different mineralogies within the fault zones, resulting in fundamentally different deformation histories. Oxygen and hydrogen isotope analyses coupled to microstructural characterisation show that infiltration of meteoric water occurred into both fault zones. The smaller Virgin Fault shows evidence of periodic closed system behaviour, which promoted the growth of hydrothermal K-feldspar, whilst the more open system behaviour of the adjacent Ciao Ciao Fault generated a weaker muscovite-rich fault core, which promoted a step change in fault evolution. Effective crustal permeability is a vital control on fault evolution and, coupled to the temperature (i.e. depth) at which key mineral transformations occur, is probably a more significant factor than host rock strength in controlling fault development. The study suggests that whether a fault in granitic basement grows into a large structure may be largely controlled by the initial hydrological properties of the host rocks. Small faults exposed at the surface may therefore be evolutionary “dead-ends” that typically do not represent the early stages in the development of larger faults.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Boyce, Professor Adrian and Dempster, Dr Tim and Shipton, Dr Zoe
Authors: Lawther, S. E.M., Dempster, T. J., Shipton, Z. K., and Boyce, A. J.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
University Centres > Centre for Internationalisation and Enterprise Research
Journal Name:Tectonophysics
Publisher:Elsevier
ISSN:0040-1951
ISSN (Online):1879-3266
Published Online:18 July 2016
Copyright Holders:Copyright © 2016 The Authors
First Published:First published in Tectonophysics 690(A): 160-173
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
470531Fluid flow through fault zones in granite exhumed from seismogenic depthsZoe ShiptonNatural Environment Research Council (NERC)NE/F007671/1SCHOOL OF GEOGRAPHICAL & EARTH SCIENCES