Rheology of naturally deformed antigorite serpentinite: strain and strain‐rate dependence at mantle‐wedge conditions

Tulley, C. J., Fagereng, Å. ORCID: https://orcid.org/0000-0001-6335-8534, Ujiie, K., Piazolo, S., Tarling, M. S. and Mori, Y. 2022. Rheology of naturally deformed antigorite serpentinite: strain and strain‐rate dependence at mantle‐wedge conditions. Geophysical Research Letters 49 (16) , e2022GL098945. 10.1029/2022gl098945

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Abstract

Antigorite serpentinite is expected to occur in parts of subduction plate boundaries, and may suppress earthquake slip, but the dominant deformation mechanisms and resultant rheology of antigorite are unclear. An exhumed plate boundary shear zone exposed near Nagasaki, Japan, contains antigorite deformed at 474°C ± 30°C. Observations indicate that a foliation defined by (001) crystal facets developed during plate‐boundary shear. Microstructures indicating grain‐scale dissolution at high‐stress interfaces and precipitation in low‐stress regions suggest that dissolution‐precipitation creep contributed to foliation development. Analysis of crystal orientations indicate a small contribution from dislocation activity. We suggest a frictional‐viscous rheology for antigorite, where dissolution‐precipitation produces a foliation defined by (001) crystal facets and acts to resolve strain incompatibilities, allowing for efficient face‐to‐face sliding between facets. This rheology can not only explain aseismic behavior at ambient plate boundary conditions, but also some of the contrasting behaviors shown by previous field and laboratory studies.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Additional Information:	License information from Publisher: LICENSE 1: URL: http://creativecommons.org/licenses/by/4.0/
Publisher:	Wiley
ISSN:	0094-8276
Date of First Compliant Deposit:	30 August 2022
Date of Acceptance:	17 August 2022
Last Modified:	10 Jun 2023 22:17
URI:	https://orca.cardiff.ac.uk/id/eprint/152200

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