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Fluid-related deformation processes at the up- and downdip limits of the subduction thrust seismogenic zone: What do the rocks tell us?

Fagereng, Ake, Diener, Johann F.A., Ellis, Susan and Remitti, Francesca 2018. Fluid-related deformation processes at the up- and downdip limits of the subduction thrust seismogenic zone: What do the rocks tell us? In: Byrne, Timothy, Underwood, Michael B., Fisher, Donald, McNeill, Lisa, Saffer, Demian, Ujiie, Kohtaro and Yamaguchi, Asuka eds. Geology and Tectonics of Subduction Zones: A Tribute to Gaku Kimura, Vol. 534. GSA Special Papers, Geological Society of America, (10.1130/2018.2534(12))

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Abstract

The subduction thrust interface represents a zone of concentrated deformation coupled to fluid generation, flow, and escape. Here, we review the internal structure of the megathrust as exposed in exhumed accretionary complexes, and we identify a deformation sequence that develops as material entering the trench is subducted through the seismogenic zone. Initial ductile flow in soft sediment generates dismembered, folded, and boudinaged bedding that is crosscut by later brittle discontinuities. Veins formed along early faults, and filling hydrofractures with the same extension directions as boudins in bedding, attest to fluid-assisted mass transfer during the shallow transition from ductile flow to brittle deformation. In higher-metamorphic-grade rocks, veins crosscut foliations defined by mineral assemblages stable at temperatures beyond those at the base of the seismogenic zone. The veins are, however, themselves ductilely deformed by diffusion and/or dislocation creep, and thus they record fracture and fluid flow at a deeper brittle-to-ductile transition.

Item Type: Book Section
Book Type: Edited Book
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Publisher: Geological Society of America
ISBN: 9780813725345
Date of First Compliant Deposit: 28 September 2018
Date of Acceptance: 25 September 2017
Last Modified: 19 Sep 2019 09:40
URI: http://orca-mwe.cf.ac.uk/id/eprint/115344

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