HR: 16:15h
AN: MR34A-02 [Abstracts]
TI: High-pressure creep of serpentine, interseismic deformation and initiation of subduction
AU: Reynard, B
EM: bruno.reynard@ens-lyon.fr
AF: Laboratoire des Sciences de la Terre, CNRS UMR 5570, Ecole normale superieure de
Lyon, Universite Claude Bernard Lyon 1, 46 allee d'Italie 69364, Lyon cedex 07, 69364, France
AU: * Hilairet, N
EM: nadege.hilairet@ens-lyon.fr
AF: Laboratoire des Sciences de la Terre, CNRS UMR 5570, Ecole normale superieure de
Lyon, Universite Claude Bernard Lyon 1, 46 allee d'Italie 69364, Lyon cedex 07, 69364, France
AU: Wang, Y
EM: wang@cars.uchicago.edu
AF: Center for Advanced Radiation Sources, The university of Chicago, 5640 S. Ellis Ave.,
Chicago, IL 60637, United States
AU: Daniel, I
EM: isabelle.daniel@univ-lyon1.fr
AF: Laboratoire des Sciences de la Terre, CNRS UMR 5570, Ecole normale superieure de
Lyon, Universite Claude Bernard Lyon 1, 2, rue Raphael Dubois, Villeurbanne, 69622, France
AU: Merkel, S
EM: sebastien.merkel@univ-lille1.fr
AF: Laboratoire de Structure et Proprietes de l'Etat Solide UMR CNRS 8008
Université des Sciences et Technologies de Lille, Batiment C6, Villeneuve d'Ascq, 59655,
France
AU: Petitgirard, S
EM: spetitgi@ens-lyon.fr
AF: Laboratoire des Sciences de la Terre, CNRS UMR 5570, Ecole normale superieure de
Lyon, Universite Claude Bernard Lyon 1, 46 allee d'Italie 69364, Lyon cedex 07, 69364, France
AU: Nishiyama, N
EM: nishiyama@mserv.sci.ehime-u.ac.jp
AF: Center for Advanced Radiation Sources, The university of Chicago, 5640 S. Ellis Ave.,
Chicago, IL 60637, United States
AB:
Serpentines, phyllosilicates resulting from mantle hydration, have a low viscosity compared with other mantle and
slab materials within subduction zones. They have a global geodynamic importance on the timescale of mantle
convection because a serpentinite layer may decouple the mantle wedge from the subducting slab, therefore
influencing plate tectonics regime on the Earth. The seismic implications are far reaching as serpentinite
rheology may govern stress build-up and downdip relaxation over the slab surface, which are critical parameters
for earthquake triggering and for the downdip extent of major ruptures.
However, limitation of apparatus has restricted previous high temperature deformation experiments on
serpentinites to pressures below 0.7 GPa, and the lack of data at relevant P-T impeded quantification of
serpentine rheology influence on subduction zones dynamics. We present in situ deformation experiments on the
high-pressure variety antigorite, at low strain rates and pressure-temperature (P-T) of 1 and 4 GPa and 200 to
500C, respectively, i.e. over most of the antigorite stability field, using the Deformation-DIA (D-DIA) apparatus
coupled with synchrotron X-ray at 13-BM-D at GSE-CARS (Advanced Photo Source). Strain rates and stresses
were obtained respectively from in-situ monitoring the sample length with X-ray radiographs, and azimuthal
dependence of d-spacings on diffraction patterns. The determined stress-strain curves were fitted to a power-law
equation including both temperature and pressure dependence.
Regardless of the temperature, serpentinized mantle at the slab surface has a low viscosity that allows localizing
the deformation and impeding stress build-up. The consequences of such a rheology for subduction zones
dynamics at short and long term include limitation of the downdip propagation of large earthquakes and viscous
relaxation as an origin of post-seismic deformations and slow earthquakes. The low viscosity of serpentinized
faults in the oceanic lithosphere makes them possible sites for subduction initiation.
DE: 3902 Creep and deformation
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
DE: 5120 Plasticity, diffusion, and creep
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting