HR: 0800h
AN: DI51A-0284    [Abstracts]
TI: Serpentine Rheology and Dehydration at High-Pressure, Implications for Intermediate-depth Seismicity
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, Lyon cedex 07, 69364, France
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, 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@ens-lyon.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
AB: Serpentinites have a lower viscosity than other mantle and slab materials within subduction zones. Serpentine dehydration is believed to play a major role in intermediate-depth seismicity, and several mechanisms have been proposed such as dehydration embrittlement and shear heating. However, quantifying the influence of serpentine rheology and its dehydration on strain rates and stress distribution within subduction zones has remained beyond reach, because of the lack of experimental data on deformation of the high-pressure variety antigorite, at relevant P and T conditions. Antigorite deformation experiments were carried out both within its stability field and during dehydration, over a pressure temperature (P-T) range of 1 - 4 GPa and 200-600 /deg C, at strain rates between ~10-4 and 10-6 s-1, in a D-DIA apparatus 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 within antigorite stability field were fitted to a power-law equation including both temperature and pressure dependence. At the lowest strain rate investigated and nominal T within the antigorite stability field, localization occurred accompanied by local dehydration and a moderate increase in strain rate. Whatever the reaction and the sign of the volume change, dehydration induced an increase in strain rate. The present results show that antigorite rheology is likely to govern stress building-up and relaxation at the slab surface during interseismic time. We will discuss the implications of the results from the dehydration experiments for the role of serpentinites in intermediate-depth seismicity within subduction zones.
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
DE: 5120 Plasticity, diffusion, and creep
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8166 Stresses: deep-seated
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting