HR: 14:10h
AN: T13D-03 INVITED [Abstracts]
TI: Pressure Sensitivity of Olivine Slip Systems: Evidence From High-Pressure Deformation
Experiments
AU: * Cordier, P
EM: Patrick.Cordier@univ-lille1.fr
AF: Laboratoire de Structure et proprietes de l'Etat Solide, UMR CNRS 8008, Universit‚ de Lille 1,
Villeneuve d'Ascq, F-59655
France
AU: Couvy, H
EM: Helene.Couvy@uni-bayreuth.de
AF: Laboratoire de Structure et proprietes de l'Etat Solide, UMR CNRS 8008, Universit‚ de Lille 1,
Villeneuve d'Ascq, F-59655
France
AU: Couvy, H
EM: Helene.Couvy@uni-bayreuth.de
AF: Bayerisches Geoinstitut, Universitaet Bayreuth, Bayreuth, D-95440
Germany
AU: Raterron, P
EM: Paul.Raterron@univ-lille1.fr
AF: Laboratoire de Structure et proprietes de l'Etat Solide, UMR CNRS 8008, Universit‚ de Lille 1,
Villeneuve d'Ascq, F-59655
France
AU: Durinck, J
EM: Julien.Durinck@univ-lille1.fr
AF: Laboratoire de Structure et proprietes de l'Etat Solide, UMR CNRS 8008, Universit‚ de Lille 1,
Villeneuve d'Ascq, F-59655
France
AU: Mainprice, D
EM: David.Mainprice@dstu.univ-montp2.fr
AF: Laboratoire de Tectonophysique, UMR CNRS 5568, Universit‚ de Montpellier II, Montpellier, F-34095
France
AU: Tommasi, A
EM: Andrea.Tommasi@dstu.univ-montp2.fr
AF: Laboratoire de Tectonophysique, UMR CNRS 5568, Universit‚ de Montpellier II, Montpellier, F-34095
France
AB:
The mineral olivine dominates the composition of the Earth's upper mantle and hence controls its mechanical behavior and
physical properties such as viscosity and seismic anisotropy. Until recently our understanding of olivine rheology relied on
experimental work carried out at high temperature and moderate pressure and on extensive data on naturally deformed mantle
rocks outcropping at the Earth's surface. Pressure extrapolation was thus necessary to infer mantle rheology. We have carried
out a series of high-pressure deformation experiments on olivine polycrystals at 1300-1400øC and mantle pressures - ranging
from 2 to 11 GPa - using the multianvil apparatus and the deformation-DIA (D-DIA). Microstructural investigations by
transmission electron microscopy and crystal preferred orientations determined by electron back-scattered diffraction show
that [001] slip becomes predominant at high pressure. Further experiments were carried out on single crystals in a D-DIA
coupled with x-ray synchrotron radiation to determine in situ the rheological laws corresponding to the activation of
[100](010) and [001](010) slips. It is shown that the inversion that is stress sensitive takes place between 3 and 7 GPa in
the experiments. Ab-initio calculations of generalized stacking faults in olivine shows that [100] glide induces more
dilation than [001] glide, providing a first tentative explanation for this differential pressure sensitivity. [001] slip
produces crystal preferred orientations with an extremely low seismic anisotropy. Transition from [100] to [001] slip in
olivine may therefore explain the fast decrease in P and S waves anisotropy in the upper-mantle below 250 km .
DE: 5120 Plasticity, diffusion, and creep
DE: 3902 Creep and deformation
DE: 3924 High-pressure behavior
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting