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Science 22 June 2007:
Vol. 316. no. 5832, pp. 1729 - 1732
DOI: 10.1126/science.1140609
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Reports

Deformation of (Mg,Fe)SiO3 Post-Perovskite and D'' Anisotropy

Sébastien Merkel,1,2* Allen K. McNamara,3 Atsushi Kubo,4{dagger} Sergio Speziale,1{ddagger} Lowell Miyagi,1 Yue Meng,5 Thomas S. Duffy,4 Hans-Rudolf Wenk1

Polycrystalline (Mg0.9,Fe0.1)SiO3 post-perovskite was plastically deformed in the diamond anvil cell between 145 and 157 gigapascals. The lattice-preferred orientations obtained in the sample suggest that slip on planes near (100) and (110) dominate plastic deformation under these conditions. Assuming similar behavior at lower mantle conditions, we simulated plastic strains and the contribution of post-perovskite to anisotropy in the D'' region at the Earth core-mantle boundary using numerical convection and viscoplastic polycrystal plasticity models. We find a significant depth dependence of the anisotropy that only develops near and beyond the turning point of a downwelling slab. Our calculated anisotropies are strongly dependent on the choice of elastic moduli and remain hard to reconcile with seismic observations.

1 Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA.
2 Laboratoire de Structure et Propriétés de l'Etat Solide, UMR CNRS 8008, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq, France.
3 School of Earth and Space Exploration, Arizona State University, Box 871404, Tempe, AZ 85287–1404, USA.
4 Department of Geosciences, Princeton University, Princeton, NJ 08544, USA.
5 High-Pressure Collaborative Access Team, Carnegie Institution of Washington, Argonne, IL 60439, USA.

{dagger} Present address: Consortium for Advanced Radiation Sources, University of Chicago, Argonne, IL 60439, USA.

{ddagger} Present address: GeoForschungsZentrum Potsdam, Division 4.1, Telegrafenberg, 9-14482 Potsdam, Germany.

* To whom correspondence should be addressed. E-mail: sebastien.merkel{at}univ-lille1.fr

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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