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Dislocation creep in MgSiO3 perovskite at conditions of the Earth's uppermost lower mantle

Nature volume 428, pages 837840 (22 April 2004) | Download Citation

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Abstract

Seismic anisotropy provides an important observational constraint on flow in the Earth's deep interior. The quantitative interpretation of anisotropy, however, requires knowledge of the slip geometry of the constitutive minerals that are responsible for producing rock fabrics. The Earth's lower mantle is mostly composed of (Mg, Fe)SiO3 perovskite1, but as MgSiO3 perovskite is not stable at high temperature under ambient pressure, it has not been possible to investigate its mechanical behaviour with conventional laboratory deformation experiments. To overcome this limitation, several attempts were made to infer the mechanical properties of MgSiO3 perovskite on the basis of analogue materials2,3,4,5,6,7. But perovskites do not constitute an analogue series for plastic deformation, and therefore the direct investigation of MgSiO3 perovskite is necessary. Here we have taken advantage of recent advances in experimental high-pressure rheology8 to perform deformation experiments on coarse-grained MgSiO3 polycrystals under pressure and temperature conditions of the uppermost lower mantle. We show that X-ray peak broadening measurements developed in metallurgy can be adapted to low-symmetry minerals to identify the elementary deformation mechanisms activated under these conditions. We conclude that, under uppermost lower-mantle conditions, MgSiO3 perovskite deforms by dislocation creep and may therefore contribute to producing seismic anisotropy in rocks at such depths.

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Acknowledgements

High-pressure experiments were performed at the Bayerisches Geoinstitut under the EU ‘IHP–Access to Research Infrastructures’ programme. P.C. benefited from a ‘Congé thématique pour recherche’ from the University of Lille and from continuous support from INSU (‘Intérieur de la Terre’ programme). T.U. and G.T. thank the Hungarian Science Foundation for supporting this work

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Affiliations

  1. Laboratoire de Structure et Propriétés de l'Etat Solide, UMR CNRS 8008, Université des Sciences et Technologies de Lille, F-59655 Villeneuve d'Ascq Cedex, France

    • Patrick Cordier
  2. Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany

    • Patrick Cordier
  3. Department of General Physics, Eötvös University Budapest, H-1518 POB 32, Budapest, Hungary

    • Tamás Ungár
    •  & Lehel Zsoldos
  4. Department of Solid State Physics, Eötvös University Budapest, H-1518 POB 32, Budapest, Hungary

    • Géza Tichy

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The authors declare that they have no competing financial interests.

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Correspondence to Patrick Cordier.

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https://doi.org/10.1038/nature02472

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