Letter | Published:

Modelling the rheology of MgO under Earth’s mantle pressure, temperature and strain rates

Nature volume 481, pages 177180 (12 January 2012) | Download Citation

Abstract

Plate tectonics, which shapes the surface of Earth, is the result of solid-state convection in Earth’s mantle over billions of years. Simply driven by buoyancy forces, mantle convection is complicated by the nature of the convecting materials, which are not fluids but polycrystalline rocks. Crystalline materials can flow as the result of the motion of defects—point defects, dislocations, grain boundaries and so on. Reproducing in the laboratory the extreme deformation conditions of the mantle is extremely challenging. In particular, experimental strain rates are at least six orders of magnitude larger than in nature1. Here we show that the rheology of MgO at the pressure, temperature and strain rates of the mantle is accessible by multiscale numerical modelling starting from first principles and with no adjustable parameters. Our results demonstrate that extremely low strain rates counteract the influence of pressure. In the mantle, MgO deforms in the athermal regime and this leads to a very weak phase. It is only in the lowermost lower mantle that the pressure effect could dominate and that, under the influence of lattice friction, a viscosity of the order of 1021–1022 pascal seconds can be defined for MgO.

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Acknowledgements

This work was supported by ANR (Diup project).

Author information

Affiliations

  1. Université Lille 1, Unité Matériaux et Transformations, UMR CNRS 8207, F-59650 Villeneuve d’Ascq, France

    • Patrick Cordier
    • , Jonathan Amodeo
    •  & Philippe Carrez

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Contributions

P.C. conceived the project. P.C. and Ph.C. designed the work. J.A. and Ph.C. performed numerical simulations. All authors discussed and interpreted the results. P.C. wrote the paper with feedback and contributions from all co-authors.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Patrick Cordier or Philippe Carrez.

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    Supplementary Information

    The file contains Supplementary Text and Data, Supplementary Tables 1-4, Supplementary Figures 1-6 with legends and additional references.

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DOI

https://doi.org/10.1038/nature10687

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