Cordier, Patrick and Gouriet, Karine and Weidner, Timmo and Van Orman, James and Castelnau, Olivier and Jackson, Jennifer M. and Carrez, Philippe (2023) Periclase deforms more slowly than bridgmanite under mantle conditions. Nature, 613 (7943). pp. 303-307. ISSN 0028-0836. doi:10.1038/s41586-022-05410-9. https://resolver.caltech.edu/CaltechAUTHORS:20230224-720983000.1
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Abstract
Transport of heat from the interior of the Earth drives convection in the mantle, which involves the deformation of solid rocks over billions of years. The lower mantle of the Earth is mostly composed of iron-bearing bridgmanite MgSiO₃ and approximately 25% volume periclase MgO (also with some iron). It is commonly accepted that ferropericlase is weaker than bridgmanite. Considerable progress has been made in recent years to study assemblages representative of the lower mantle under the relevant pressure and temperature conditions. However, the natural strain rates are 8 to 10 orders of magnitude lower than in the laboratory, and are still inaccessible to us. Once the deformation mechanisms of rocks and their constituent minerals have been identified, it is possible to overcome this limitation thanks to multiscale numerical modelling, and to determine rheological properties for inaccessible strain rates. In this work we use 2.5-dimensional dislocation dynamics to model the low-stress creep of MgO periclase at lower mantle pressures and temperatures. We show that periclase deforms very slowly under these conditions, in particular, much more slowly than bridgmanite deforming by pure climb creep. This is due to slow diffusion of oxygen in periclase under pressure. In the assemblage, this secondary phase hardly participates in the deformation, so that the rheology of the lower mantle is very well described by that of bridgmanite. Our results show that drastic changes in deformation mechanisms can occur as a function of the strain rate.
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Additional Information: | We acknowledge funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 787198—TimeMan and from the National Science Foundation’s (NSF) Collaborative Study of Earth’s Deep Interior under EAR-1161046 and EAR-2009935. We are thankful to the CIDER programme set at the Kavli Institute for Theoretical Physics, University of California, Santa Barbara (NSF EAR−1135452, funded under the FESD Program). Contributions. The study was designed by P. Cordier, K.G. and T.W. performed the dislocation dynamics calculations. O.C. performed the micromechanical (self-consistent) calculations. P. Cordier, K.G., T.W., J.V.O., O.C., J.M.J. and P. Carrez discussed and analysed the data. P. Cordier wrote the paper with contributions from all authors. Data availability. The data of this manuscript are available at https://doi.org/10.5281/zenodo.5970733. Source data are provided with this paper. Code availability. The source code of the 2.5D DD is available at https://doi.org/10.5281/zenodo.6306546. The authors declare no competing interests. | ||||||||||||||||||
Group: | Division of Geological and Planetary Sciences | ||||||||||||||||||
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Issue or Number: | 7943 | ||||||||||||||||||
DOI: | 10.1038/s41586-022-05410-9 | ||||||||||||||||||
Record Number: | CaltechAUTHORS:20230224-720983000.1 | ||||||||||||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20230224-720983000.1 | ||||||||||||||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||||||||||||||
ID Code: | 119501 | ||||||||||||||||||
Collection: | CaltechAUTHORS | ||||||||||||||||||
Deposited By: | George Porter | ||||||||||||||||||
Deposited On: | 25 Feb 2023 18:44 | ||||||||||||||||||
Last Modified: | 25 Feb 2023 18:44 |
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