Periclase deforms more slowly than bridgmanite under mantle conditions
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.
Additional Information
This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. 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.Attached Files
Published - s41586-022-05410-9.pdf
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Additional details
- PMCID
- PMC9834053
- Eprint ID
- 119501
- Resolver ID
- CaltechAUTHORS:20230224-720983000.1
- 787198
- European Research Council (ERC)
- EAR-1161046
- NSF
- EAR-2009935
- NSF
- EAR-1135452
- NSF
- Created
-
2023-02-25Created from EPrint's datestamp field
- Updated
-
2023-07-10Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences