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Title
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Stress-induced amorphization triggers deformation in the lithospheric mantle
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Author
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Abstract
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| The mechanical properties of olivine-rich rocks are key to determining the mechanical coupling between Earth's lithosphere and asthenosphere. In crystalline materials, the motion of crystal defects is fundamental to plastic flow(1-4.) However, because the main constituent of olivine-rich rocks does not have enough slip systems, additional deformation mechanisms are needed to satisfy strain conditions. Experimental studies have suggested a non-Newtonian, grain-size-sensitive mechanism in olivine involving grain-boundary sliding(5,6). However, very few microstructural investigations have been conducted on grain-boundary sliding, and there is no consensus on whether a single or multiple physical mechanisms are at play. Most importantly, there are no theoretical frameworks for incorporating the mechanics of grain boundaries in polycrystalline plasticity models. Here we identify a mechanism for deformation at grain boundaries in olivine-rich rocks. We show that, in forsterite, amorphization takes place at grain boundaries under stress and that the onset of ductility of olivine-rich rocks is due to the activation of grain-boundary mobility in these amorphous layers. This mechanism could trigger plastic processes in the deep Earth, where high-stress conditions are encountered (for example, at the brittle-plastic transition). Our proposed mechanism is especially relevant at the lithosphere-asthenosphere boundary, where olivine reaches the glass transition temperature, triggering a decrease in its viscosity and thus promoting grain-boundary sliding. |
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Language
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English
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Source (journal)
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Nature. - London, 1869, currens
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Related dataset(s)
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Publication
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London
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MacMillan
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2021
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ISSN
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0028-0836
[print]
1476-4687
[online]
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DOI
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10.1038/S41586-021-03238-3
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Volume/pages
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591
:7848
(2021)
, p. 82-86
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ISI
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000626921700014
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Pubmed ID
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33658696
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Full text (Publisher's DOI)
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Full text (open access)
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Full text (publisher's version - intranet only)
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