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Open AccessArticle

Competing Deformation Mechanisms in Periclase: Implications for Lower Mantle Anisotropy

Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, USA
Kansas Water Resource Center, United States Geological Survey, 1204 Canterbury Dr, Hays, KS 67601, USA
Author to whom correspondence should be addressed.
Minerals 2019, 9(11), 650;
Received: 1 September 2019 / Revised: 21 October 2019 / Accepted: 22 October 2019 / Published: 23 October 2019
(This article belongs to the Special Issue Texture and Microstructural Analysis of Crystalline Solids)
Seismic anisotropy is observed above the core-mantle boundary in regions of slab subduction and near the margins of Large Low Shear Velocity Provinces (LLSVPs). Ferropericlase is believed to be the second most abundant phase in the lower mantle. As it is rheologically weak, it may be a dominant source for anisotropy in the lowermost mantle. Understanding deformation mechanisms in ferropericlase over a range of pressure and temperature conditions is crucial to interpret seismic anisotropy. The effect of temperature on deformation mechanisms of ferropericlase has been established, but the effects of pressure are still controversial. With the aim to clarify and quantify the effect of pressure on deformation mechanisms, we perform room temperature compression experiments on polycrystalline periclase to 50 GPa. Lattice strains and texture development are modeled using the Elasto-ViscoPlastic Self Consistent method (EVPSC). Based on modeling results, we find that { 110 } 1 1 ¯ 0 slip is increasingly activated with higher pressure and is fully activated at ~50 GPa. Pressure and temperature have a competing effect on activities of dominant slip systems. An increasing { 100 } 011 : { 110 } 1 1 ¯ 0 ratio of slip activity is expected as material moves from cold subduction regions towards hot upwelling region adjacent to LLSVPs. This could explain observed seismic anisotropy in the circum-Pacific region that appears to weaken near margins of LLVSPs. View Full-Text
Keywords: periclase; deformation; high pressure; texture; plasticity modeling; anisotropy; D″ periclase; deformation; high pressure; texture; plasticity modeling; anisotropy; D″
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Lin, F.; Couper, S.; Jugle, M.; Miyagi, L. Competing Deformation Mechanisms in Periclase: Implications for Lower Mantle Anisotropy. Minerals 2019, 9, 650.

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