Lattice-Preferred Orientation of Lower Mantle Materials and Seismic Anisotropy in the D″ Layer

Daisuke Yamazaki, Shun Ichiro Karato

    Research output: Chapter in Book/Report/Conference proceedingChapter

    7 Citations (Scopus)

    Abstract

    Results of experimental studies and theoretical calculations on deformation of " layer minerals are reviewed. We conclude that only the results from the experiments under high temperature and modest stress conditions are potentially applicable to the deformation fabrics in the " layer. For perovskite and post-perovskite, such experimental data are available only for analog materials. By combining those results with elastic properties, we investigate the nature of seismic anisotropy corresponding to a given deformation geometry. Both azimuthal and polarization anisotropies are expected for all minerals. For horizontal flow, perovskite will produce VSV>VSH anisotropy whereas (Mg,Fe)O shows VSH>VSV anisotropy. VSH/VSV anisotropy caused by post-perovskite depends on the elastic anisotropy and the dominant glide plane, both of which are not well constrained. If we choose (010) as a glide plane, weak VSH>VSV or VSV>VSH anisotropy will develop for shear deformation of post-perovskite depending on the elastic constants. For this glide plane, the magnitude of the anisotropy of (Mg,Fe)O is much larger than that for post-perovskite. For a vertical cylindrical flow expected for upwelling mantle plumes, VSV>VSH anisotropy is expected for both (Mg,Fe)O and post-perovskite but not for perovskite. We conclude that (Mg,Fe)O plays a more important role than post-perovskite for the interpretation of seismic anisotropy in both circum Pacific and the central Pacific " layer. In the circum Pacific regions, the seismic anisotropy can be attributed to the deformation-induced lattice-preferred orientation of (Mg,Fe)O and post-perovskite, whereas some additional contribution from aligned melt pocket might be important in the central Pacific.

    Original languageEnglish
    Title of host publicationPost-Perovskite
    Subtitle of host publicationThe Last Mantle Phase Transition
    Publisherwiley
    Pages69-78
    Number of pages10
    ISBN (Electronic)9781118666401
    ISBN (Print)9780875904399
    DOIs
    Publication statusPublished - Mar 19 2013

    ASJC Scopus subject areas

    • Physics and Astronomy(all)

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