Abstract
About 200 km above the core–mantle boundary, the D′′ seismic discontinuity marks the depth where magnesium silicate perovskite—the main mantle mineral—is transformed into its high-pressure phase of post-perovskite1,2. Observations of seismic anisotropy within the D′′ region are inferred to arise from textures within post-perovskite3,4,5 that are created by flow in the deep mantle. Specifically, mantle flow is thought to cause post-perovskite to deform, creating a lattice-preferred orientation within the post-perovskite6,7,8,9,10. However, it is difficult to explain all of the observed patterns of seismic anisotropy in the D′′ region from this deformation mechanism alone. Here we use a low-pressure fluoride analogue system11 to study the transformation from perovskite to post-perovskite in laboratory experiments. We find that post-perovskite can inherit texture from the perovskite phase. If a similar transformation mechanism operates in the Earth, post-perovskite will inherit textures from deformed perovskite and vice versa, as lower-mantle material passes into and out of the D′′ region. We find that this textural inheritance, combined with lattice-preferred orientation in post-perovskite, can explain the observed patterns of anisotropy in the lowermost mantle.
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Acknowledgements
This work was supported by a Natural Environment Research Council grant to D.P.D. (ref J009520) and a European Research Council starting grant to F.N. (ref 307312). A.W. was supported by ERC grant 240473.
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High-pressure experiments D.P.D. and C.L.; XRD experiments F.N., M.A., N.C. and D.P.D.; TEM experiments N.M.; crystallographic interpretation I.G.W. and D.P.D.; seismic anisotropy simulations A.M.W.
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Dobson, D., Miyajima, N., Nestola, F. et al. Strong inheritance of texture between perovskite and post-perovskite in the D′′ layer. Nature Geosci 6, 575–578 (2013). https://doi.org/10.1038/ngeo1844
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DOI: https://doi.org/10.1038/ngeo1844
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