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  • Title: Velocity and density characteristics of subducted oceanic crust and the origin of lower-mantle heterogeneities.
    Author: Wang W, Xu Y, Sun D, Ni S, Wentzcovitch R, Wu Z.
    Journal: Nat Commun; 2020 Jan 07; 11(1):64. PubMed ID: 31911578.
    Abstract:
    Seismic heterogeneities detected in the lower mantle were proposed to be related to subducted oceanic crust. However, the velocity and density of subducted oceanic crust at lower-mantle conditions remain unknown. Here, we report ab initio results for the elastic properties of calcium ferrite-type phases and determine the velocities and density of oceanic crust along different mantle geotherms. We find that the subducted oceanic crust shows a large negative shear velocity anomaly at the phase boundary between stishovite and CaCl2-type silica, which is highly consistent with the feature of mid-mantle scatterers. After this phase transition in silica, subducted oceanic crust will be visible as high-velocity heterogeneities as imaged by seismic tomography. This study suggests that the presence of subducted oceanic crust could provide good explanations for some lower-mantle seismic heterogeneities with different length scales except large low shear velocity provinces (LLSVPs).
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