Velocity and density characteristics of subducted oceanic crust and the origin of lower-mantle heterogeneities

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作者：
Wenzhong Wang
Yinhan Xu
Daoyuan Sun
Sidao Ni
Renata Wentzcovitch
Zhongqing Wu
机构：
[1] University of Science and Technology of China,Laboratory of Seismology and Physics of Earth’s Interior, School of Earth and Space Sciences
[2] CAS Center for Excellence in Comparative Planetology,State Key Laboratory of Geodesy and Earth’s Dynamics, Institute of Geodesy and Geophysics
[3] Chinese Academy of Sciences,Department of Applied Physics and Applied Mathematics
[4] Columbia University,Department of Earth and Environmental Sciences
[5] Columbia University,Lamont–Doherty Earth Observatory
[6] Columbia University,undefined
来源：
Nature Communications | / 11卷
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摘要：
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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