| DOI: | 10.1016/j.epsl.2018.03.032
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| Scopus记录号: | 2-s2.0-85045051519
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| 论文题名: | Deformation, crystal preferred orientations, and seismic anisotropy in the Earth's D″ layer |
| 作者: | Tommasi A.; Goryaeva A.; Carrez P.; Cordier P.; Mainprice D.
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| 刊名: | Earth and Planetary Science Letters
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| ISSN: | 0012821X
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| 出版年: | 2018
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| 卷: | 492 | | 起始页码: | 35
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| 结束页码: | 46
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| 语种: | 英语
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| 英文关键词: | deformation modeling
; D″ layer
; ferropericlase
; mantle convection
; post-perovskite
; seismic anisotropy
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| Scopus关键词: | Anisotropy
; Birefringence
; Crystal orientation
; Deformation
; Dislocations (crystals)
; Iridium compounds
; Magnesia
; Nitrogen compounds
; Parallel flow
; Perovskite
; Polarization
; Seismology
; Shear flow
; Shear waves
; Silicon compounds
; Wave propagation
; Deformation modeling
; Ferropericlase
; Mantle convection
; Post perovskite
; Seismic anisotropy
; Uranium compounds
; core-mantle boundary
; deformation
; mantle convection
; modeling
; perovskite
; preferred orientation
; S-wave
; seismic anisotropy
; seismic velocity
; wave splitting
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| 英文摘要: | We use a forward multiscale model that couples atomistic modeling of intracrystalline plasticity mechanisms (dislocation glide ± twinning) in MgSiO3 post-perovskite (PPv) and periclase (MgO) at lower mantle pressures and temperatures to polycrystal plasticity simulations to predict crystal preferred orientations (CPO) development and seismic anisotropy in D″. We model the CPO evolution in aggregates of 70% PPv and 30% MgO submitted to simple shear, axial shortening, and along corner-flow streamlines, which simulate changes in flow orientation similar to those expected at the transition between a downwelling and flow parallel to the core–mantle boundary (CMB) within D″ or between CMB-parallel flow and upwelling at the borders of the large low shear wave velocity provinces (LLSVP) in the lowermost mantle. Axial shortening results in alignment of PPv [010] axes with the shortening direction. Simple shear produces PPv CPO with a monoclinic symmetry that rapidly rotates towards parallelism between the dominant [100](010) slip system and the macroscopic shear. These predictions differ from MgSiO3 post-perovskite textures formed in diamond-anvil cell experiments, but agree with those obtained in simple shear and compression experiments using CaIrO3 post-perovskite. Development of CPO in PPv and MgO results in seismic anisotropy in D″. For shear parallel to the CMB, at low strain, the inclination of ScS, Sdiff, and SKKS fast polarizations and delay times vary depending on the propagation direction. At moderate and high shear strains, all S-waves are polarized nearly horizontally. Downwelling flow produces Sdiff, ScS, and SKKS fast polarization directions and birefringence that vary gradually as a function of the back-azimuth from nearly parallel to inclined by up to 70° to CMB and from null to ∼5%. Change in the flow to shear parallel to the CMB results in dispersion of the CPO, weakening of the anisotropy, and strong azimuthal variation of the S-wave splitting up to 250 km from the corner. Transition from horizontal shear to upwelling also produces weakening of the CPO and complex seismic anisotropy patterns, with dominantly inclined fast ScS and SKKS polarizations, over most of the upwelling path. Models that take into account twinning in PPv explain most observations of seismic anisotropy in D″, but heterogeneity of the flow at scales <1000 km is needed to comply with the seismological evidence for low apparent birefringence in D″. © 2018 The Author(s) |
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| 资源类型: | 期刊论文
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/109899
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| Appears in Collections: | 影响、适应和脆弱性
气候变化事实与影响
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作者单位: | Geosciences Montpellier, CNRS, Université de Montpellier, Montpellier cedex 5, F-34095, France; Univ. Lille, CNRS, INRA, ENSCL, UMR 8207, UMET – Unité Matériaux et Transformations, Lille, F-59000, France
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| Recommended Citation: | |
Tommasi A.,Goryaeva A.,Carrez P.,et al. Deformation, crystal preferred orientations, and seismic anisotropy in the Earth's D″ layer[J]. Earth and Planetary Science Letters,2018-01-01,492
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