Mantle dynamics inferred from the crystallographic preferred orientation of bridgmanite
Mantle dynamics inferred from the crystallographic preferred orientation of bridgmanite
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DOI：
10.1038/nature19777
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发表时间：
2016-10
期刊：
影响因子：
64.8
通讯作者：
N. Tsujino;Yu Nishihara;D. Yamazaki;Y. Seto;Y. Higo;E. Takahashi
中科院分区：
文献类型：
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作者：
N. Tsujino;Yu Nishihara;D. Yamazaki;Y. Seto;Y. Higo;E. Takahashi
在几个俯冲板块周围的地球最上部下地幔中观测到地震横波各向异性。变形诱导晶体择优取向（CPO）的Bridgmanite（钙钛矿结构的（Mg，Fe）SiO 3）所造成的各向异性是这些地震观测的最合理的解释。然而，硼镁石的流变特性在很大程度上是未知的。单轴变形实验已被用来确定桥镁石的变形结构，但主导滑移系（滑移方向和滑移面）尚未确定。在这里，我们报告的CPO模式和优势的Bridgmanite滑移系统的条件下，对应于最上层的下地幔（25吉帕斯卡和1,873开尔文），通过简单的剪切变形实验，使用河井型变形DIA设备。所得到的组构在垂直于剪切面方向上以[100]为特征，在平行于剪切方向上以[001]为特征，表明桥镁石的主要滑移系为[001]（100）。在几个俯冲板块（汤加-克马德克、千岛、秘鲁和爪哇）附近观测到的地震横波各向异性可以用平行于俯冲方向的地幔流引起的桥镁石的CPO来解释。
Seismic shear wave anisotropy,,,,,is observed in Earth’s uppermost lower mantle around several subducted slabs. The anisotropy caused by the deformation-induced crystallographic preferred orientation (CPO) of bridgmanite (perovskite-structured (Mg,Fe)SiO3) is the most plausible explanation for these seismic observations. However, the rheological properties of bridgmanite are largely unknown. Uniaxial deformation experiments,,have been carried out to determine the deformation texture of bridgmanite, but the dominant slip system (the slip direction and plane) has not been determined. Here we report the CPO pattern and dominant slip system of bridgmanite under conditions that correspond to the uppermost lower mantle (25 gigapascals and 1,873 kelvin) obtained through simple shear deformation experiments using the Kawai-type deformation-DIA apparatus. The fabrics obtained are characterized by [100] perpendicular to the shear plane and [001] parallel to the shear direction, implying that the dominant slip system of bridgmanite is [001](100). The observed seismic shear- wave anisotropies near several subducted slabs,,,(Tonga–Kermadec, Kurile, Peru and Java) can be explained in terms of the CPO of bridgmanite as induced by mantle flow parallel to the direction of subduction.