Development of anisotropic contiguity in deforming partially molten aggregates: 2. Implications for the lithosphere‐asthenosphere boundary
Development of anisotropic contiguity in deforming partially molten aggregates: 2. Implications for the lithosphere‐asthenosphere boundary
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部分熔融聚集体变形中各向异性邻接的发展：2. 对岩石圈-软流圈边界的影响
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发表时间：
2015
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通讯作者：
T. Drombosky
中科院分区：
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作者：
S. Hier‐Majumder;T. Drombosky
本文计算了纯剪切变形和简单剪切变形中熔体再分布引起的地震各向异性。变形强烈修改最初占据三个晶粒交界处的熔体的几何形状。晶间接触的最初各向同性的部分区域，邻接，由于变形而变得各向异性。因此，在平行于最大压应力轴的平面上评估的邻接分量减小。在两种变形模式下，邻接张量的迹线几乎保持不变。在配套文章[标记为DHM]中，我们概述了数值方法，并从我们的数值变形实验中给出了合成显微照片。在纯剪切变形中，主接触方向保持静止，而它们在简单剪切期间旋转。的邻接张量的主成分之间的比率从1在未变形的聚集体减少到0.1后，在纯剪切缩短45%，并在简单剪切应变为0.75后，为0.3。在纯剪切和简单剪切实验中，剪切波速度的各向异性随应变以强非线性方式增加。在纯剪切变形中，稳态微结构在垂直和平行于熔体膜平面振动的剪切波之间产生近3%的各向异性。
In this article, we calculate the seismic anisotropy resulting from melt redistribution during pure and simple shear deformation. Deformation strongly modifies the geometry of melts initially occupying three grain junctions. The initially isotropic fractional area of intergranular contact, contiguity, becomes anisotropic due to deformation. Consequently, the component of contiguity evaluated on the plane parallel to axis of maximum compressive stress decreases. During both modes of deformation, the trace of the contiguity tensor remains nearly unchanged. In the companion article [labeled DHM], we outline the numerical methods and present the synthetic micrographs from our numerical deformation experiments. In pure shear deformation, the principal contiguity directions remain stationary while they rotate during simple shear. The ratio between the principal components of the contiguity tensor decrease from 1 in an undeformed aggregate to 0.1 after 45% shortening in pure shear and to 0.3 after a shear strain of 0.75 in simple shear. In both pure and simple shear experiments, anisotropy in the shear wave velocity increases with the strain in a strongly nonlinear fashion. In pure shear deformation, the steady state microstructure produces nearly 3% anisotropy between shear waves vibrating perpendicular and parallel to the planes of melt films.