Stress‐induced anisotropy of partially molten rock analogue deformed under quasi‐static loading test
Stress‐induced anisotropy of partially molten rock analogue deformed under quasi‐static loading test
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DOI：
10.1029/2009jb006568
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发表时间：
2010-03
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通讯作者：
Y. Takei
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文献类型：
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作者：
Y. Takei
[1]在部分熔融岩石模拟物上进行了两次准静态加载试验，一次在主应力方向上重复变化，另一次在主应力方向上不重复变化。在这两个运行中，通过使用超声剪切波的样品微观结构的连续的，非破坏性的监测观察到应力诱导的各向异性的发展。剪切波各向异性的方向表明，法线几乎平行于σ3方向的颗粒间接触面面积减小，而其他接触面面积几乎保持不变。这种微结构各向异性引起的大的粘性各向异性可以通过剪切和各向同性应力分量之间的强耦合来检测。相对于剪切波（弹性）各向异性的小振幅，粘性各向异性的大振幅与理论模型的预测一致。这种各向异性的幅度和方向几乎与剪切应力的幅度和方向同步，表明在给定的剪切应力下存在稳态微结构。一个小的滞后，但是，也观察到，这导致了显着的晶界润湿，由于在剪切方向上的反复变化。结果表明，弹性和粘性理论模型的有效性。由粘性各向异性产生的剪切分量和各向同性分量之间的耦合显著地影响部分熔融地幔的动力学，因为它增强了剪切诱导的熔体偏析。
[1] Two quasi-static loading tests one with and one without repeated changes in the principal stress directions were performed on a partially molten rock analogue. In both runs, development of stress-induced anisotropy was observed through a continuous, nondestructive monitoring of the sample microstructure using ultrasonic shear waves. The direction of the shear wave anisotropy showed that the area of the grain-to-grain contact faces whose normals are nearly parallel to the σ3 direction decreased, while the area of the other contact faces remained almost unchanged. Large viscous anisotropy caused by this microstructural anisotropy could be detected through the strong coupling between shear and isotropic stress components. The large amplitude of viscous anisotropy relative to the small amplitude of shear wave (elastic) anisotropy is consistent with the prediction from theoretical models. Amplitude and direction of this anisotropy almost synchronized with those of shear stress, indicating the existence of steady state microstructure under a given shear stress. A small hysteresis, however, was also observed, which led to a significant grain boundary wetting due to the repeated changes in the shear direction. The present results show the validity of the theoretical models for elasticity and viscosity. The coupling between shear and isotropic components produced by viscous anisotropy significantly affects the dynamics of partially molten mantle, because it enhances shear-induced melt segregation.