Oriented grain growth and modification of ‘frozen anisotropy’ in the lithospheric mantle
Oriented grain growth and modification of ‘frozen anisotropy’ in the lithospheric mantle
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DOI：
10.1016/j.epsl.2017.06.050
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发表时间：
2017-09
影响因子：
5.3
通讯作者：
Y. Boneh;D. Wallis;L. Hansen;M. Krawczynski;P. Skemer
中科院分区：
文献类型：
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作者：
Y. Boneh;D. Wallis;L. Hansen;M. Krawczynski;P. Skemer
整个海洋岩石圈的地震各向异性通常被认为是由靠近洋脊的软流圈温度变形过程中形成的化石纹理产生的。在这里，我们研究高温高压静态退火对先前变形橄榄石聚集体的织构的影响，以模拟变形橄榄岩在岩石圈中的居住情况。我们的实验表明，由于低位错密度的晶粒优先生长，晶体择优取向（CPO）的取向和大小将发生变化。这些观察结果表明，纹理和存储的弹性应变能促进了一种晶粒生长方式，从而改变了变形骨料的 CPO。我们证明这些微观结构的变化改变了地震波速度和各向异性的方向分布和幅度。因此，静态退火可能会使根据岩石圈地震各向异性推断过去变形运动学变得复杂。
Seismic anisotropy throughout the oceanic lithosphere is often assumed to be generated by fossilized texture formed during deformation at asthenospheric temperatures close to the ridge. Here we investigate the effect of high-temperature and high-pressure static annealing on the texture of previously deformed olivine aggregates to simulate residence of deformed peridotite in the lithosphere. Our experiments indicate that the orientation and magnitude of crystallographic preferred orientation (CPO) will evolve due to the preferential growth of grains with low dislocation densities. These observations suggest that texture and stored elastic strain energy promote a style of grain growth that modifies the CPO of a deformed aggregate. We demonstrate that these microstructural changes alter the orientation distributions and magnitudes of seismic wave velocities and anisotropy. Therefore, static annealing may complicate the inference of past deformation kinematics from seismic anisotropy in the lithosphere.