Lattice preferred orientation of olivine aggregates deformed in simple shear
Lattice preferred orientation of olivine aggregates deformed in simple shear
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DOI：
10.1038/375774a0
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发表时间：
1995-06
期刊：
影响因子：
64.8
通讯作者：
Shuqing Zhang;S. Karato
中科院分区：
文献类型：
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作者：
Shuqing Zhang;S. Karato
地球上地幔的区域由于其组成矿物响应变形而采用的优选晶体取向（“晶格优选取向”）而显示出显著的地震各向异性1 -6。因此，地震各向异性提供了线索的流动和/或应力模式在上地幔，但使用晶格优选取向来推断这些属性从地震数据一直受到阻碍，缺乏相关的实验研究，在晶体取向的变化，简单的剪切变形。（简单剪切可能是上地幔变形的主要模式，而以前的大多数实验都集中在单轴压缩的影响上7 -9。）在这里，我们描述的橄榄石聚集体的简单剪切变形实验的结果，在高温和高压（~1,500 K和300 MPa）进行。对于大应变（高达150%），我们的实验再现了在高度变形的上地幔岩石中观察到的晶格择优取向，其中橄榄石[100]轴几乎平行于流动方向。但对于相对较小的应变，优选取向相对于流动方向旋转，这表明地震各向异性也应该对上地幔的剪切感敏感。
REGIONS of the Earth's upper mantle show significant seismic ani-sotropy due to the preferred crystallographic orientation ('lattice preferred orientation') adopted by its constituent minerals in response to deformation1–6. Seismic anisotropies thus provide clues to the flow and/or stress patterns in the upper mantle, but the use of lattice preferred orientation to infer such properties from seismic data has been hampered by the lack of experimental studies relating changes in crystallographic orientation to simple-shear deformation. (Simple shear is probably the dominant mode of deformation in the upper mantle, whereas most previous experiments have focused on the effects of uniaxial compression7–9.) Here we describe the results of simple-shear deformation experiments on olivine aggregates, conducted at high temperatures and pressures (~1,500 K and 300 MPa). For large strains (up to 150%), our experiments reproduce the lattice preferred orientation observed in highly deformed upper-mantle rocks, in which the olivine [100] axes lie nearly parallel to the flow direction. But for relatively small strains, the preferred orientation is rotated with respect to the flow direction, indicating that seismic anisotropy should also be sensitive to the sense of shear in the upper mantle.