The structure and composition of olivine grain boundaries: 40 years of studies, status and current developments
The structure and composition of olivine grain boundaries: 40 years of studies, status and current developments
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DOI：
10.1007/s00269-017-0935-9
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发表时间：
2018-01
影响因子：
1.4
通讯作者：
K. Marquardt;U. Faul;U. Faul
中科院分区：
文献类型：
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作者：
K. Marquardt;U. Faul;U. Faul
岩石中的界面，特别是橄榄石为主的岩石中的晶界，已经进行了大约40年的研究。晶界结构与性质的关系是理解多晶样品与单晶样品的发散特性的基础。直接结构观察的数量很少，即在100微米的范围内，直接与结构观察有关的属性的测量数量甚至更少。大块骨料的地震衰减、流变性和电导率等特性对颗粒大小很敏感，而且似乎受到晶界特征分布的影响。在此背景下，我们回顾了以前关于晶界结构和成分以及与块体性能的可能关系的研究。晶界几何形状用五个独立的参数来描述；一般来说，它们的结构宽度在0.4-1.2 nm之间，通常使用的1 nm似乎是一个很好的近似值。这一增强无序的区域通常富含在完美晶格中不相容的元素。晶界的化学成分取决于块状岩石的成分。我们测定了多晶FO的5参数晶界特征分布(GBCD)，并在纳米尺度上研究了结构和化学，扩展了以前的测量结果。我们发现，与晶体c方向垂直的晶界平面主导着晶界网络。我们的结论是，通过EBSD作图和统计分析的GBCD测定，现在可以将整个几何参数空间中的晶界结构与块体岩石性质的变化联系起来。
Interfaces in rocks, especially grain boundaries in olivine dominated rocks, have been subject to about 40 years of studies. The grain boundary structure to property relation is fundamental to understand the diverging properties of polycrystalline samples compared to those of single crystals. The number of direct structural observations is small, i.e. in range of 100 micrographs, and the number of measurements of properties directly linked to structural observations is even smaller. Bulk aggregate properties, such as seismic attenuation, rheology and electrical conductivity, are sensitive to grain size, and seem to show influences by grain boundary character distributions. In this context we review previous studies on grain boundary structure and composition and plausible relations to bulk properties. The grain boundary geometry is described using five independent parameters; generally, their structural width ranges between 0.4–1.2 nm and the commonly used 1 nm seems a good approximation. This region of enhanced disorder is often enriched in elements that are incompatible in the perfect crystal lattice. The chemical composition of grain boundaries depends on the bulk rock composition. We determined the 5 parameter grain boundary character distribution (GBCD) for polycrystaline Foand studied structure and chemistry at the nm-scale to extend previous measurements. We find that grain boundary planes close to perpendicular to the crystallographic c-direction dominate the grain boundary network. We conclude that linking grain boundary structure in its full geometric parameter space to variations of bulk rock properties is now possible by GBCD determination using EBSD mapping and statistical analyses.