Diffusion Flow Laws in Metamorphic Rocks
Diffusion Flow Laws in Metamorphic Rocks
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变质岩中的扩散流定律
DOI：
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发表时间：
1973
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影响因子：
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通讯作者：
D. Elliott
中科院分区：
文献类型：
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作者：
D. Elliott
压力溶解变形的岩石服从线性粘性或牛顿应力-应变率关系的扩散流动定律。原始晶粒的未变形文物保存在新生长的晶体在晶界张力和presolved表面下，在压缩下的晶界上的惰性粒子的积累一起，是诊断的扩散流动规律的证据。在一定的应力下，应变速率与晶粒尺寸成2或3次方的反比。地质学上有用的曲线以温度与粒度对数的倒数作为坐标。这样一个图形被分成三个边界，满足在一个三重点领域;在每个领域内，无论是晶格扩散，晶界扩散，或位错流动法是占主导地位的。也许可以用自然变形的岩石来校准这张图。马里兰州南山-蓝岭地区等斜褶皱绿片岩级石英岩和流纹岩流的显微照片显示了扩散传质变形机制，但与目前可用的实验室扩散数据相比，有效扩散系数的估计不足以确定扩散路径。然而，相对较低的变质温度与熔融温度的比值和晶界的物理性质，特别是低密度杂质在晶界上的浓度，建议晶界扩散流动规律。
Rocks which deform by pressure solution obey a diffusion flow law with a linear viscous or Newtonian stress to strain-rate relation. Undeformed relics of original grains preserved within newly grown crystals at grain boundaries under tension and presolved surfaces, together with accumulation of inert particles at grain boundaries under compression, are diagnostic evidence of a diffusion flow law. At a given stress, strain-rate is inversely proportional to the grain size to a power of two or three. A geologically useful plot has inverse temperature versus the logarithm of grain size as coordinates. Such a graph is separated into fields by three boundaries which meet at a triple point; within each field, either lattice diffusion, grain-boundary diffusion, or a dislocation flow law is predominant. It may be possible to calibrate this graph from naturally deformed rocks. Photomicrographs of isoclinally folded greenschist-grade quartzites and rhyolitic flows from the South Mountain–Blue Ridge area in Maryland demonstrate a diffusive mass transfer deformation mechanism, but estimates of effective diffusion coefficient compared to currently available laboratory diffusion data are insufficient to identify the diffusion path with certainty. However, the comparatively low ratio of metamorphic temperature to melting temperature and the physical nature of grain boundaries in metamorphic rocks, particularly concentrations of low-density impurities at grain boundaries, suggest the grain-boundary diffusion flow law.