A kinetic model of oriented nucleation under nonhydrostatic stress: Implications for the preferred orientation of columnar and platy minerals in metamorphic rocks
A kinetic model of oriented nucleation under nonhydrostatic stress: Implications for the preferred orientation of columnar and platy minerals in metamorphic rocks
复制标题
非静水应力下定向成核的动力学模型：对变质岩中柱状和板状矿物择优取向的影响
DOI：
10.1016/j.jsg.2020.104275
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发表时间：
2021
影响因子：
3.1
通讯作者：
Omori Yasutomo
中科院分区：
文献类型：
--
作者：
Masuda Toshiaki;Omori Yasutomo
我们提出了非静水应力变质岩中柱状和板状矿物成核速率的动力学模型。在我们的模型中，成核速率I表示为I T， σ n= A exp−Δ U∗−T Δ S∗+ σ n Δ V∗k B T，其中Δ U∗，Δ S∗和Δ V∗分别是内能、熵和活化体积，k B是玻尔兹曼常数，T是绝对温度，σ n是施加在非均相成核部位的正应力的大小，A是常数。在非静水应力岩石中，σ n随成核位置的空间取向而变化，成核速率I也随之变化。由于成核颗粒的数量与成核数量成正比，各向异性成核可以产生矿物颗粒的优先取向。该模型预测了垂直于主应力轴切割的任意平面上柱状矿物颗粒的长轴和极到板状矿物颗粒基面的von Mises分布。该模型还使用拉姆斯应力椭球的指数形式来绘制等高线等面积立体织物图。由于生成的模式与在变质岩中观察到的相似，该模型可能对自然变形的分析有用。
We propose a kinetic model for the nucleation rate of columnar and platy minerals in nonhydrostatically stressed metamorphic rocks. Nucleation rate I in our model is expressed as I T, σ n= A exp− Δ U∗− T Δ S∗+ σ n Δ V∗ k B T, Where Δ U∗, Δ S∗ and Δ V∗ are the internal energy, entropy and volume of activation, respectively, k B is the Boltzmann constant, T is absolute temperature, σ n is the magnitude of the normal stress applied to the site of heterogeneous nucleation, and A is a constant. As σ n varies with respect to the spatial orientation of the nucleation site in nonhydrostatically stressed rocks, the nucleation rate I also varies accordingly. As the number of nucleated grains is proportional to I, anisotropic nucleation can produce a preferred orientation of mineral grains. The model predicts the von Mises distributions of the long axes of columnar mineral grains and poles to the basal planes of platy mineral grains on any plane cut perpendicular to the principal-stress axes. The model also uses the exponential form of the Lamé’s stress ellipsoid to plot contoured equal-area stereographic fabric diagrams. As the generated patterns are similar to those observed in metamorphic rocks, the model is likely useful for analyses of natural deformation.