Effect of strain geometry on the petrophysical properties of plastically deformed aggregates: experiments on Solnhofen limestone
Effect of strain geometry on the petrophysical properties of plastically deformed aggregates: experiments on Solnhofen limestone
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应变几何形状对塑性变形骨料岩石物理性质的影响：Solnhofen 石灰石实验
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
E. Rutter
中科院分区：
文献类型：
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作者：
S. Llana;E. Rutter
摘要采用拉伸、扭转、直剪和轴对称缩短四种实验构型，在方解石塑性变形条件下，对Solnhofen石灰岩试件进行了变形试验。所有实验都在相同的温度(600°C)、围压(200Mpa)和可比应变速率(c.10−4 S−1)的干燥试件上进行。不同的实验环境和一些试件内变形的不均匀提供了很大范围的应变几何形状。它们允许局部施加的应变几何与方解石的晶体择优取向(CPO)模式和方解石颗粒的形状组构的取向相关。用扫描电子显微镜的电子背散射衍射仪(EBSD)测量了方解石中的CPO。在晶体内塑性主导下的变形过程中，CPO的发展包含了关于三维岩石中累积的应变几何的信息，尽管在自然界中可以通过动态再结晶来修改应变几何，这在实验中是看不到的。不同的CPO模式对变形集料的速度结构有显著影响。由CPO推断的地震特征表明，最快的VP波的方向与主应变方向一致，在不同的应变几何形状下，主应变方向不同。
Abstract Specimens of Solnhofen limestone were deformed under conditions where calcite deforms plastically using four experimental configurations: extension, torsion, direct shear and axisymmetric shortening. All experiments were run on dry specimens at the same temperature (600 °C), confining pressure (200 MPa) and comparable strain rates (c. 10−4 s−1). The different experimental settings and the heterogeneity of deformation within some of the specimens provided a large range of strain geometries. They allowed locally imposed strain geometries to be related to the crystallographic preferred orientation (CPO) patterns of calcite and the orientation of the shape fabric of calcite grains. CPO in calcite was measured using electron back-scattered diffraction (EBSD) in scanning electron microscopy. The development of CPO during deformation under the dominance of intracrystalline plasticity contains information about the strain geometry accumulated in rocks in 3D, although in nature the strain geometry can be modified by dynamic recrystallization that was not seen in the experiments. The different CPO patterns have a significant effect on the velocity structure of the deformed aggregates. Seismic properties inferred from CPO show that the orientation of the fastest Vp wave aligns with principal strain directions that are not equivalent in different strain geometries.