Electrical impedance measurement of plastically deforming halite rocks at 125°C and 50 MPa -: art. no. 2004
Electrical impedance measurement of plastically deforming halite rocks at 125°C and 50 MPa -: art. no. 2004
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DOI：
10.1029/2001jb000204
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发表时间：
2002-01-10
影响因子：
3.9
通讯作者：
Peach, CJ
中科院分区：
文献类型：
--
作者：
Watanabe, T;Peach, CJ
[1]电阻抗测量已进行变形细粒（类似于300妈妈）合成岩盐岩石含有少量的水，以研究流体分布的演变。在非水化条件下（125 ℃，50 MPa围压，应变速率约为5 × 10（-7）s（-1）），用三轴变形仪对四个湿试样（H2O约为30 ppm）和一个“干”试样（H2O约为5 ppm）进行了实验。湿态和干态样品的力学行为有着显著的不同。只有30 ppm的水通过晶界迁移重结晶大大削弱了岩盐岩。湿态实验显示振荡的应力-应变曲线，反映了由于动态再结晶的加工硬化和弱化之间的竞争。干态实验表明，既没有弱化，也没有再结晶组织。测量的阻抗表明，即使在干燥样品中也形成了水的互连网络，并且通过非常薄的（1-10 nm）流体元素获得了本体的连通性。电阻率随形变的变化表明连通流体通道的变薄和变厚之间存在竞争。变薄是由于轴向压缩引起的流体喷射引起的，而增厚是由于流体辅助晶界迁移引起的晶粒生长引起的流体喷射引起的。在湿样品中，通过晶界水的扩散系数估计比本体水低5-6个数量级。在干燥样品中，晶界水较薄，其扩散率可能不足以促进晶界迁移。所观察到的迁移重结晶可以在自然条件下发生，并大大削弱盐岩。阻抗测量对于跟踪变形材料中流体分布的演变是非常有用的。为了进一步了解岩盐岩石的力学和电学性质，有必要阐明薄水膜的性质。
[1] Electrical impedance measurements have been performed on deforming fine-grained (similar to300 mum) synthetic halite rocks containing small quantities of water in order to study the evolution of fluid distribution. Experiments were carried out on four wet samples (H2O similar to 30 ppm) and one "dry'' sample (H2O similar to 5 ppm) under nondilatant condition (125 degreesC, 50 MPa confining pressure, and strain rate of similar to5 x 10(-7) s(-1)), using a triaxial deformation apparatus. The mechanical behavior of wet and dry samples is strikingly different. Only 30 ppm water greatly weakens halite rocks through grain boundary migration recrystallization. Wet experiments show oscillating stress-strain curves, reflecting the competition between work hardening and weakening due to dynamic recrystallization. The dry experiment shows neither weakening nor recrystallized microstructure. The measured impedance shows that an interconnected network of water is formed even in the dry sample and that the connectivity in bulk is attained through the very thin (1-10 nm) elements of fluid. The resistivity change with deformation suggests the competition between thinning and thickening of connected fluid paths. The thinning is caused by fluid squirt due to the axial compression, and the thickening is caused by fluid squirt due to the grain growth due to fluid-assisted grain boundary migration. In wet samples the diffusivity through grain boundary water is estimated to be lower than the bulk water by 5-6 orders of magnitude. In the dry sample, grain boundary water is thinner, and its diffusivity might not be high enough to promote grain boundary migration. Observed migration recrystallization can occur in natural conditions and greatly weaken salt rocks. The impedance measurement is very useful to track the evolution of fluid distribution in deforming materials. For further understanding of mechanical and electrical properties of halite rocks it is essential to clarify properties of thin water films.