Deformation‐induced microstructures, paleopiezometers, and differential stresses in deeply eroded fault zones
Deformation‐induced microstructures, paleopiezometers, and differential stresses in deeply eroded fault zones
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深度侵蚀断层带中变形引起的微观结构、古水压计和差异应力
DOI：
10.1029/jb085ib11p06269
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发表时间：
1980
影响因子：
--
通讯作者：
M. S. Weathers
中科院分区：
文献类型：
--
作者：
D. Kohlstedt;M. S. Weathers
变形引起的位错密度，亚晶粒大小，并在岩石中的粒度从深侵蚀断层带提供了估计的差异应力时存在的断层活动。实验室实验表明，位错密度，亚晶粒尺寸和晶粒尺寸在稳态变形过程中产生的主要取决于所施加的差应力的大小;温度只有很小的影响，这三个数量通过材料参数，如剪切模量。理论论据支持这些实验结果。根据经验应力-显微结构关系确定的断裂带的差应力在40-200 MPa之间。在许多断层带，如苏格兰的莫因逆冲断层带，可以观察到变形引起的显微结构的逐步发展，特别是在石英岩中。在远离断层面处，石英颗粒几乎等长，但呈波动消光。当接近断层的中心部分时，消光仍然是波动的，因为颗粒变得越来越长（长宽比为100∶1是常见的）和重结晶。在断层带中心附近，石英岩经常100%重结晶。显微结构的这种渐进发展表明，在低应力或零应力下的恢复并没有消除塑性变形机制中最后一次构造事件的信息。
Deformation-induced dislocation densities, subgrain sizes, and grain sizes in rocks from deeply eroded fault zones provide estimates of the differential stresses that existed when the faults were active. Laboratory experiments have demonstrated that the dislocation density, subgrain size, and grain size generated during steady state deformation depend primarily on the magnitude of the applied differential stress; temperature has only a minor influence on these three quantities through materials parameters such as the shear modulus. Theoretical arguments support these experimental results. Differential stresses in fault zones, determined from the empirical stress-microstructure relations, lie in the range 40–200 MPa. In many fault zones, such as the Moine thrust zone in Scotland, the progressive development of the deformation-induced microstructure can be observed, particularly in quartzites. Far from the fault surface, quartz grains are nearly equant but show undulatory extinction. As the central portion of the fault is approached, extinction remains undulatory as the grains become increasingly elongated (aspect ratios of 100∶1 are common) and recrystallized. Quartzites are often 100% recrystallized near the centers of fault zones. This progressive development of the microstructure indicates that recovery at low or zero stress has not erased information on the last tectonic event in the plastic deformation regime.