Low Temperature Dynamic Recrystallization: Processes and Rheological Consequences

下地壳和上地幔岩石通常显示出局部的韧性剪切带，其特征是比寄主岩石更细的粒度;这种应变局部化意味着应变弱化过程。伴随位错蠕变的动态再结晶是倾向于减小晶粒尺寸的主要过程，并且已经确定了几种不同的动态再结晶机制;对于石英，这些机制定义了位错蠕变的三个“区域”，具有明显不同的微观结构和机械行为。低温、高应力的晶界鼓出过程在石英和长石中都产生应变弱化和局部化，而高温的亚晶旋转过程则不会。以前对橄榄石的研究主要集中在高温、低应力蠕变上，尽管有迹象表明在较低温度下会发生膨胀再结晶和应变局部化。该项目的目标是量化石英中膨胀重结晶的本构行为和压力计关系，以及橄榄石验证此过程的存在，确定其操作的条件，并量化其产生的应变弱化。这些结果应该可以更准确地模拟岩石圈变形。

EAR-0208150Jan TullisLower crustal and upper mantle rocks commonly show localized ductile shear zones, characterized by a finer grain size than the host rocks; such strain localization implies a strain weakening process. Dynamic recrystallization accompanying dislocation creep is a major process tending to reduce grain size, and several distinct mechanisms of dynamic recrystallization have been identified; for quartz these define three 'regimes' of dislocation creep, with distinctly different microstructures as well as mechanical behavior. The low temperature, higher stress process of grain boundary bulging produces strain weakening and localization in both quartz and feldspar, whereas the higher temperature process of subgrain rotation does not. Previous work on olivine has focussed on high temperature, low stress creep, although there are indications of bulging recrystallization and strain localization at lower temperatures. The goals of this project are to quantify the constitutive behavior and piezometer relation for bulging recrystallization in quartz, and for olivine to verify the existence of this process, determine the conditions over which it operates, and quantify the strain weakening it produces. The results should allow more accurate modelling of lithospheric deformation.