Low Temperature Dynamic Recrystallization: Processes and Rheological Consequences

下地壳和上地幔岩石通常表现出局部韧性剪切带，其特征是比宿主岩石粒度更细；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减小晶粒尺寸的主要过程，目前已经确定了几种不同的动态再结晶机制；对于石英，这些定义了三种位错蠕变“制度”，具有明显不同的微观结构和力学行为。晶界胀形的低温、高应力过程在石英和长石中均产生应变弱化和局部化，而亚晶旋转的高温过程则不会产生应变弱化和局部化。尽管有迹象表明橄榄石在较低温度下会出现胀形再结晶和应变局部化，但先前对橄榄石的研究主要集中在高温、低应力蠕变方面。该项目的目标是量化石英中胀形再结晶的本构行为和压电关系，并对橄榄石验证这一过程的存在，确定其运行的条件，并量化其产生的应变减弱。这些结果应该可以更精确地模拟岩石圈的变形。

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.