Coupled Deformation and Metamorphism, Fabric Development, Rheological Evolution and Strain Localization

当地球的构造板块相互作用时，构成它们的岩石会变形，通常会形成巨大的山链。在这种变形过程中，构成岩石的矿物可以在空间上或晶体上排列，形成一种组构。岩石组构的发育是影响变形岩石强度或流变演化的主要因素。织物的开发通常涉及物理和化学过程的耦合。例如，褶皱解理是多变形岩石中最常见的组构类型，它的形成导致了极端的矿物分离和流变各向异性。它也通常与大型变质矿物(斑岩)的生长有关，构造地质学家利用这些矿物来推断变形历史和力学参数，如剪切应变、剪切应变率和涡度。尽管褶皱劈理在世界各地的山脉中很常见，并可能在一系列尺度上的变形局部化中发挥重要作用，但它的形成细节及其可能的力学意义仍然知之甚少。研究人员和他们的学生正在将基于现场和实验室的研究与计算机建模相结合，以解决岩石组构，特别是褶皱解理对岩石流变演化的影响。选定的田地位于缅因州西部的阿巴拉契亚山脉。该项目的成果将纳入以网络为基础的教育单元，作为各级地球科学教师和学生的资源。

When Earth's tectonic plates interact with one another the rocks that comprise them are deformed, commonly forming great mountain chains. During this deformation, the minerals that make up the rocks can become spatially or crystallographically aligned to form a fabric. The development of rock fabric is a primary factor affecting the strength, or rheological evolution of deforming rocks. Fabric development commonly involves coupling of both physical and chemical processes. For example, crenulation cleavage is the most common type of fabric in multiply deformed rocks, and its formation leads to extreme mineral segregation and rheological anisotropy. It is also commonly associated with the growth of large metamorphic minerals (porphyroblasts), which are used by structural geologists to infer deformation histories and mechanical quantities such as shear strain, shear strain rate and vorticity. Although crenulation cleavage is common throughout the world's mountain chains, and may play an important role in the localization of deformation across a range of scales, the details of its formation, and its possible mechanical significance, remain poorly understood. The investigators and their students are combining field- and laboratory-based studies with computer modeling to address the effects of rock fabric, particularly crenulation cleavage, on the rheological evolution of rocks. The chosen field area is located in the Appalachian mountains of western Maine. The results of this project will be incorporated into web-based educational modules that are intended as resources for earth-science teachers and students at all levels.