A new method to track the evolution of rock microstructures in shear deformation (torsion) experiments.

岩石微结构在蠕变变形过程中不断演化，对岩石的蠕变机制和流变特性具有根本控制作用。如果我们能够在实验过程中跟踪单个晶粒和晶界的演变，那么对蠕变变形的理解将大大提高。与地壳或上地幔有关的多晶材料的蠕变实验还没有成功地跟踪单个颗粒的显微结构演化。该提案旨在开发和测试一种新的、相对简单和廉价的方法，以跟踪在实验室蠕变实验期间特定岩石微观结构（例如单个颗粒）在升高的压力（P）和温度（T）下的高剪切应变的演变;该方法适用于广泛的岩石类型。在支持的情况下，我们证明了一个单一的圆柱形样品可以在扭转和每个应变增量之间成像的圆柱体的外表面上的微观结构的扭转增量。该提案要求为扫描电子显微镜（SEM）的一个阶段提供资金，该阶段将能够1）在没有扭曲的情况下对圆柱形样品的外表面进行微观结构测绘，2）准确记录不同应变增量的数据。一个试点研究，剪切卡拉拉大理石，将跟踪单个晶粒的取向和内部结构，晶界的迁移，再结晶晶粒的取向和演变，并应提供新的见解多晶变形和再结晶。

Rock microstructures evolve during creep deformation and have a fundamental control on creep mechanisms and rheology. Understanding of creep deformation would improve significantly if we could track the evolution of individual grains and grain boundaries during experiments. No creep deformation experiments of polycrystalline materials relevant to the crust or upper mantle have succeeded in tracking the microstructural evolution of individual grains. This proposal aims to develop and test a new, relatively easy and inexpensive method to track the evolution of specific rock microstructures (e.g. individual grains) during laboratory creep experiments to high shear-strain at elevated pressure (P) and temperature (T); a method applicable to a wide range of rock types. In the case for support we demonstrate that a single cylindrical sample can be twisted incrementally in torsion and the microstructures on the outer surface of the cylinder imaged between each strain increment. The proposal requests funding for a stage for a scanning electron microscope (SEM) that will enable 1) microstructural mapping of the outer surface of cylindrical samples without distortions and 2) accurate registration of data from different strain increments. A pilot study, shearing Carrara marble, will track the orientation and internal structure of individual grains, migration of grain boundaries, and the orientation and evolution of recrystallized grains and should give new insights into polycrystal deformation and recrystallization.