Microstructure evolution and grain boundary mobility during creep deformation and annealing of anhydrite rocks.

硬石膏岩石蠕变变形和退火过程中的微观结构演化和晶界迁移率。

基本信息

批准号：
NE/H001034/1
负责人：
Elisabetta Mariani
金额：
$ 9.69万
依托单位：
University of Liverpool
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FH001034%2F1
关键词：
Microstructure evolution grain boundary mobility

项目摘要

Anhydrite (CaSO4) is important in the shallow Earth's crust as a detachment horizon in major fault zones at tectonic plate boundaries, cap-rock for hydrocarbon reservoirs, CO2 sequestration, and potential repository for radioactive waste. Also anhydrite is a useful silicate-analogue material and its physical properties are relevant to the rheology and recrystallization of other comparable minerals. Recovery and recrystallization processes occur during plastic deformation (dislocation creep) and annealing (static heating) of materials, through the formation and movement of grain boundaries. In the Earth's crust and mantle syn-tectonic (dynamic) and post-tectonic (static) recrystallization of rocks can modify grain sizes, shapes and crystallographic orientations. This affects physical properties and anisotropies and is central to the interpretation of the mechanical behaviour of rocks in major fault zones along plate boundaries, geological terrains in mountain belts, and seismic anisotropy data. The recrystallization behaviour and relevant boundary properties (geometry, mobility, diffusivity and sliding) of anhydrite and minerals in general, are poorly understood. In minerals characterized by special boundaries such as twin boundaries (anhydrite, calcite, quartz, plagioclase), observed microstructures cannot be explained by sub-grain rotation and boundary migration recrystallization alone and two other mechanisms have been proposed, namely grain boundary sliding, accompanied by diffusion and resulting in material weakening and a recrystallization mechanism accounting for special (twin) boundaries. This occurs during crystal plastic deformation at relatively high stresses. In the final microstructures of naturally and experimentally deformed rocks detailed evidence of microstructural evolution, and the mechanisms that drive it, is often obliterated. Non-standard deformation and annealing laboratory experiments, where anhydrite aggregates will be taken to small increments of strain and time respectively and, after each increment, analysed using EBSD, will be performed to gain insight into 1. The dynamics and kinematics of recrystallization assisted by twin boundaries, 2. The role that this plays in the deformation behaviour of anhydrite aggregates and other comparable minerals. Such tests are non-standard because the same sample, rather than different ones as is conventional in rock deformation tests, will be taken to increments of strain or time and sequentially analysed. This will allow tracking the evolution of individual grains and grain boundaries during creep deformation and annealing of a polycrystalline material. During each deformation experiment the fine mechanical response to specific microstructural changes, will be recorded by the high resolution strain gauges of the deformation apparatus. Quantitative information on boundary geometry, misorientation, grain distortion, kinematics of low and high angle grain boundary migration, grain boundary mobility, the role of twinning, and mechanical response to microstructural change will be achieved. Boundary mobility measured in the creep rig will be compared with the mobility data obtained from direct observation of boundary motion in novel in-situ annealing experiments in the scanning electron microscope, which will be performed on anhydrite as part of this experimental program. The important effect of isostatic pressure on grain boundary mobility will be tested performing high confining pressure experiments and comparing results with those from creep rig tests (room pressure). The evidence thus gathered on recrystallization mechanisms, mobility and mechanical response to microstructural changes of anhydrite polycrystals will be the basis upon which more realistic recrystallization models can be constructed. This will underpin our interpretation of syn- and post-tectonic processes in the Earth's crust and mantle.

硬石石（Caso4）在浅层地壳中作为构造板边界的主要断层区域的脱落地层，碳氢化合物储层的盖岩，二氧化碳蓄电池和潜在放射性废物的潜在存储库。硬石石也是一种有用的硅酸盐 - 动物材料，其物理特性与其他类似矿物的流变学和重结晶有关。通过晶粒边界的形成和运动，材料的塑性变形（位错蠕变）和材料的退火（静态加热）期间发生恢复和重结晶过程。在地球和地幔和地幔中，岩石的结合（动态）和岩石后（静态）重结晶可以改变晶粒尺寸，形状和晶体学方向。这会影响物理特性和各向异性，并且是对沿板边界的主要断层区域中岩石的机械行为的解释，山带的地质地形和地震各向异性数据的核心。一般而言，赤铁矿和矿物质的重结晶行为和相关的边界特性（几何，移动性，扩散性和滑动）一般而言。在以特殊边界为特征的矿物中，例如双边界（赤铁矿，方解石，石英，斜长石），观察到的微观结构不能通过亚细胞旋转和单独的边界迁移再结晶，并且提出了另外两个机制，并提出了另外两个机制，即差异，并伴随着晶状体的弱化，并伴随着晶状体的差异，并伴随着折射的机制。边界。这是在晶体塑性变形时发生的，在相对较高的应力下。在自然和实验变形的岩石的最终微观结构中，微观结构进化的详细证据以及驱动它的机制通常是消失的。非标准的变形和退火实验室实验，在该实验中，硬石组骨料将分别分别达到压力和时间的少量增量，每次增加后，使用EBSD进行分析，将进行1个深入了解1的动力学和动力学，由双胞胎边界的再结晶辅助2。此类测试是非标准化的，因为在岩石变形测试中，相同的样品而不是与常规样本相同的样本，将被带到应变或时间的增量中，并顺序分析。这将允许跟踪多晶材料的蠕变变形和退火过程中单个晶粒和晶界的演变。在每个变形实验中，对特定微观结构变化的精细机械响应将通过变形设备的高分辨率应变测量值记录。关于边界几何，不良差异，晶粒失真，低角度和高角度晶界迁移的运动学，晶界迁移率，孪晶的作用以及对微结构变化的机械响应的定量信息。将在蠕变钻机中测得的边界迁移率与在扫描电子显微镜中新型的现场退火实验中直接观察边界运动获得的迁移率数据进行比较，该实验将作为该实验程序的一部分进行。等层压对晶界迁移率的重要影响将进行测试，以执行高约束压力实验，并将结果与蠕变钻机测试（房间压力）的结果进行比较。因此收集的关于重结晶机制，迁移率和对赤铁矿多晶的微结构变化的机械响应的证据将是可以构建更现实的再结晶模型的基础。这将支持我们对地壳和地幔中的合成过程和后传统过程的解释。