Mechanisms of metamorphic microstructure formation

变质岩的微结构定义了其所含颗粒的大小、形状和丰度的三维微观分布，以及分隔它们的颗粒边界网络的空间排列。因此，它极大地影响了地球地壳的一些最基本的性质，包括它传播地震波的方式，或由构造过程产生的热异常的消散。然而，岩石微结构的起源是变质岩石学中最不被了解的方面之一，但众所周知，这种微结构是基本的、亚微观过程的结果，并提供了直接的洞察机制，例如通过晶体之间的化学扩散进行的质量传递，以及晶体界面上的分子附着和分离，它们的驱动力，以及岩石在操作过程中经历的不平衡程度。这项研究将有助于更好地了解变质微结构的形成，并将有助于解锁与变质作用有关的关键过程的岩石成因记录。申请人实验室提供的高分辨率X射线微型计算机断层扫描对这项研究至关重要，将与自然样品的元素、同位素、地质年代学和结晶学数据集系统地整合，以量化作为变质反应和微结构演变驱动因素的化学和机械不平衡的空间和时间程度。研究的重点将是多晶集合体中扩散通量的动力学和分子机制，以及矿物界面的物理化学性质及其对晶体生长的影响，有助于重建变质过程的时间尺度和速率。此外，将在基本的岩石形成过程和大规模的构造过程之间建立联系，例如在山脉带形成期间的大陆-大陆碰撞或岩石圈变薄。这项研究将提高加拿大地球科学部门的竞争力，有助于提高公众对矿物和岩石及其形成方式的内在兴趣。直接申请将提供与资源开采行业的联系，这些行业构成加拿大经济的一个重要部分。

The microstructure of a metamorphic rock defines the three-dimensional microscopic distribution of the sizes, shapes, and abundances of the grains it contains, and the spatial arrangement of the grain boundary network separating them. It therefore significantly influences some of the most elemental properties of our planet's crust, including the way it transmits seismic waves, or the dissipation of thermal anomalies resulting from tectonic processes. However, the origin of rock microstructure is one of the least understood aspects of metamorphic petrology but it is known that the microstructure is a result of and provides direct insight into the mechanisms of fundamental, sub-microscopic processes such as mass transfer by chemical diffusion between crystals as well as molecular attachment and detachment at crystal interfaces, their driving forces, and the extent of disequilibrium experienced by the rock during their operations. The proposed research will result in a better understanding of metamorphic microstructure formation and will help to unlock the petrogenetic record of key processes associated with metamorphism. High-resolution X-ray micro--computed tomography available in the applicant's laboratory is essential for this research and will be systematically integrated with elemental, isotopic, geochronological, and crystallographic datasets of natural samples in order to quantify the spatial and temporal extent of chemical and mechanical disequilibrium as drivers of metamorphic reaction and microstructure evolution. An important focus of the research will be on the kinetics and molecular mechanisms of diffusive fluxes across polycrystalline aggregates as well as the physico--chemical properties of mineral interfaces and their influence on crystal growth aiding in the reconstruction of the timescales and rates of metamorphic processes. Furthermore, links will be established between the fundamental, rock--forming processes and large--scale, tectonic processes such as continent-continent collision during mountain belt formation or the thinning of lithosphere. This research will increase the competitiveness of Canada's earth sciences sector contributing to public's intrinsic interest in minerals and rocks and how they form. Direct applications will provide links to the resource extraction industries which form an important segment of the Canadian economy.