Mechanisms of metamorphic microstructure formation

变质微观结构形成机制

• 批准号: RGPIN-2020-04955
• 负责人: Gaidies, Fred
• 金额: $ 1.82万
• 依托单位: Carleton University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=717049
• 关键词: Mechanisms; metamorphic; microstructure; formation

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.

变质岩的微观结构定义了其所含颗粒的尺寸、形状和丰度的三维微观分布，以及分隔它们的晶界网络的空间排列。因此，它对地球地壳的一些最基本的性质产生了重大影响，包括它传播地震波的方式，或构造过程造成的热异常的消散。然而，岩石微结构的起源是变质岩石学中最不了解的方面之一，但众所周知，微结构是基本的亚微观过程的结果，并提供了对基本的亚微观过程机制的直接洞察，例如晶体之间的化学扩散引起的质量传递以及晶体界面处的分子附着和分离，它们的驱动力，以及岩石在其操作期间经历的不平衡程度。 这项研究将有助于更好地理解变质微结构的形成，并有助于解开与变质作用相关的关键过程的岩石成因记录。高分辨率X射线显微计算机断层扫描在申请人的实验室是必不可少的这项研究，并将系统地集成与元素，同位素，地质年代学和晶体学数据集的天然样品，以量化的空间和时间范围的化学和机械不平衡的变质反应和微观结构演变的驱动程序。 研究的一个重要重点将是动力学和分子机制的扩散通量跨多晶聚集体以及矿物界面的物理-化学性质及其对晶体生长的影响，帮助重建的时间尺度和速率的变质过程。此外，还将在基本的成岩作用和大规模的构造作用之间建立联系，如在山带形成期间的陆-陆碰撞或岩石圈减薄。 这项研究将提高加拿大地球科学部门的竞争力，促进公众对矿物和岩石及其形成方式的内在兴趣。直接申请将提供与构成加拿大经济重要部分的资源开采业的联系。