Conditions, rates and mechanisms of fundamental metamorphic processes

岩石纹理和微观结构的起源是变质岩石学中最不为人所知的方面之一。然而众所周知，它极大地影响着地壳的一些最基本的特性，例如地壳在塑性变形过程中的行为、传播地震波的方式，或者响应构造过程而形成和消散的热异常的速率。需要资助研究，这将使人们对控制岩石纹理和微观结构形成的基本过程的理解达到一个新的水平。这项研究将详细的岩相学和地质年代学研究与平衡和动力学模型结合起来，以量化这些基本过程的速率、压力、温度和化学条件，包括成核、晶体生长、扩散和矿物溶解。***过去，采用化学平衡方法来估计岩石形成的条件。然而，申请人和同事最近的研究提出了一个问题：岩石形成过程所需的不平衡是否可能比之前假设的更大，这将对岩石形成条件的估计方式以及如何解释这些估计产生重要影响。拟议研究的一个特别重点是量化变质过程所需的化学平衡偏离，以及这如何取决于界面和应变能以及定向应力和变质矿物反应动力学的相互作用。这项研究将有助于评估和开发对重要构造过程的新约束，从山带形成的性质和速率到地球中地壳半粘性岩石的流动机制。***该研究要解决的主要问题是：（1）影响岩石纹理和微观结构形成的关键参数的数量级是多少？ （2）这些关键参数之间有何关系？它们如何依赖于地质过程中变质环境的变化？ (3)这些参数与岩石微观结构和大范围构造过程之间有何联系？对岩石微观结构形成关键参数的相互作用和大小的研究仍处于起步阶段，但需要增进我们对化学反应动力学在地质系统中的作用的理解。拟议的研究将提高加拿大地球科学部门的竞争力，有助于激发公众对矿物和岩石及其形成方式的内在兴趣。该研究的直接应用将提供与构成加拿大经济重要组成部分的资源开采行业的联系。 **

The origin of rock texture and microstructure is one of the least understood aspects of metamorphic petrology. Yet it is known that it drastically influences some of the most elemental properties of Earth's crust such as its behavior during plastic deformation, the way it transmits seismic waves, or the rate with which thermal anomalies form and dissipate in response to tectonic processes. Funding is requested for research that will lead to a new level of understanding of the fundamental processes that govern the formation of rock texture and microstructure. This research will integrate detailed petrographic and geochronological investigations with equilibrium and kinetic modelling to quantify the rates and pressure, temperature and chemical conditions of these fundamental processes that include nucleation, crystal growth, diffusion and mineral dissolution.***In the past, an approach to chemical equilibrium was utilized to estimate the conditions of rock formation. However, recent research by the applicant and coworkers induced the question whether the disequilibrium required for rock-forming processes may be larger than previously assumed which would have important implications for the way rock-forming conditions are estimated and how these estimates are interpreted. A particular focus of the proposed research will be to quantify the departure from chemical equilibrium required for metamorphic processes, and how this depends on the interplay of interface and strain energy and directed stress and metamorphic mineral reaction kinetics. This research will help to evaluate and develop new constraints on important tectonic processes ranging from the nature and rates of mountain belt formation to the mechanisms of flow of semi-viscous rocks in Earth's mid-crust.***Major questions to be addressed by the research are: (1) What is the order of magnitude of the key parameters that impact on rock texture and microstructure formation? (2) How are these key parameters related to each other and how do they depend on changes of the metamorphic environment during geological processes? (3) What is the link between these parameters, rock microstructure, and large-scale tectonic processes? Research on the interplay and magnitudes of the key parameters for rock microstructure formation is still in its infancy but required to advance our understanding of the role of chemical reaction kinetics in geological systems. The proposed research will increase the competitiveness of Canada's earth science sector contributing to public's intrinsic interest in minerals and rocks and how they form. Direct applications of that research will provide links to the resource extraction industries which form an important segment of the Canadian economy.**