Kinetics of garnet nucleation and growth during metamorphism

提出的研究旨在定量了解岩石形成过程中的两个基本过程：成核和晶体生长。将研究这些过程的速率和机制，并研究它们对岩石矿物含量的大小、空间分布和化学组成的影响。岩石中所有矿物颗粒的大小和形状以及它们之间的相互关系决定了岩石的质地。我的研究将为纹理形成的性质和速率提供新的见解。这一点很重要，因为岩石的结构从根本上决定了岩石的整体特性，如导电性、强度和固体地球对外力变化的反应方式。人们对控制岩石结构形成的机制知之甚少，需要有新的发现。我的主要研究重点将是岩石变质过程中石榴石的结晶。选择石榴石是因为它的化学成分反映了结晶过程中地壳中普遍存在的压力(P)和温度(T)条件。它还允许确定P和T随时间变化的速率。这些信息对于理解山带的构造演化是至关重要的。将开发模拟石榴石结晶的数值模型，并根据岩石中观察到的矿物化学和纹理进行校准。在变质作用期间化学平衡速率的量化方面将取得进展。这是正确解释如此多构造解释所依赖的矿物分带和矿物组合所必需的。所要求的经费用于实地工作、分析研究的有关费用以及支助研究生和本科生。学生的指导与训练是本研究的一个重要目标。除了深入了解岩石演化的基本过程外，学生还将获得研究项目开发、研究成果交流以及最先进的分析和计算技术应用方面的经验。

The proposed research aims at a quantitative understanding of two fundamental processes during rock formation: nucleation and crystal growth. The rates and mechanisms of these processes will be investigated and their influences on the size and spatial distribution and chemical composition of the mineral content of rocks will be studied. The sizes and shapes of all the mineral grains in a rock and their mutual interrelationships define the texture of the rock. My research will provide new insights into the nature and rates of texture formation. This is important since rock-texture fundamentally contributes to bulk rock properties such as electrical conductivity, strength and the way solid Earth responds to changes in external forces. Only little is known about the mechanisms that control rock-texture formation and novel findings are required. A major focus of my research will be on the crystallization of garnet during rock metamorphism. Garnet is chosen because its chemical composition reflects the pressure (P) and temperature (T) conditions that prevailed in the Earth's crust during crystallization. It also allows for the determination of the rates with which P and T changed through time. This information is fundamental for an understanding of the tectonic evolution of mountain belts. Numerical models that simulate garnet crystallization will be developed and calibrated with mineral chemistries and textures observed in rocks. Progress will be made on the quantification of the rates of chemical equilibration during metamorphism. This is needed to correctly interpret mineral zoning and mineral assemblages on which so much tectonic interpretation depends. Funds are requested for field work, related costs for analytical studies and for the support of graduate and undergraduate students. Mentoring and training of students is an essential target of this research. Besides a deep understanding of fundamental processes during rock evolution, students will gain experience in the development of a research program, the communication of research results, and the application of state-of-the-art analytical and computational techniques.