High temperature metamorphic processes in large orogens

大陆山带(造山带)是在板块碰撞过程中产生的，是地球表面的一个基本特征，是地壳循环利用的主要场所。我的研究计划的长期目标是利用我在变质岩石学方面的专业知识，更好地了解山脉带的地壳演化。现代变质岩石学的一个主要方向是利用矿物中编码的信息，通过评估地壳岩石随着时间的推移经历的压力(埋藏深度)和温度的变化(变质P-T-t轨迹)来提供对造山过程的洞察。微观分析和热力学模拟的最新进展使我们能够以前所未有的方式提取变质岩的P-T-t演化信息。然而，由于自然系统的复杂性，这种方法的使用并不是微不足道的，在一些情况下，仍处于实验阶段。变质作用的研究在大型热造山带(LHO)的情况下尤其具有挑战性，在LHO中，中地壳到下地壳在800摄氏度以上的长期停留是部分熔融、地壳流动、造山高原的形成和地球历史上最大的山带系统(如今天的喜马拉雅和西藏)发展的实质性质量重新分配的根源。现代的活动山带提供了造山构造的重要证据，但内部建筑只有在受到侵蚀后才能显现。因此，以前的热地壳现在暴露在被侵蚀的古代造山带的核心区，提供了在山根运行过程的无与伦比的记录。典型的例子是中元古代格伦维尔省，它构成了北美东部的一个主要构造单元，被视为现代喜马拉雅-西藏系统的典范古代类比。这项建议侧重于LHO中的高温(T)过程。它的目的是：(I)通过探索矿物数据、P-T路径和时间之间的联系，提高我们解码造山麻粒岩(高T变质岩)的P-T-t记录的能力；以及(Ii)通过在现代地球动力学模型的框架内，通过解开和解释目前暴露在格伦维尔中部的不同地壳水平的P-T-t特征，深入了解LHO的工作原理。拟议的研究涉及综合使用前卫方法，并对高温变质系统的适用性进行了不同程度的探索。矿物数据和P-T路径之间的联系将通过热力学建模、岩石结构调查和微量元素测温(例如，石英中的钛)来建立。此外，将通过测年高T同位素系统(锆石中的U-Pb，石榴石中的Lu-Hf)，以及根据地球化学特征、生长温度(例如，锆石中的钛)和结构来解释年龄，来评估P-T路径与时间之间的联系。预计结果将：为地球历史上最古老的LHO(格伦维尔)提供地球动力学解释的范例；提高对造山环境中高T地壳过程的一般理解；并测试有希望的前线技术在麻粒岩相岩石解释中的适用性。因此，他们将促进地壳演化领域的知识，并为加拿大地球科学的国际形象做出贡献。拟议的研究涉及对研究生和本科生进行大量培训，使他们掌握与调查地球物质如何通过地质过程变化有关的现代技术，因此，广泛适用于与地球科学有关的工作环境。它还将使学生对地球系统是如何工作的产生更多的全球欣赏。

Continental mountain belts (orogens), produced during the collision of tectonic plates, are a fundamental feature of the Earth’s surface, and constitute major sites in which the Earth’s crust is recycled. The long-term goal of my research program is to develop a better understanding of the crustal evolution in mountain belts using my expertise in metamorphic petrology. A major direction of modern metamorphic petrology is to offer insights on mountain building processes by assessing the changes in pressure (depths of burial) and temperature that crustal rocks experience over time (metamorphic P-T-t paths), using information encoded in their minerals. Recent developments in microanalysis and thermodynamic modeling allow us to retrieve information on the P–T-t evolution of metamorphic rocks in unprecedented ways. However, owing to the complexity of natural systems, the use of such approaches is non trivial and, in several instances, still at the experimental stage. Metamorphic studies are particularly challenging in the case of large hot orogens (LHOs), in which protracted residence of the middle to lower crust at temperatures above 800ºC is at the origin of substantial mass redistribution by partial melting, crustal flow, formation of orogenic plateaux and the development of the largest mountain belt systems in Earth’s history (e.g. present day Himalayas and Tibet). Modern, active mountain belts offer vital evidence of orogenic structure, but the internal architecture is only revealed after erosion. Therefore, formerly hot crust presently exposed in the core zones of eroded ancient orogens, provides an unparalleled record of processes operating at the mountain roots. The type example is the Mesoproterozoic Grenville Province, which constitutes a major tectonic element in eastern North America and is viewed as the exemplary ancient analogue to the modern Himalaya-Tibet system. This proposal focuses on high temperature (T) processes in LHOs. It aims to: (I) improve our ability to decode the P–T –t record of orogenic granulites (high-T metamorphic rocks) by exploring links between mineral data, P–T paths and time; and (II) provide insight into how LHOs work, by unraveling and interpreting the P–T–t signatures of contrasting crustal levels presently exposed in the central Grenville, within the framework of modern geodynamic models. The proposed research involves integrated use of avant-garde approaches with variably explored applicability to high-T metamorphic systems. Links between mineral data and P–T paths will be established by means of thermodynamic modeling, investigation of rock textures, and trace element thermometry (e.g. Ti-in-quartz). In addition, links between P–T paths and time will be assessed by dating high-T isotopic systems (U-Pb in zircon, Lu-Hf in garnet), and by interpreting the ages in the context of geochemical signatures, temperatures of growth (e.g. Ti-in-zircon) and textures. The results are expected to: provide a paradigm for the geodynamic interpretation of the oldest LHO in Earth’s history (Grenville); improve understanding of high-T crustal processes in orogenic settings in general; and test the applicability of promising front line techniques on the interpretation of granulite facies rocks. Therefore, they will advance knowledge in the field of crustal evolution, and contribute to the international profile of Canadian geosciences. The proposed research involves substantial training of graduate and undergraduate students in modern techniques relevant to investigation of how Earth materials change through geological processes, and therefore, with wide applicability to Earth Science-related work environments. It will also allow students to develop a more global appreciation of how Earth systems work.