Deciphering the metamorphic record of orogenic belts

破译造山带的变质记录

• 批准号: RGPIN-2019-05653
• 负责人: Indares, Aphrodite
• 金额: $ 2.62万
• 依托单位: Memorial University of Newfoundland
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=738430
• 关键词: Deciphering; metamorphic; record; orogenic; belts

For most of the Earth's history the evolution of continental crust is marked by the formation and breakup of supercontinents, which are assembled through collision of tectonic plates and development of mountain belts (orogens). In these settings, continental crust is progressively buried and heated up, leading to changes (metamorphism) in the rocks involved. The long-term goal of my research program is to advance understanding of crustal evolution in mountain belts using my expertise in metamorphism. Changes in pressure and temperature over time (P-T-t paths) during orogeny are encoded in mineral assemblages, and this record can be revealed in unprecedented ways due to recent developments in microanalysis and thermodynamic modeling. However, in complex natural systems, this task is non-trivial and is partly at an exploratory stage. Metamorphic studies are particularly challenging in the case of large hot orogens (LHOs), where long residence of middle to lower crust at T > 800ºC results in partial melting and crustal flow, rise of orogenic plateaux and the development of the largest orogens in Earth's history (ex. present-day Himalayas-Tibet). Modern mountain belts offer vital evidence of orogenic structure, but the internal architecture is only revealed after erosion. Hence, exposed core zones of eroded ancient orogens provide key record of processes at mountain roots. A classic example is the Mesoproterozoic Grenville Province, which forms a major tectonic element in eastern North America and is viewed as an ancient analogue to the modern Himalaya-Tibet system. This proposal focuses on high-T processes in LHOs. It aims to decode the P-T-t record of granulites (high-T metamorphic rocks) from the Grenville Province, by exploring links between minerals, P-T paths and time. Mineral textures will be assessed by sophisticated imaging techniques, and P-T paths will be inferred by thermodynamic modelling of mafic granulites, an informative rock type for which models have only become available 2 years ago. The time dimension will be added by dating high-T isotopic systems  in monazite, zircon and  garnet, with a combination of methods rarely used at the scale of a single rock, and by integrating ages with geochemical signatures, T of growth and textures. The results will shed light on the evolution of the Earth's crust with time, by providing a paradigm for the geodynamic interpretation of the oldest LHO in Earth's history, improving insight on high-T orogenic processes in general, and testing cutting-edge approaches in metamorphic petrology. The proposed research involves substantial training of graduate and undergraduate students in modern analytical, imaging and modeling techniques relevant to investigation of how Earth materials change through geological processes, with wide applications to Earth Science-related work environments, and will promote development of a more global appreciation of how Earth systems work.

在地球历史的大部分时间里，大陆地壳的演化以超级大陆的形成和分裂为标志，超级大陆是通过构造板块的碰撞和山脉带（造山带）的发展而聚集起来的。在这些环境中，大陆地壳逐渐被掩埋和加热，导致岩石发生变化（变质作用）。我的研究计划的长期目标是利用我在变质作用方面的专业知识来促进对山区地壳演化的理解。 地壳运动期间压力和温度随时间的变化（P-T-t路径）被编码在矿物组合中，由于微观分析和热力学建模的最新发展，这种记录可以以前所未有的方式被揭示。然而，在复杂的自然系统中，这项任务是不平凡的，部分处于探索阶段。变质作用研究在大型热造山带（LHO）的情况下特别具有挑战性，在那里，中地壳到下地壳在T > 800ºC的长期居住导致部分熔融和地壳流动，造山高原的上升和地球历史上最大造山带的发展（例如。今喜马拉雅-西藏）。现代山脉为造山构造提供了重要的证据，但内部结构只有在侵蚀后才能显露出来。因此，暴露的核心地带的侵蚀古造山带提供了关键的记录过程中的山根。一个典型的例子是中元古代的格伦维尔省，它形成了北美东部的一个主要构造单元，被视为现代喜马拉雅-西藏系统的古代类似物。 该提案侧重于LHO中的高温过程。它旨在通过探索矿物、P-T路径和时间之间的联系，解码格伦维尔省麻粒岩（高温变质岩）的P-T-t记录。矿物结构将通过复杂的成像技术进行评估，P-T路径将通过镁铁质麻粒岩的热力学建模进行推断，镁铁质麻粒岩是一种信息丰富的岩石类型，其模型仅在2年前可用。时间维度将通过独居石、锆石和石榴石中的高T同位素系统测年来增加，结合很少在单一岩石规模上使用的方法，并通过将年龄与地球化学特征、生长和结构的T相结合来增加。 研究结果将揭示地壳随时间的演化，为地球历史上最古老的LHO的地球动力学解释提供一个范例，提高对高温造山过程的认识，并测试变质岩石学的尖端方法。拟议的研究涉及对研究生和本科生进行现代分析，成像和建模技术的大量培训，这些技术与地球材料如何通过地质过程变化的调查有关，广泛应用于地球科学相关的工作环境，并将促进对地球系统如何工作的更全面的了解。