Faults and fluids in accretionary orogens

增生造山带的断层和流体

• 批准号: RGPIN-2021-03318
• 负责人: Kellett, Dawn
• 金额: $ 2.62万
• 依托单位: Saint Mary's University
• 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=742494
• 关键词: Faults; fluids; accretionary; orogens

Accretionary orogens (mountain belts) form over tens to hundreds of millions of years as continental and oceanic fragments (terranes) carried on a subducting oceanic plate accrete to a continental plate margin. These multiple collisions produce a complex network of faults (breaks in the Earth's otherwise largely impermeable crust) in the resulting mountain belts, that can be prone to later slip (reactivation). The faults can be efficient pathways for the transfer of rock melt (magma), fluids and heat, which facilitate the flux and concentration of metals. Many ore-deposit settings (e.g. deformation zones, intrusions, basins) occur within or proximal to accretionary orogen fault systems, and host metals, many of which are considered essential for Canada's future society (e.g., Sn, W, Mo, In, Au, Bi, Co, U). The long-term objective of my research program is to document the fault, fluid and thermal records of orogenic upper crust and relate them to geodynamic processes and ore-deposit formation. My recent work has focused on coeval geological, structural and ore-system records in Canada's flanking accretionary orogens, the east coast Canadian Appalachians and the west coast Canadian Cordillera. These studies suggest that ore-relevant processes may have been triggered by perturbations of the Earth's lithospheric mantle (the layer of the Earth that underlies the crust) beneath accreted terranes. My short term objectives (O1-3) are focused around testing that hypothesis in these two orogens. Over the next five years, I will (O1) reconstruct the temperature-time and structural evolution of the upper crust during post-accretionary reactivation of orogenic fault zones using field mapping, analysis of rock microstructures, and petrochronology and thermochronology rock dating methods. I will (O2) determine the fault-fluid-critical metal mineralization relationships during these periods using novel methods including U-Pb dating of slickenfibres and veins, K-Ar dating of fault gouge clay and stable and clumped isotopes. Finally, I will (O3) explore how lithospheric perturbations such as subducted slab break-off and delamination may influence the temperature-time evolution of the upper crust in a post-accretionary orogenic setting via numerical modeling. This work will result in a refined framework for long-term fault behaviour in accretionary orogens, particularly in the contexts of orogen lithosphere evolution and ore-deposit formation. Results will contribute to Canada's ability to search for its critical mineral resources. HQP involved in conducting this research will collaborate with world-class laboratories, industry, and government, and will develop transferable skills in analytical research, data management, common structural geology and ore deposits field and laboratory research methods, and science communication.

随着大陆和海洋碎片（地体）携带俯冲海洋板块增生到大陆板块边缘，增生造山带（山脉）经过数千万年至数亿年形成。这些多次碰撞在由此产生的山带中产生了复杂的断层网络（地球原本基本上不渗透的地壳破裂），这些断层很容易在以后发生滑动（重新激活）。断层是岩石熔体（岩浆）、流体和热量传递的有效通道，有利于金属的流动和集中。许多矿床环境（例如变形带、侵入体、盆地）发生在增生造山带断层系统及其附近，其中许多金属被认为对加拿大的未来社会至关重要（例如锡、钨、钼、铟、金） ，Bi，Co，U）。我的研究计划的长期目标是记录造山带上地壳的断层、流体和热记录，并将它们与地球动力学过程和矿床形成联系起来。我最近的工作重点是加拿大侧翼增生造山带、加拿大东海岸阿巴拉契亚山脉和西海岸加拿大科迪勒拉山脉的同期地质、结构和矿石系统记录。这些研究表明，与矿石相关的过程可能是由增生地体下方的地球岩石圈地幔（地壳下方的地球层）的扰动引发的。我的短期目标 (O1-3) 重点是在这两个造山带测试该假设。在接下来的五年中，我将（O1）利用现场测绘、岩石微观结构分析以及岩石年代学和热年代学岩石测年方法，重建造山断裂带后增生再活动期间上地壳的温度-时间和结构演化。我将 (O2) 使用新颖的方法确定这些时期的断层-流体-临界金属矿化关系，包括对光滑纤维和矿脉进行 U-Pb 测年、对断层泥粘土进行 K-Ar 测年以及稳定和团簇同位素。最后，我将（O3）通过数值模拟探讨俯冲板片断裂和分层等岩石圈扰动如何影响增生后造山环境中上地壳的温度-时间演化。这项工作将为增生造山带的长期断层行为提供一个完善的框架，特别是在造山带岩石圈演化和矿床形成的背景下。 结果将有助于加拿大寻找其关键矿产资源的能力。参与开展这项研究的总部将与世界一流的实验室、行业和政府合作，并将开发分析研究、数据管理、共同构造地质学和矿床领域和实验室研究方法以及科学传播方面的可转移技能。