Investigation of fluids and hydrated mantle in subduction zones, with a focus on Cascadia

研究俯冲带的流体和水合地幔，重点关注卡斯卡迪亚

• 批准号: RGPIN-2020-07066
• 负责人: Peacock, Simon
• 金额: $ 2.55万
• 依托单位: University of British Columbia
• 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=741267
• 关键词: Investigation; fluids; hydrated; mantle; subduction

Earth's most damaging earthquakes and volcanic eruptions occur along subduction-zone plate boundaries where oceanic lithosphere descends into the mantle. For example, the magnitude (M) 9.0 subduction-zone earthquake that struck Tohoku, Japan on March 11, 2011 resulted in the loss of >19,000 lives and estimated damages of US$235B. The Cascadia subduction zone extends for >1,000 km along the west coast of North America from Vancouver Island to northern California. Rupture of the Cascadia plate boundary has resulted in great M9 earthquakes every ~500 years, with the last one occurring on January 26, 1700 AD. Damaging Cascadia earthquakes also occur within the subducting Juan de Fuca and overriding North American plates.     Subduction-zone earthquakes are linked to the generation, transport, and resorption of water-rich fluids. Understanding the mechanical behaviour of the plate boundary, and therefore the seismic potential, requires understanding the distribution of hydrous minerals and fluids along the boundary. Recent work has demonstrated that the distribution of earthquakes in the overriding plate is linked to the permeability of the plate boundary and the extent to which fluids generated at depth escape into the overlying crust. At deeper levels, fluids released from the subducting plate hydrate the overlying mantle forming serpentine, talc, and other weak minerals.     My five-year program of research supports my long-term objective to better understand subduction zones and leverages my previous modelling efforts. My short-term objectives focus on subduction-zone fluids that infiltrate the mantle wedge. Specifically, I propose to (1) construct mineralogical maps of the mantle wedge as a function of bulk composition and H2O content, (2) conduct field-based petrologic studies to constrain the spatial scale(s) of H2O equilibrium in hydrated mantle rocks, and (3) develop an integrated model of fluid flow in the Cascadia subduction zone as illuminated by seismicity. The mineralogical maps will be constructed by combining numerical heat transfer and thermodynamic models, integrating the results with seismological observations. Field work will focus on ultramafic rocks exposed in British Columbia and Washington state.     I propose to train a diverse HQP group consisting of three graduate students (1 PhD and 2 MSc) and one undergraduate student using equitable and inclusive recruitment and mentoring practices. Research training in thermal-petrologic modelling techniques and metamorphic petrology will provide a strong foundation for these students to pursue academic and technical careers.     The results of the proposed program of research will further our understanding of subduction zone fluids and earthquakes, potentially opening up new avenues to improve long-term forecasting of seismic hazards. Research results will be presented at international geoscience meetings and workshops, and published in high-quality peer-reviewed journals.

地球最具破坏性的地震和火山喷发发生在俯冲区板板边界，海洋岩石圈降落到地幔中。例如，2011年3月11日袭击日本Tohoku的巨大（M）9.0俯冲区地震导致损失> 19,000次丧生，估计损失了235B美元。卡斯卡迪亚俯冲带沿北美西海岸从温哥华岛到北加州延伸> 1,000公里。卡斯卡迪亚板块边界的破裂导致每500年发生一次大M9地震，最后一个发生在公元1700年1月26日。在俯冲的胡安·德福卡（Juan de Fuca）和压倒北美板块内，也发生了破坏性的卡斯卡迪亚地震。俯冲区域地震与富含水的流体的产生，运输和分辨率有关。了解板界的机械行为，因此需要地震势，需要了解沿边界的含水矿物和流体的分布。最近的工作表明，覆盖板中的地震的分布与板界的渗透性以及深度在深度逃脱到上覆盖的地壳时产生的渗透性有关。在更深层次的水平下，从俯冲板中释放出的流体水合释放出上覆的地幔形成蛇形，滑石粉和其他弱矿物质。我的五年研究计划支持我的长期目标，以更好地了解俯冲区并利用我以前的建模工作。我的短期目标集中于渗透地幔楔的俯冲区域流体。 Specifically, I propose to (1) construct mineralogical maps of the mantle wedge as a function of bulk composition and H2O content, (2) conduct field-based petrologic studies to constrain the spatial scale(s) of H2O Equilibrium in hydrated mantle rocks, and (3) develop an integrated model of fluid flow in the Cascadia subduction zone as illuminated by seismicity.矿物学图将通过结合数值传热和热力学模型来构建，从而将结果与地震学观测结合在一起。现场工作将集中在不列颠哥伦比亚省和华盛顿州暴露的超镁铁质岩石上。我建议培训由三名研究生（1位博士学位和2个MSC）组成的潜水HQP小组，并使用公平和包容的招聘和心理实践来培训一名本科生。热准学建模技术和变质岩石学的研究培训将为这些学生从事学术和技术职业提供坚实的基础。拟议的研究计划的结果将进一步了解俯冲带流体和地震，这可能开辟了新的途径，以改善对地震危害的长期预测。研究结果将在国际地球科学会议和研讨会上介绍，并在高质量的同行评审期刊上发表。