Testing contrasting models for the distribution of hydrothermal circulation in subducting crust

测试俯冲地壳中热液循环分布的对比模型

• 批准号: 1551587
• 负责人: Glenn Spinelli
• 金额: $ 20.34万
• 依托单位: New Mexico Institute of Mining and Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2020-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1551587&HistoricalAwards=false
• 关键词: Testing; contrasting; models; distribution; hydrothermal

Subduction zones are where one of Earth's tectonic plates moves under another resulting in many of the world's largest earthquakes and damaging tsunamis. One example is the 2011 earthquake and tsunami in northern Japan that killed more than 20,000 people and crippled the Fukushima Daiichi nuclear complex. These earthquakes arise from friction on the subduction zone fault that separates the two tectonic plates. The temperature of the subduction fault zone affects this friction and can control the size and distribution of earthquakes. In addition, subduction zone temperatures affect a wide range of other physical and chemical processes, including the generation of magma that supplies nearby volcanoes. To understand these processes, it is important to accurately estimate subduction zone temperatures. Recent discoveries show that seawater circulating within the subducting tectonic plates is an important control on subduction zone temperatures. This project will examine how fractures that open in the upper part of a tectonic plate as it bends down into a subduction zone affect seawater circulation in the system and how that affects subduction zone temperatures. The project will develop numerical thermal models for seven subduction zones. Application of the results of this research has direct societal benefit, by informing earthquake hazard estimates. In addition, the project will enhance education at New Mexico Tech, a STEM-focused Hispanic-serving institution. A graduate student will be trained in geophysics and hydrogeology. Results of the project will be incorporated into "using data in the classroom" efforts, improving hands-on experience in undergraduate courses.Accurate subduction zone thermal models are necessary to understand frictional behavior, metamorphic reaction progress, release of volatiles from the subducting slab, mantle wedge hydration, subduction dynamics, and melt generation. Fluid circulation in an oceanic crustal aquifer is an important control on subduction zone temperatures. However, there are contrasting hypotheses for how much of the oceanic crust can host vigorous hydrothermal circulation. Both thickening of the oceanic crustal aquifer via plate bending normal faults and fluid circulation between subducted crust and the crust seaward of the trench may contribute to the advective redistribution of heat that affects subduction zone temperatures. This project will test the hypothesis that the thermal effects of aquifer thickening prior to subduction are greater for slabs with a greater degree of curvature. This project will exploit the fact that aquifer thickening from the outer rise to the trench and continued fluid circulation in subducting crust are expected to produce distinct surface heat flux anomalies (a broad low amplitude anomaly for aquifer thickening; a narrow high amplitude anomaly for fluid circulation in subducting crust) in order to constrain the thermal effects of each process. This will advance our understanding of the fluid circulation process that is an important control on subduction zone temperatures, improving subduction zone thermal models for the seven margins examined in this project and others.

俯冲带是地球的一个构造板块在另一个板块之下移动的地方，导致了许多世界上最大的地震和破坏性的海啸。一个例子是2011年日本北部发生的地震和海啸，造成2万多人死亡，福岛第一核电站瘫痪。这些地震是由分隔两个构造板块的俯冲带断层上的摩擦引起的。俯冲断裂带的温度影响这种摩擦，并可以控制地震的大小和分布。此外，俯冲带的温度还会影响广泛的其他物理和化学过程，包括为附近火山提供补给的岩浆的产生。为了理解这些过程，准确估计俯冲带温度是很重要的。最近的发现表明，在俯冲构造板块内循环的海水是俯冲带温度的重要控制因素。该项目将研究构造板块上部向下弯曲进入俯冲带时打开的裂缝如何影响系统中的海水循环，以及如何影响俯冲带温度。该项目将开发七个俯冲带的数值热模型。应用这项研究的结果具有直接的社会效益，因为它为地震风险估计提供了信息。此外，该项目将加强新墨西哥理工学院的教育，这是一家专注于STEM的拉美裔服务机构。一名研究生将接受地球物理和水文地质学方面的培训。该项目的成果将被纳入“在课堂上使用数据”的工作中，改善本科生的实践体验。准确的俯冲带热模型对于理解摩擦行为、变质反应过程、从俯冲板块释放挥发分、地幔楔形水化、俯冲动力学和熔体生成是必要的。大洋地壳含水层中的流体循环是俯冲带温度的重要控制因素。然而，关于洋壳中有多少可以承载旺盛的热液循环，存在着截然不同的假设。大洋地壳含水层通过板块弯曲正断层的增厚和俯冲地壳与海沟地壳之间的流体循环都可能有助于影响俯冲带温度的平流热重新分配。该项目将检验这样一种假设，即在俯冲之前，含水层加厚的热效应对于曲率程度较大的板块来说更大。该项目将利用以下事实：从外部隆起到海沟的含水层增厚和俯冲地壳中持续的流体循环预计将产生明显的地表热通量异常(含水层增厚的宽幅低幅度异常；俯冲地壳流体循环的狭窄高幅度异常)，以限制每个过程的热效应。这将促进我们对流体循环过程的理解，流体循环过程是俯冲带温度的重要控制因素，改进了本项目和其他项目中研究的七个边缘的俯冲带热模型。

项目成果

Diagenetic, metamorphic, and hydrogeologic consequences of hydrothermal circulation in subducting crust

俯冲地壳热液循环的成岩、变质和水文地质后果

• DOI: 10.1130/ges01653.1
• 发表时间: 2018
• 期刊: Geosphere
• 影响因子: 2.5
• 作者: Spinelli, Glenn;Wada, Ikuko;Wang, Kelin;He, Jiangheng;Harris, Robert;Underwood, Michael
• 通讯作者: Underwood, Michael