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移动到另一个构造板块下方的地方，导致世界上许多最大的地震和破坏性海啸。一个例子是 2011 年日本北部的地震和海啸，造成 20,000 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。 俯冲断层带的温度影响这种摩擦力，可以控制地震的规模和分布。此外，俯冲带温度影响广泛的其他物理和化学过程，包括供应附近火山的岩浆的产生。为了了解这些过程，准确估计俯冲带温度非常重要。最近的发现表明，俯冲构造板块内循环的海水是对俯冲带温度的重要控制。该项目将研究当构造板块向下弯曲到俯冲带时在其上部张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。该项目将为七个俯冲带开发数值热模型。通过为地震灾害估计提供信息，本研究结果的应用具有直接的社会效益。此外，该项目还将加强新墨西哥理工学院的教育，这是一家专注于 STEM 的西班牙裔服务机构。研究生将接受地球物理学和水文地质学方面的培训。该项目的成果将纳入“课堂数据使用”工作，提高本科生课程的实践经验。准确的俯冲带热模型对于了解摩擦行为、变质反应进程、俯冲板片挥发物的释放、地幔楔水合作用、俯冲动力学和熔体生成。洋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，对于有多少洋壳可以容纳剧烈的热液循环，存在着相反的假设。板块弯曲正断层导致的洋壳含水层增厚以及俯冲地壳和海沟向海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再分布。该项目将测试以下假设：俯冲前含水层增厚的热效应对于曲率较大的板片而言更大。该项目将利用以下事实：从外隆起到海沟的含水层增厚以及俯冲地壳中持续的流体循环预计会产生明显的表面热通量异常（含水层增厚的广泛低振幅异常；流体循环的狭窄高振幅异常）在俯冲地壳中），以限制每个过程的热效应。这将增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，改进本项目和其他项目中检查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: 2018-10
• 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