EAGER: Collaborative Research: Mantle fluid contribution to springs along the Denali Fault System: Constraints on the crustal scale nature of the main strand and splays

EAGER：合作研究：地幔流体对德纳里断层系统沿线泉水的贡献：对主链和斜张地壳尺度性质的限制

• 批准号: 2016336
• 负责人: Sean Regan
• 金额: $ 5.76万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-01 至 2022-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2016336&HistoricalAwards=false
• 关键词: EAGER; Collaborative; Research; Mantle; fluid

The Denali Fault in Alaska is a 2000-km-long, active, predominately horizontal motion (strike-slip) fault zone associated with the boundary between the North American and the Pacific tectonic plates. Fault zones are breaks in the Earth’s crust that can act as conduits for transport of water from great depths (20 miles). Major questions exist about how deeply this fault penetrates into the crust, how the multiple strands of the fault are connected at depth, and how the changes in the style of faulting along its trace impact the circulation of deep groundwater. To inform these unknowns, this study will examine the isotope geochemistry of springs that discharge along the Denali fault zone. Results will improve the understanding of the Denali Fault, particularly with respect to the depth and interconnectedness of fault strands, with important implications for earthquake hazards and the distribution of geothermal and mineral resources. This study fosters a new interdisciplinary collaboration between investigators in Alaska and Utah, and advances education and training for undergraduate students, including those from underrepresented groups.This one-year project will examine the helium isotope signature of springs discharging along the Denali Fault system and along splay thrust faults. The fault system transitions east-to-west from a transform fault to a continental strike-slip fault, and provides a system to test hypotheses on the nature of continental strike-slip faults and splay thrust faults as potential conduits for mantle-derived fluids. Helium isotope (3He/4He), carbon, oxygen, and hydrogen stable isotope, and water chemistry data from springs will constrain the contribution of mantle-derived fluids to test competing geophysics models on variations in the crustal scale of the Denali Fault system, the depth splay faults connect with the master strand of the Denali Fault, and possible influences of the underlying subducting slab geometry on fluid isotopic composition. For this exploratory study, ten springs were selected along the trace of the Denali Fault system in Alaska, including six CO2-rich springs that deposit travertine to maximize capturing signals from deep flow paths. In addition to advancing understanding of the structural and geochemical record of fluid-fault interaction, this study provides a framework for future helium isotopic analysis of additional springs along the Denali Fault system, other regional structures, and the tectonic-magmatic regime responsible for geothermal resources across Alaska.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

阿拉斯加的迪纳利断层是一条长 2000 公里的活跃的、以水平运动（走滑）为主的断层带，与北美和太平洋构造板块之间的边界相关。断层带是地壳中可以活动的断裂带。作为从深处（20英里）输送水的管道，存在的主要问题是该断层渗透到地壳的深度、断层的多条线在深度上如何连接以及如何变化。为了了解这些未知因素，本研究将研究沿德纳利断层带流出的泉水的同位素地球化学结果，这将增进对德纳利断层的了解，特别是在这方面。这项研究促进了阿拉斯加和犹他州研究人员之间新的跨学科合作，并促进了本科生的教育和培训。这个为期一年的项目将研究沿着迪纳利断层系统和沿着张开逆冲断层排放的泉水的氦同位素特征。该断层系统从东向西从转换断层过渡到大陆走向。 -滑动断层，并提供了一个系统来检验大陆走滑断层和张开逆冲断层作为地幔衍生流体的潜在管道的性质的假设。同位素（3He/4He）、碳、氧和氢稳定同位素以及来自泉水的水化学数据将限制地幔衍生流体的贡献，以测试关于德纳里断层系统地壳规模、深度的变化的竞争地球物理模型张开断层与德纳里断层的主链相连，以及下方俯冲板块几何形状对流体同位素组成的可能影响。在这项探索性研究中，沿线选择了十个泉水。阿拉斯加迪纳利断层系统的痕迹，包括六个富含二氧化碳的泉水，这些泉水沉积了石灰华，以最大限度地捕获来自深层流动路径的信号。除了加深对流体与断层相互作用的结构和地球化学记录的理解之外，这项研究还提供了一个框架。用于未来对德纳里断层系统沿线的其他泉水、其他区域结构以及负责整个阿拉斯加地热资源的构造岩浆体系进行氦同位素分析。该奖项反映了 NSF 的法定使命，并被认为是值得的通过使用基金会的智力优势和更广泛的影响审查标准进行评估来获得支持。