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

阿拉斯加的迪纳利断层是一个2000公里长的活跃的、主要水平运动（走滑）的断层带，与北美和太平洋构造板块之间的边界有关。断层带是地壳中的断裂，可以作为从很深（20英里）运输水的管道。主要的问题是，这条断层深入地壳有多深，断层的多股在深度上是如何连接的，以及断层沿着走向的样式变化如何影响深层地下水的循环。为了告知这些未知数，这项研究将检查沿着德纳里断层带排放的泉水的同位素地球化学。研究结果将提高对德纳里断层的认识，特别是断层带的深度和相互连接性，对地震灾害以及地热和矿产资源的分布具有重要意义。这项研究促进了阿拉斯加州和犹他州的研究人员之间新的跨学科合作，并促进了对本科生的教育和培训，包括那些来自代表性不足的群体。这个为期一年的项目将研究沿着德纳里断层系统和沿着展状逆冲断层排放的泉水的氦同位素特征。断层系统从东向西从转换断层过渡到大陆走滑断层，并提供了一个系统来测试假设的性质大陆走滑断层和展布逆冲断层作为潜在的管道幔源流体。氦同位素（3 He/4 He），碳，氧，氢稳定同位素，和水的化学数据，从春天将限制的贡献，幔源流体测试竞争的地球物理学模型的变化，在地壳规模的德纳里断层系统，深度展布断层连接与主链的德纳里断层，以及潜在的俯冲板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，沿着阿拉斯加德纳里断层系统的痕迹选择了10个泉水，其中包括6个富含二氧化碳的泉水，这些泉水存款可最大限度地捕获来自深部流动路径的信号。除了推进对流体-断层相互作用的结构和地球化学记录的理解外，这项研究还为今后沿着德纳里断层系统、其他区域构造、和构造-该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准。

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.