Collaborative Research: Investigating the Detachment Fault Cycle at the Mid-Cayman Spreading Center

合作研究：调查开曼中部扩张中心的脱离断层旋回

• 批准号: 2104437
• 负责人: Ross Parnell-Turner
• 金额: $ 44.85万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-01-01 至 2025-12-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2104437&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Detachment; Fault

Continuous paving of new seafloor at the center of the oceans is one the fundamental processes that shape Earth’s surface. Where plates spread apart relatively quickly, new crust is formed as molten rock rises to the surface, and cools to form solid crust. Where the plates move apart more slowly less molten rock fills the gap, and instead, plate separation is taken up by motion on long-lived faults called detachments. Creation of new oceanic seafloor by slip on these kilometer-scale faults is poorly understood, and is associated with hydrothermal vent systems that provide metal-rich fluids, which create ore deposits and support thriving deep-sea ecosystems. One of the best ways to understand the behavior of these faults is to study the earthquakes that they generate. This project will use earthquake data recorded by a network of seafloor seismometers, deployed on a detachment fault system where two plates are spreading apart in the Caribbean Sea, at the Mid-Cayman Spreading Center. The results will help us understand the final stages of the ‘life cycle’ of an oceanic detachment fault, by monitoring the faulting, magmatism, and hydrothermal fluid flow in the subsurface. This project supports the training of a graduate student at the University of California San Diego, and a postdoctoral investigator at Woods Hole Oceanographic Institution. It also supports the training of undergraduate students, through participation in a sea-going research expedition and summer programs.The overarching goal of this project is to understand the processes that govern the late stages of the detachment faulting life cycle, and the processes by which the fault system is abandoned, in particular. Oceanic detachments undergo a life cycle of slip and abandonment that lasts millions of years, and commonly expose upper mantle rocks on the seafloor in kilometer-scale domes called oceanic core complexes. Although they form in magma-poor settings, detachments often host high-temperature hydrothermal systems, and interactions between hydrothermal vents and ultramafic rocks generate fluids with distinct compositions. Detachment faults are associated with a delicate interplay between tectonic, magmatic, and hydrothermal processes, but how such interactions evolve over the ~2 Myr life cycle are controversial. This project will use a local microearthquake survey of the Mt. Dent massif on the Mid-Cayman Spreading Center, to constrain the tectono-magmatic processes associated with the late stage of the life cycle. A network of ocean bottom seismographs will be deployed for 6–12 months to detect microearthquake arrivals, which will be used to generate hypocenter and focal mechanism catalogs, and also to test new full-waveform methods for detecting and locating hypocenters.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.

海洋地壳中心不断形成新的海底是塑造地球表面的基本过程之一，板块相对较快地分开，当熔融岩石上升到地表并冷却形成固体地壳时，新的板块会进一步分开。慢慢地，越来越少的熔岩填充了间隙，相反，板块分离被称为分离的长期断层上的运动所取代，通过这些公里级断层上的滑动来形成新的海底是很困难的。理解这些断层，并与提供富含金属的流体的热液喷口系统相关，这些流体产生矿床并支持繁荣的深海生态系统，了解这些断层行为的最佳方法之一是研究它们产生的地震。该项目将使用海底地震仪网络记录的地震数据，该网络部署在加勒比海中开曼传播中心的两个板块分开的脱离断层系统上。结果将帮助我们了解地震的最后阶段。通过监测地下的断层、岩浆作用和热液流动，研究海洋脱离断层的“生命周期”。该项目支持对加州大学圣地亚哥分校的一名研究生和伍兹霍尔海洋学的一名博士后研究员进行培训。它还通过参加海上研究考察和暑期项目来支持本科生的培训。该项目的总体目标是了解控制分离断层生命周期后期的过程以及过程。由此特别是，断层系统被遗弃，经历了持续数百万年的滑动和遗弃的生命周期，并且通常将上地幔岩石暴露在海底，称为洋核复合体，尽管它们是在岩浆中形成的。在恶劣的环境下，分离断层通常存在高温热液系统，热液喷口和超镁铁质岩石之间的相互作用产生具有不同成分的流体，分离断层与之间的微妙相互作用有关。构造、岩浆和热液过程，但这种相互作用如何在约 2 Myr 的生命周期中演变是有争议的。该项目将使用开曼中部传播中心的登特山地块的局部微地震调查来限制构造。与生命周期后期相关的岩浆过程将部署为期 6 至 12 个月的海底地震仪网络，以检测微地震的到来。生成震源和震源机制目录，并测试用于检测和定位震源的新全波形方法。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。