Collaborative Research: Apatite petrochronology and microtextural analyses: a new tool to directly date subduction processes at the base of the seismogenic zone

合作研究：磷灰石岩石年代学和微观结构分析：直接测定地震带底部俯冲过程的新工具

• 批准号: 2217810
• 负责人: Margaret Odlum
• 金额: $ 37.02万
• 依托单位: University of Nevada Las Vegas
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2023-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2217810&HistoricalAwards=false
• 关键词: Collaborative; Research; Apatite; petrochronology; microtextural

Subduction zones are the locus for the most destructive geological hazards on earth including megathrust earthquakes, volcanic eruptions, and tsunami. The portion of the subduction zone where large earthquakes nucleate and slow earthquakes occur, known as the base of the seismogenic zone, is also an area where intense chemical change and fluid flow occurs. Understanding the timing and processes associated with these rocks deformating and interacting with fluids in this part of the subduction zone is critical for further constraining these earthquakes and global element cycling. However, we currently lack robust tools to do so. This project aims to develop apatite petrochronology, the integration of chronologic, chemical, and textural data from single grains of the common mineral apatite, to directly date chemical and mechanical processes that occurred at the base of the subduction seismogenic zone. The proposed research will provide new tools for researchers studying subduction zones as well as deformation and fluid-rock interactions more broadly. The broader impacts of this work center around providing education and research opportunities that increase inclusivity and accessibility in geoscience through the development of virtual field video game modules that integrate field and lab observations and with petrologic, microstructural, and chronological results from this research. These video games will give students opportunities to gain field skills and link outcrop to microscale observations, while being inclusive and accessible to all students (i.e., no barriers associated with cost or able-bodiedness). This research supports two early career female scientists, a female postdoctoral researcher, and will support an undergraduate and graduate student at UNLV. The base of the subduction seismogenic zone, which occurs at depths of 30-50 kms and temperatures ~200-500°C, is where both large megathrust earthquakes nucleate and enigmatic fault zone behaviors such as episodic tremor and slip occur. This is also an area of intense chemical transformation including devolatilization, fluid flow, and metamorphism. Chemical, mechanical, and fluid processes occurring along the plate interface likely play an important role in influencing the deformation style of the base of the subduction seismogenic zone within the relatively cool greenschist and blueschist metamorphic facies (250°C - 500°C). We currently lack well constrained in situ chronometers in these relatively cold metamorphic rocks, making it challenging to place direct timing constraints on these chemical and mechanical processes in exhumed subduction complexes. Apatite, a common accessory mineral in many subduction zone lithologies, dynamically recrystallizes during deformation, dissolves and reprecipitates during fluid flow, and chemically tracks metamorphic and metasomatic reactions making it a potentially transformative tool for recovering linked microstructure-metamorphism-Temperature-time data. This project tests the hypothesis that apatite U-Pb petrochronology can directly date deformation, metamorphism, and(or) fluid flow in rocks exhumed from the base of the subduction seismogenic zone. Through coupled microstructural (petrographic, EBSD), geochemical (EPMA, LA-ICP-MS), and geochronological (LA-ICP-MS) techniques the researchers will directly date these processes in four exhumed subduction complexes (C. Alps, Catalina Schist, & Crete/Andros, Greece) representing different stages of the subduction evolution across a range of P-T-fluid conditions and lithologies. Their results will systematically constrain the physical and chemical behavior of apatite across different P-T and fluid conditions and facilitate method development of EPMA mapping of apatite, yielding transformative tools for recovering linked microstructure-T-t data. Ultimately, this will provide rheologic, geochronologic, and geochemical constraints on from exhumed subduction related rocks that can be integrated with remote observations (e.g., seismology, geodetic data) to better understand complexities of subduction earthquakes, creeping deformation, slow slip events, and chemical transformations during metamorphism, metasomatism, and fluid flow.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.

俯冲区是地球上最具破坏性的地质危害，包括大地震，tsun ami。地震和全球元素骑自行车。俯冲地震生成区。将领域和实验室观察和岩石学，微观结构和年代学结果整合的游戏模块将为学生提供适当的技能技能，并将露头链接到微观的观察结果（即，没有与成本或能力相关的障碍） 。例如发作或滑移，这也是静脉化学转化俯冲带有凉爽的绿色绿色和蓝色变质相（250°C -500°C）。在流体流动期间溶解和重新沉淀，化学跟踪变质和变质的ITA潜在的势力型工具，用于繁殖 - 超态 - 型 - 温度 - 温度时间数据。 ）从细分地震生成带（EPMA，LA-ICP-MS）和地质（LA-ICP-MS）技术的岩石中的岩石流中的岩石流量将直接约会。 catalina学校的阶段，跨P-T-Fluid凝结和岩性的演变的阶段将有系统地限制APATITE的物理行为和化学行为。为了最终，这将提供流变学，而地球化学来自散发相关的岩石，这些岩石可以与远程观测（例如，地震学，地理数据）整合在一起，并在变质，交代和流体流动期间的化学转化。该奖项反映了Ory的使命，并被认为是通过使用Toundation的知识分子优点和更广泛影响的审查标准来评估值得支持的。