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: 2217811
• 负责人: Cailey Condit
• 金额: $ 25.32万
• 依托单位: University of Washington
• 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 2025-11-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2217811&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.

俯冲带是地球上最具破坏性的地质危害在内的所在地，包括大巨星地球爆发和海啸。大地成核和缓慢计算的俯冲带的一部分被称为地震区的基础，也是发生强烈的化学变化和流体流动的区域。了解与这些岩石相关的时间和过程，这些岩石在俯冲带的这一部分中与流体相互作用，对于进一步限制这些地震和全球元素循环至关重要。但是，我们目前缺乏强大的工具。该项目旨在开发磷灰石石化学，即从普通矿物磷灰石的单个晶粒的年代，化学和纹理数据的整合，以直接在俯冲地震源性区底部发生的化学和机械过程。拟议的研究将为研究俯冲区以及变形和流体岩石相互作用的研究人员提供新的工具。这项工作的更广泛的影响围绕提供教育和研究机会，通过开发虚拟现场视频游戏模块，将现场观察和实验室观测和岩石学，微观结构和按时间顺序从这项研究产生的结果来提高地球科学的包容性和可访问性。这些视频游戏将使学生有机会获得现场技能，并将露头链接到微观观察结果，同时包含在所有学生中（即没有与成本或能力相关的障碍）。这项研究支持两名早期职业女性科学家，一名女性博士后研究人员，并将支持UNLV的本科生和研究生。俯冲地震生成区的底座发生在30-50 kms的深度和温度〜200-500°C的深度，是大型的大型巨型大地地震核和神秘的断层区的行为，例如情景树和滑移。这也是一个强烈的化学转化领域，包括脱脂化，流体流和变质。化学，机械和流体过程沿板界面发生可能起着重要的作用，这会影响相对凉爽的绿色绿色和蓝色变质设施（250°C -500°C）内俯冲地震生成区的变形样式。目前，在这些相对冷的变质岩石中，我们缺乏良好的原位时间表，这使得将直接定时限制放在这些化学和机械过程中的挑战。磷灰石是许多俯冲带岩性中一种常见的辅助矿物，在变形过程中动态重结晶，在流体流动过程中溶解和重新沉淀，化学跟踪变态和转移反应，从而使其成为恢复链接的微观结构性 - 超大型型 - 更大程度 - 更大度的时间数据的潜在变革性工具。该项目检验了以下假设：磷灰石U-PB石化学可以直接约会变形，变质和（或（或）从俯冲地震基地底部挖出的岩石中的流体流动。 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岩性。他们的结果将系统地限制磷灰石在不同的P-T和流体条件上的物理和化学行为，并促进磷灰石EPMA映射的方法开发，从而产生用于恢复链接的微结构T-T数据的变换工具。最终，这将提供流变学，年代学和地球化学的约束，从诱发的俯冲相关岩石中产生，这些岩石可以与远程观察（例如，地震，地震学，地质数据）相结合，以更好地理解俯冲地震的复杂性，蔓延，蠕动的变形事件，缓慢的滑移事件，慢速事件，慢速变化，在Metamorphism，Metamorphism和Metamorphism和Metamorphism和Metamorphism和Metamempsism和Flof Flowicmiss和Fluff Flowicmism和Fluff Flowicmiss和Fluff Flofcommiss和Flof Flofsism和Fluff Flofcism和Flof Flowicmiss中。该奖项反映了NSF的法定使命，并通过使用基金会的知识分子优点和更广泛的审查标准评估来诚实地获得支持。