Collaborative Research: RUI: Reframing Notions of Wet vs. Dry Subduction: The Search for a Deep Fluid Signature in Subducted Continental Crust Using Coupled O, B, and Fe Isotopes

合作研究：RUI：重新定义湿俯冲与干俯冲的概念：使用 O、B 和 Fe 耦合同位素在俯冲大陆壳中寻找深层流体特征

• 批准号: 1822526
• 负责人: Carrie Menold
• 金额: $ 7.51万
• 依托单位: Albion College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-15 至 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1822526&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Reframing; Notions

Subduction zones represent not only the main mechanism of mass transfer between the Earth's surface and interior, but also the setting for a majority of large earthquakes and a source of significant volcanic activity, both of which have dramatic and direct effects on human civilization. The presence, scale, and nature of fluids in deep portions of subduction zones are undoubtedly important factors in the generation of both earthquakes and magma, and therefore must be identified and characterized. This study will contribute to our current understanding of deep fluids in subduction zones, and potentially establish a new method for studying them. It would also, as the title suggests, reframe notions of wet versus dry subduction, which may open the door to other ideas and methods for studying subduction zone processes. This project will provide training and research opportunities for a diverse group of graduate and undergraduate students. Outreach activities at local GK-12 schools will expose potential future scientists to cutting edge Earth Science.Small volumes of continental crust surrounded by oceanic crust may be subducted to ultrahigh-pressure (UHP) depths and exhumed in the early stages of orogeny. These small, subducted blocks of continental crust can preserve evidence of large-scale, deep subduction fluid metasomatism. This team hypothesizes that the Tso Morari terrane, a young UHP locality in the NW Himalaya, represents a small, early-subducted continental mass that likely experienced metasomatism at UHP in the subduction zone. Recent advances have led to novel isotopic and geochemical proxies to fingerprint the origin of subduction-derived fluids and melts both in exhumed subduction materials and arc magmas. In particular, boron is expected to be enriched in devolatilized fluids and depleted in the corresponding host rocks with boron isotopic values providing a sensitive indication of the extent of devolatilization. Additionally, iron isotope systematics are emerging as a potentially powerful tracer of the nature of slab derived fluids. This project will combine these novel proxies with the more established and traditional tracers of subduction fluids, including oxygen isotopes, thermodynamic and fluid modeling, bulk-rock geochemistry, ferrous/ferric iron ratios on a suite of UHP rocks and associated ophiolite/melange from the Tso Morari.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.

俯冲带不仅代表了地球表面和内部之间物质传递的主要机制，而且也是大多数大地震的发生地和重要火山活动的来源，这两者都对人类文明产生巨大和直接的影响。俯冲带深处流体的存在、规模和性质无疑是地震和岩浆产生的重要因素，因此必须对其进行识别和表征。这项研究将有助于我们目前对俯冲带深层流体的理解，并有可能建立一种研究它们的新方法。正如标题所示，它还将重新构建湿俯冲与干俯冲的概念，这可能为研究俯冲带过程的其他想法和方法打开大门。该项目将为不同群体的研究生和本科生提供培训和研究机会。当地 GK-12 学校的外展活动将使未来潜在的科学家接触最前沿的地球科学。被洋壳包围的少量大陆地壳可能会俯冲到超高压 (UHP) 深度，并在造山运动的早期阶段被挖掘出来。这些小型俯冲大陆地壳块可以保存大规模深俯冲流体交代作用的证据。该团队假设，Tso Morari 地体是喜马拉雅山西北部的一个年轻的超高压地点，代表了一个小型的早期俯冲大陆块，该大陆块可能在俯冲带的超高压处经历了交代作用。最近的进展催生了新的同位素和地球化学代理，可以对挖出的俯冲物质和弧岩浆中俯冲衍生流体和熔体的起源进行指纹识别。特别是，硼预计会在脱挥发分流体中富集，并在相应的主岩中贫化，硼同位素值可提供脱挥发分程度的敏感指示。此外，铁同位素系统学正在成为板片衍生流体性质的潜在强大示踪剂。该项目将把这些新颖的代理与更成熟和传统的俯冲流体示踪剂相结合，包括氧同位素、热力学和流体建模、块体岩石地球化学、一套超高压岩石的二价铁/三价铁比率以及来自措莫拉里的相关蛇绿岩/混杂岩。该奖项反映了 NSF 的法定使命，并通过评估被认为值得支持 利用基金会的智力优势和更广泛的影响审查标准。