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

俯冲带不仅是地球表面和内部之间物质转移的主要机制，而且也是大多数大地震的背景和重大火山活动的来源，这两者都对人类文明产生了戏剧性和直接的影响。俯冲带深部流体的存在、规模和性质无疑是地震和岩浆产生的重要因素，因此必须加以识别和表征。这项研究将有助于我们目前对俯冲带深部流体的认识，并有可能建立一种新的研究方法。正如标题所示，它还将重新定义湿俯冲和干俯冲的概念，这可能会为研究俯冲带过程的其他想法和方法打开大门。该项目将为不同的研究生和本科生群体提供培训和研究机会。在当地GK-12学校的外展活动将使潜在的未来科学家接触尖端地球科学。被洋壳包围的少量陆壳可能被俯冲到超高压(UHP)深度，并在造山作用的早期阶段被挖掘出来。这些小的大陆地壳俯冲地块可以保存大规模、深俯冲流体交代作用的证据。这个团队假设，位于喜马拉雅西北部的一个年轻的超高压地体Tso Morari地体代表了一个早期俯冲的小型陆块，很可能在俯冲带的超高压阶段经历了交代作用。最近的进展导致了新的同位素和地球化学替代物的指纹，以确定俯冲来源的流体和熔体的来源，无论是在折返的俯冲物质中还是在弧形岩浆中。特别是，硼预计在脱挥发流体中富集，而在相应的寄主岩石中亏损，其同位素值提供了脱挥发程度的灵敏指示。此外，铁同位素系统学正在成为板片流体性质的潜在强大示踪剂。该项目将把这些新的替代物与更成熟的和传统的俯冲流体示踪剂结合起来，包括氧同位素、热力学和流体模拟、块状岩石地球化学、一套超高压岩石和相关蛇绿岩/混杂岩上的铁/铁铁比率。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。

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.