Collaborative Research: Mantle metasomatism during serpentinization in subduction zones: Insights from in-situ boron isotopes

俯冲带是地球上构造板块汇聚的区域。这些地区是地球上地质最活跃的地区之一，表现为火山活动和地震活动的高比率（例如，环太平洋火山（Pacific Ring of Fire）它们是地球上无处不在的特征，代表了我们星球内部和外部之间最广泛的元素循环系统。俯冲带中发生的过程涉及来自不同来源的大量流体，这些流体改变了从地表到100公里深处周围岩石的化学成分和组成。本项目旨在更好地限制这些流体的来源和路径，以及它们在俯冲带过程中的作用，如岩石-流体相互作用和火山作用。该项目将由属于地球科学中代表性不足的群体的教师以及来自纽约地区少数民族服务机构的影响学生进行。%的水，使其成为俯冲带过程中流体-岩石相互作用的最重要记录之一。因此，它代表了一个关键的矿物研究的来源和作用的水流体在会聚板块边界。基于硼（一种流体移动的元素）的最新研究表明，在缝合带中发现的蛇纹岩记录的过程主要发生在：（i）俯冲板，（ii）地幔楔，（iii）水合前弧。因此，缝合带中的蛇纹岩代表了来自不同来源的地幔交代作用的含水流体的最大可追踪记录。虽然B同位素方面的两个主要流体端元（海水和高压变质流体）的特点是很好的，很少有人知道这些流体如何混合，叠加，并在俯冲过程中的P和T的变化演变。本研究的主要目的是利用B同位素和B含量来表征缝合带蛇纹岩中流体混合/叠印和次生过程。我们的研究将提供一个更好的图片的脱水/（再）水化过程中发生的俯冲。此外，这些数据对于理解流体在触发深源地震中的作用以及更好地限制俯冲带地幔熔融的流体是必要的。该奖项反映了NSF的法定使命，并通过使用基金会的知识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 are regions of our planet where tectonic plates converge. These regions are among the most geologically active on Earth, expressed by high rates of volcanism and seismicity (e.g., the Pacific Ring of Fire). They are ubiquitous features on Earth and represent the most extensive element recycling system between the interior and exterior of our planet. The processes occurring in subduction zones involve an enormous amount of fluids from different sources, which change the chemistry and alter the composition of the surrounding rocks from the surface to depths of ~100 km. The present project aims to better constrain the source(s) and paths of these fluids, as well as their role on subduction zone processes such as rock-fluid interaction and volcanism. This project will be carried out by faculty that belong to underrepresented groups in geosciences as well as impact students from a minority-serving institution in the NYC area.Serpentine forms by alteration of the mantle by aqueous fluids and contains up to 14 wt. % of water, making it one of the most important records of fluid-rock interactions in subduction zone processes. Therefore, it represents a critical mineral to study the source and role of aqueous fluids within convergent plate boundaries. Recent studies based on boron (a fluid mobile element) suggest that serpentinites found in suture zones record processes that occurred mainly in: (i) the subducting slab, (ii) the mantle wedge, (iii) the hydrated forearc. Thus, serpentinites in suture zones represent the largest trackable record of aqueous fluids responsible for mantle metasomatism from different sources. Although the two main fluid endmembers in terms of B isotopes (seawater and high-pressure metamorphic fluids) are well-characterized, little is known about how these fluids mix, overprint, and evolve with the changes in P and T during subduction. The main goal of this study is to characterize fluid mixing/overprinting and secondary processes occurring in serpentinites collected in suture zones, using B isotopes and B contents. Our study will provide a better picture of the dehydration/(re)hydration processes occurring during subduction. Additionally, these data are necessary to understand the role of fluid(s) in triggering deep earthquakes and better constrain the fluid(s) responsible for mantle melting in subduction zones.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.