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

合作研究：俯冲带蛇纹石化过程中的地幔交代作用：来自原位硼同位素的见解

• 批准号: 2150618
• 负责人: Kennet Flores Reyes
• 金额: $ 16.06万
• 依托单位: University of North Carolina at Chapel Hill
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2024-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2150618&HistoricalAwards=false
• 关键词: Collaborative; Research; Mantle; metasomatism; during

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.

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，表现为高火山活动和地震活动（例如太平洋火环）。它们是地球上无处不在的特征，代表了地球内部和外部之间最广泛的元素回收系统。俯冲带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约 100 公里深度的周围岩石的化学成分和成分。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（例如岩石-流体相互作用和火山作用）中的作用。该项目将由属于地球科学领域代表性不足群体的教师以及来自纽约地区少数族裔服务机构的学生进行。蛇纹石是由水性液体改变地幔而形成的，含有高达 14 重量％的元素。 ％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，它是研究会聚板块边界内水性流体的来源和作用的关键矿物。最近基于硼（一种流体移动元素）的研究表明，在缝合带中发现的蛇纹岩记录了主要发生在：（i）俯冲板片，（ii）地幔楔，（iii）水合前弧中的过程。因此，缝合带中的蛇纹岩代表了负责不同来源地幔交代作用的水流体的最大可追踪记录。尽管以B同位素表示的两种主要流体端元（海水和高压变质流体）已被充分表征，但人们对这些流体在俯冲过程中如何随着P和T的变化混合、叠印和演化知之甚少。本研究的主要目标是利用 B 同位素和 B 含量来表征缝合带收集的蛇纹岩中发生的流体混合/套印和二次过程。我们的研究将更好地描述俯冲过程中发生的脱水/（再）水化过程。此外，这些数据对于了解流体在引发深部地震中的作用以及更好地限制导致俯冲带地幔熔化的流体是必要的。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。