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: 1951166
• 负责人: Celine Martin
• 金额: $ 6.19万
• 依托单位: American Museum Natural History
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-04-01 至 2024-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1951166&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.

俯冲带是我们地球的区域，构造板汇聚。这些区域是地球上最活跃的地区之一，以高火山和地震性（例如太平洋火环）表示。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回收系统。俯冲区域中发生的过程涉及来自不同来源的大量流体，这些流体改变了化学，并改变了周围岩石的组成从表面到约100 km的深度。本项目旨在更好地限制这些流体的来源和路径，及其在俯冲带过程中的作用，例如岩石 - 流体相互作用和火山主义。该项目将由属于地球科学中代表性不足的群体的教师进行，并影响纽约市地区少数派服务机构的学生。通过通过水性液体改变地幔的serpentine形式，最多包含14 wt。水的百分比，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，它代表了研究收敛板边界内水流体的来源和作用的关键矿物。基于硼（一种流体移动元件）的最新研究表明，在缝合区中发现的蛇丁替矿记录的过程主要发生在：（i）俯冲板，（ii）地幔楔，（iii）水合前臂。因此，缝合区域中的蛇纹石代表了负责来自不同来源地幔交叉质量的水性流体的最大可追踪记录。尽管在B同位素（海水和高压变质流体）方面，两个主要的流体末端成员是充分表征的，但对于这些液体如何混合，夸张和演变而随着俯冲过程中P和T的变化而言，知之甚少。这项研究的主要目的是使用B同位素和B含量来表征在缝合区收集的蛇纹石中发生的流体混合/过度印刷和二次过程。我们的研究将为俯冲过程中发生的脱水/（RE）水合过程提供更好的了解。此外，这些数据对于了解液体在触发深层地震中的作用是必要的，并且更好地限制了负责俯冲区域熔融融化的流体。该奖项反映了NSF的法定任务，并被视为值得通过评估的支持。利用基金会的知识分子和更广泛的影响审查标准。