Collaborative Research: MARGINS--The Relationship Between Water, Trace Elements and Slab Dehydration Across the Mariana and Izu-Bonin Arcs

合作研究：MARGINS——马里亚纳弧和伊豆-博宁弧上的水、微量元素和板坯脱水之间的关系

• 批准号: 0646869
• 负责人: Erik Hauri
• 金额: --
• 依托单位: Carnegie Institution of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-03-01 至 2011-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0646869&HistoricalAwards=false
• 关键词: Collaborative; Research; MARGINS; Relationship; Between

Intellectual Merit. The role of water in subduction zones is largely understood based on behavior of fluid-mobile elements such as B, Ba, K, Rb and U, rather than on measurements of water directly. This is because most studies of arcs rely on data from subaerial lavas which have suffered volatile loss through degassing. Published experimental studies and melt inclusion studies across the Central American arc suggest that water is released continuously from the slab across the arc. This is contrary to the behavior of fluid mobile elements, which are progressively stripped from the slab and show systematic cross-arc changes. A fundamental aim of this study is to evaluate the release of water, trace elements, and stable isotopes of hydrogen and boron across two contrasting segments of the IBM system - the Marianas and the Izu-Bonin arcs. These sites have different dip angles and subduction rates, thus we will determine whether these physical parameters have any impact on fluid behavior during progressive dehydration. The second objective of this study is to test how well trace element and B-isotopic proxies for slab fluids track fluid delivery to IBM mantle sources, and whether D/H and B isotopes trace similar fluid release processes or whether each system uniquely traces different stages of dehydration. We propose a systematic study of volatiles (CO2, H2O, S, Cl, and F), fluid soluble elements (B, Cl, Ba, K, Rb and others) and stable isotopes (H, B) in glasses and olivine hosted melt inclusions (MIs) from submarine lavas using ion microprobe techniques. This work will be complemented by multicollector ICPMS analyses of B isotopes, as well as electron microprobe measurements of major elements. The samples include a new suite of cross-chain volcanoes from the Marianas, back-arc lavas and glasses from the Mariana Trough, and lavas from the Izu-Bonin arc and back-arc. The correlation (or lack thereof) between arc magma water contents and fluid-mobile trace elements will have an important impact on the interpretation of geochemical signatures at other subduction zones with existing trace element and isotopic data but where water contents have not yet been measured.Broader Impacts. This project will complement ongoing MI studies investigating the melting process in the Lau Basin, as well as the scientific objectives of the MARGINS Subduction Factory initiative, and will foster collaboration between scientists at five institutions in the US and Japan. The project will support a female early career scientist at Woods Hole Oceanographic Institution (WHOI). As part of a WHOI and NSF-REU summer intern programs, the PI will mentor an undergraduate student during the 2nd year of the project, introducing them to ion microprobe techniques. This work will also result introduce new analytical protocols to help revitalize the NSF-supported WHOI ion probe facility which was seriously damaged in a fire in October of 2002.

智力优势。水在俯冲带中的作用在很大程度上是基于流体活动元素如B、Ba、K、Rb和U的行为来理解的，而不是直接基于水的测量。这是因为大多数对弧的研究都依赖于通过脱气而遭受挥发性损失的陆上熔岩的数据。已发表的实验研究和横跨中美洲弧的熔体包裹体研究表明，水不断从弧板中释放。这与流体移动的元素的行为相反，流体元素逐渐从板中剥离，并显示出系统的跨弧变化。本研究的一个基本目的是评估水，微量元素和稳定同位素的氢和硼的IBM系统的两个对比部分的释放-马里亚纳群岛和伊豆-小笠原弧。这些地点具有不同的倾角和俯冲速率，因此我们将确定这些物理参数是否对进行性脱水过程中的流体行为有任何影响。本研究的第二个目的是测试如何以及微量元素和B-同位素代理板流体跟踪流体输送到IBM地幔源，以及是否D/H和B同位素跟踪类似的流体释放过程，或者是否每个系统唯一的跟踪脱水的不同阶段。本文利用离子探针技术对来自海底熔岩的玻璃和橄榄石熔融包裹体中的挥发分（CO2、H2O、S、Cl、F）、流体可溶元素（B、Cl、Ba、K、Rb等）和稳定同位素（H、B）进行了系统的研究。这项工作将由B同位素的多接收器ICPMS分析以及主要元素的电子探针测量来补充。这些样本包括来自马里亚纳群岛的一套新的跨链火山，来自马里亚纳海槽的弧后熔岩和玻璃，以及来自伊豆-小笠原弧和弧后的熔岩。弧岩浆水含量和流体流动微量元素之间的相关性（或缺乏相关性）将对解释其他俯冲带的地球化学特征产生重要影响，这些俯冲带具有现有的微量元素和同位素数据，但水含量尚未测量。该项目将补充正在进行的MI研究，调查劳盆地的融化过程，以及MARGINS俯冲工厂倡议的科学目标，并将促进美国和日本五个机构的科学家之间的合作。该项目将支持伍兹霍尔海洋研究所的一名女性早期职业科学家。作为WHOI和NSF-REU暑期实习生计划的一部分，PI将在项目的第二年指导一名本科生，向他们介绍离子微探针技术。这项工作还将导致引入新的分析协议，以帮助恢复在2002年10月的火灾中严重受损的NSF支持的WHOI离子探针设施。