MARGINS: Collaborative Research: Experimental Investigation of Water Solubility in Arc Magmas at Upper Mantle Conditions

边缘：合作研究：上地幔条件下弧岩浆水溶性的实验研究

• 批准号: 0646868
• 负责人: Erik Hauri
• 金额: $ 7.5万
• 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: 2007-02-01 至 2011-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0646868&HistoricalAwards=false
• 关键词: MARGINS; Collaborative; Research; Experimental; Investigation

Intellectual Merit. It is generally accepted that partial melting of peridotite is initiated at the base of the mantle wedge by an influx of volatiles (primarily H2O) from the subducted oceanic lithosphere. However, it is unclear whether these volatiles are transported into the mantle wedge by an aqueous fluid, a hydrous silicate melt, a supercritical phase, or some combination thereof. Further, the mechanism by which partial melting proceeds in the mantle wedge remains a matter of debate. Potential modes for melt generation at convergent margins include the development of small, low-density diapirs that rise through the wedge and partially melt due to a combination of decompression and heating or reaction between relatively cool, H2O-rich magma and hotter peridotite as the melt percolates upward through the mantle wedge. The concentration of H2O dissolved in partial melts, and its influence on liquidus temperatures, densities, viscosities and transport of melts in the mantle are critical to understanding arc magmatism. While there is an extensive body of literature relating to the solubility of H2O in silicate melts at crustal P-T conditions, such experimental data pertaining to upper mantle conditions do not exist. This reflects the difficulty of doing the relevant experiments in a solid-medium piston cylinder device. This proposal describes a new experimental approach in which the concentration of hydroxyl in a solid mineral container will be measured by ion microprobe and used as a proxy for the concentration of water in the coexisting melt. This approach obviates the need to analyze the silicate melt directly, which historically has been precluded due to rapid formation of quench crystals and volatile loss during cooling of experimental run products. Results from these experiments will provide data necessary for quantifying the flux of material from the subducted oceanic lithosphere to the mantle wedge as well as the processes involved in melt generation and transport within the mantle wedge - both of which are goals of the MARGINS Subduction Factory initiative. Further, these data will help to provide a framework for interpreting geochemical and seismic results from MARGINS Focus Sites in the Izu-Bonin-Mariana and Central American subduction systems.Broader Impacts. The proposed research will (1) advance discovery and understanding while promoting teaching, training and learning, (2) broaden participation of underrepresented groups, and (3) enhance infrastructure for research and education through the involvement of graduate students in the MIT/WHOI Joint Program, undergraduate students participating in the WHOI Summer and Minority Student Fellow programs, and a female Postdoctoral Fellow at DTM. The post-doc will spend time at WHOI learning experimental techniques and will help WHOI implement SIMS analytical techniques that have been developed at DTM.

智力优点。人们普遍认为，橄榄岩的部分融化是通过从俯冲的海洋岩石圈中的挥发物（主要是H2O）涌入地幔楔的底部。但是，目前尚不清楚这些挥发物是通过水性流体，含水硅酸盐熔体，超临界相还是某种组合将这些挥发物传输到地幔楔中。此外，在地幔楔中进行部分熔化的机制仍然是辩论的问题。在收敛边缘熔融产生的潜在模式包括由于减压和加热或相对较酷的，富含H2O的岩浆和热的橄榄石作为熔体的组合而导致的小型低密度钻孔的发展，并通过楔形和部分融化而产生部分融化。通过地幔楔向上渗入。 H2O的浓度部分溶解在部分熔体中，其对液体温度，密度，粘度和地幔中熔体的运输的影响对于理解弧岩岩岩是至关重要的。尽管在地壳P-T条件下H2O在硅酸盐融化中的溶解度有关的文献广泛，但这些与上地幔条件有关的实验数据不存在。这反映了在实心活塞缸设备中进行相关实验的困难。该建议描述了一种新的实验方法，其中将通过离子微探针测量固体矿物容器中的羟基浓度，并用作共存熔体中水浓度的代理。这种方法避免了直接分析硅酸盐熔体的需求，由于淬火晶体的快速形成和实验运行产物冷却过程中的挥发性损失，历史上已经排除了硅酸盐熔体。这些实验的结果将提供必要的数据，以量化从俯冲的海洋岩石圈到地幔楔的材料通量，以及在地幔楔内融化和运输所涉及的过程 - 这两个都是边缘俯冲厂的目标的目标。此外，这些数据将有助于提供一个框架，以解释Izu-Bonin-Mariana和中美洲俯冲系统中利润率的地球化学和地震结果。拟议的研究将（1）在促进教学，培训和学习的同时提高发现和理解，（2）扩大代表性不足的群体的参与，以及（3）通过研究生参与MIT/WHOI联合的参与来增强研究和教育的基础设施课程，本科生参加WHOI夏季和少数族裔学生会计划，以及DTM的女性博士后研究员。 DOC将在W​​HOI学习实验技术上花费时间，并将帮助Whoi实施DTM开发的SIMS分析技术。