Collaborative Research: Water Concentration and Distribution in the Oceanic Lithosphere

合作研究：海洋岩石圈中的水浓度和分布

• 批准号: 1624315
• 负责人: Michael Bizimis
• 金额: $ 28.22万
• 依托单位: University of South Carolina at Columbia
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-15 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1624315&HistoricalAwards=false
• 关键词: Collaborative; Research; Water; Concentration; Distribution

The chemical compound H2O, which in its liquid state is called water, when it occurs bound in minerals and other solids, influences melting, rheology and plastic behavior of the mineral or material, and the material's thermal and electrical properties. In the case where H2O is bound in minerals deep in the ocean crust, this can result in enhanced generation of magmas, hence volcanic eruptions, and changes in the plasticity, deformation of the lithosphere. In areas where magmas rise to the surface, this H2O is released and forms an important part of the global cycle of H2O. Because most of the H2O on Earth is locked up in minerals in the crust and mantle, the concentration and distribution of H2O in various mantle and lithospheric reservoirs have been inferred primarily from analyses of undegassed glasses and melt inclusions in oceanic basalts through a comparison of their H2O content with incompatible rare earth elements like Cerium. This only provides a rough estimate of the H2O content of the Earth. This research builds off the results of a pilot study and uses a novel new approach to determine how much H2O is stored in minerals in the oceanic mantle and lithosphere, the mechanisms that fractionate H2O from other geochemical tracers in mantle lithologies, and the fate of the H2O and how it impacts the electrical conductivity and rheology of the oceanic lithosphere. Broader impacts of the work include support of a faculty member at an institution in South Carolina, an EPSCoR state (i.e., a state that does not receive significant federal funding), support of a researcher whose gender is under-represented in the sciences, and student training who will get trained on cutting-edge analytical instrumentation at NASA at the Johnson Space Center in Houston, TX. Impacts also include international collaboration with Belgian and Japanese scientists and making the data accessible to the public.Questions to be addressed by this research include seeing if H2O varies independently from lithophile elements in the lithosphere and if diffusion is responsible if decoupling is observed; looking to see if pyroxenes are typically a high-H2O, low-solidus reservoir; examine if H2O solubility in minerals under lithospheric pressures and temperatures put an upper limit on how much structurally bound H2O is held in the unaltered lithosphere; whether H2O concentrations are reflected in the H2O systematics of lithospheric samples; and whether there are systematic correlations between H2O distribution in the lithosphere and the degree of melting, depth, and lithology and metasomatic agents. To address these issues, Fourier Transform Infrared Spectroscopy (FTIR) will be used to determine the H2O concentrations in well-characterized, fresh (i.e., unaltered) peridotites and pyroxenites from a suite of locations and tectonic settings that include the Canary Islands in the Atlantic Ocean; the Kerguelen Plateau in the South Indian Ocean; the Hawaiian and Samoan Islands and the Ontong Java Plateau in the Pacific Ocean; and the Lena Trough in the Arctic Ocean. Additional geochemical indicators, such as trace element compositions of minerals and radiogenic isotopes of Sr, Hf, Nd, and Pb in minerals and rocks will be used to help determine if there is a link between process, mineralogy, and H2O content/behavior.

化学化合物H2O在其液态下被称为水，当它结合在矿物和其他固体中时，会影响矿物或材料的熔融、流变学和塑性行为，以及材料的热和电性能。 在H2O被束缚在海洋地壳深处的矿物中的情况下，这可能导致岩浆的生成增强，从而导致火山爆发，以及岩石圈塑性和变形的变化。在岩浆上升到地表的地区，这种H2O被释放出来，并形成全球H2O循环的重要组成部分。由于地球上大部分的H2O被锁在地壳和地幔的矿物中，H2O在各种地幔和岩石圈储层中的浓度和分布主要是通过对海洋玄武岩中未脱气玻璃和熔融包裹体的分析来推断的，通过将它们的H2O含量与不相容的稀土元素（如铈）进行比较。 这只是对地球上H2O含量的一个粗略估计。这项研究建立了一个试点研究的结果，并使用了一种新的方法来确定有多少H2O存储在海洋地幔和岩石圈的矿物，断裂H2O从地幔岩性中的其他地球化学示踪剂的机制，以及H2O的命运，以及它如何影响海洋岩石圈的电导率和流变性。 这项工作的更广泛影响包括支持南卡罗来纳州一所机构的一名教员，这是一个EPSCoR州（即，一个没有得到大量联邦资金的州），一名性别在科学领域代表性不足的研究人员的支持，以及将在德克萨斯州休斯顿约翰逊航天中心的美国宇航局接受尖端分析仪器培训的学生培训。影响还包括与比利时和日本科学家的国际合作，并向公众提供数据。这项研究要解决的问题包括：观察H2O是否独立于岩石圈中的亲石元素而变化，如果观察到解耦，扩散是否是原因;观察辉石是否通常是高H2O，低固相线的储层;检查在岩石圈压力和温度下矿物中H2O的溶解度是否对未改变的岩石圈中结构结合H2O的含量设置上限; H2O浓度是否反映在岩石圈样品的H2O系统学中;岩石圈中H_2O的分布与熔融程度、深度、岩性和交代剂之间是否存在系统的相关性。为了解决这些问题，傅里叶变换红外光谱（FTIR）将被用来确定H2O浓度在良好表征，新鲜（即，这些岩石来自一系列地点和构造环境，包括大西洋的加那利群岛;南印度洋的凯尔盖朗高原;太平洋的夏威夷和萨摩亚群岛和翁通爪哇高原;以及北冰洋的Lena海槽。其他地球化学指标，如矿物的微量元素成分和矿物和岩石中Sr、Hf、Nd和Pb的放射性同位素，将用于帮助确定过程、矿物学和H2O含量/行为之间是否存在联系。