Quantifying Geochemical Exchange at the Slab-Wedge Interface with Experiments and Natural Samples

通过实验和天然样品量化板楔界面处的地球化学交换

• 批准号: 1447342
• 负责人: Christy Till
• 金额: $ 27.52万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-05-01 至 2020-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1447342&HistoricalAwards=false
• 关键词: Quantifying; Geochemical; Exchange; Slab; Wedge

Abstract for Proposal 1447342 Quantifying Geochemical Exchange at the Slab-Wedge Interface with Experiments and Natural SamplesPI: C. TillThe goal of this project is to better understand the chemical reactions that result when one tectonic plate sinks below another, bringing water and other chemical constituents into the Earth's interior. The project includes collaboration with Japanese colleagues and is partly supported by International Science and Engineering. This type of plate-subduction produces volcanic arcs like those in the Ring of Fire, as well as some of the largest earthquakes on Earth every year. Understanding the chemical reactions that occur as a result of subduction is ultimately important to understand why our planet has a different type of crust than the other planets in our solar system, and how the gases and magmas emitted from volcanic arcs affect the composition of the Earth's atmosphere. Although we have long understood that subduction contributes to these planet-wide processes, many questions remain about the specific chemical reactions in which the plate-derived elements react with the Earth's mantle. This lack of knowledge is largely due to the limitations of studying subduction systems from the top down and can, in part, be resolved by studying rare samples from the mantle in conjunction with high-pressure experiments as proposed here.Part 2:This project addresses three specific questions about geochemical exchange at the subducted plate- mantle interface: 1) Do hydrous minerals, in particular chlorite, form at the base of the mantle wedge and play a key role in the formation of arc magmas as hypothesized by high-pressure experiments and studies of boron isotope fractionation?, 2) Does the composition of subducted sediment melt resemble experimental predictions and subsequently react with the mantle to produce andesitic arc magmas as predicted by geochemical models?, and 3) Do subducted plate fluxes oxidize the mantle as debated by geochemical studies of arc magmas and melt inclusions? To answer these questions we propose in-situ analyses of the major and trace element, Fe3+/FeT, and boron isotopic composition of rare peridotite and eclogite minerals from the Higashi-akaishi ultramafic complex, Japan, which represent restites and trapped melts exhumed from the base of the mantle wedge. The whole rock and mineral chemistry data will also be used to constrain starting compositions for high-pressure experiments on sediment melt-mantle wedge reactions in a complimentary effort to the in-situ chemical and isotopic analyses.

摘要提案1447342量化地球化学交换在板楔界面与实验和自然样品PI：C。这个项目的目标是更好地理解当一个构造板块下沉到另一个构造板块之下时所产生的化学反应，将水和其他化学成分带入地球内部。该项目包括与日本同事的合作，并得到国际科学与工程的部分支持。这种类型的板块俯冲产生了火山弧，就像在火环中一样，以及地球上每年最大的地震。 了解俯冲过程中发生的化学反应对于理解为什么我们的星球与太阳系中的其他行星有不同类型的地壳以及火山弧释放的气体和岩浆如何影响地球大气层的组成至关重要。 虽然我们早就知道俯冲作用有助于这些行星范围的过程，但关于板块衍生元素与地球地幔反应的具体化学反应仍然存在许多问题。 这种知识的缺乏主要是由于自上而下研究俯冲系统的局限性，部分可以通过研究地幔中的稀有样品并结合本文提出的高压实验来解决。第二部分：本项目解决俯冲板块-地幔界面地球化学交换的三个具体问题：（1）高压实验和硼同位素分馏研究所假设的，含水矿物，特别是碳酸盐矿物，是否形成于地幔楔底部，并在弧岩浆的形成中起关键作用？2)俯冲沉积物熔体的成分是否与实验预测相似，并随后与地幔反应产生地球化学模型预测的安山质弧岩浆？，3）俯冲板块的流体是否像弧岩浆和熔融包裹体的地球化学研究所争论的那样氧化了地幔？为了回答这些问题，我们提出了原位分析的主要和微量元素，Fe 3 +/FeT，和稀有橄榄岩和榴辉岩矿物的硼同位素组成的东赤石超镁铁杂岩，日本，这代表restites和被困熔体从地幔楔的基础上发掘出来。 整个岩石和矿物化学数据也将被用来限制沉积物熔体地幔楔反应的高压实验的起始成分，以补充现场化学和同位素分析。