Hydrogen Isotope Studies of Submarine Basalts

海底玄武岩的氢同位素研究

• 批准号: 0208127
• 负责人: John Eiler
• 金额: $ 4.72万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-01 至 2003-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0208127&HistoricalAwards=false
• 关键词: Hydrogen; Isotope; Studies; Submarine; Basalts

EilerEAR-0208127Hydrogen is arguably the most important minor element in the solid earth: It dominates the melting behavior and rheology of mantle rocks; it is the principle solvent for metasomatic transport in the crust and mantle; its concentration in silicate minerals controls rates of diffusion of other elements; and its abundance in silicate melts strongly influences crystallization-differentiation. However, the geochemistry of hydrogen is less well described than that for virtually any other element (and certainly any of similar importance): Reasonable estimates of the total abundance of H in the earth span a range of nearly an order of magnitude; concentrations, residence times, and sources and sinks of hydrogen in major mantle reservoirs are poorly known or only guessed at; and partitioning of hydrogen between minerals and melts has yet to be described with the same experimental sophistication given to studies of other minor elements.We believe that our understanding of the global hydrogen cycle can be advanced by studying the hydrogen isotope composition (i.e., D/H ratio) of well characterized suites of submarine basalts whose origin and evolution is influenced by mantle hydrogen. The potential for such studies has been recognized for many years, but has not been realized due to sparse data, the large proportion of isotopic measurements on samples that are not characterized for other important geochemical parameters, and lack of inter-laboratory standardization. We propose to characterize the variation in D/H ratio among submarine basalts associated with the Mariana arc and its back arc basin, which are a key set of samples for our current understanding of the role of water in magma genesis at convergent margins. We will approach this study using a new analytical method for determining D/H ratios and H contents of small quantities (10's to hundreds of micrograms) of hydrous solids and glasses at a rate approximately 10x that of conventional analyses but with similar accuracy and precision. This method will let us produce relatively large, well standardized and well replicated data sets in a reasonable time frame.

氢可以说是固体地球中最重要的微量元素：它控制着地幔岩石的熔融行为和流变学;它是地壳和地幔中交代迁移的主要溶剂;它在硅酸盐矿物中的浓度控制着其他元素的扩散速率;它在硅酸盐熔体中的丰度强烈影响结晶分异。 然而，氢的地球化学性质比几乎任何其他元素的地球化学性质都要少（当然也有类似的重要性）：对地球中氢总丰度的合理估计跨越了近一个数量级的范围;主要地幔储层中氢的浓度、停留时间和源和汇知之甚少，或者只是猜测;氢在矿物和熔体之间的分配还有待于用与其他微量元素研究相同的实验复杂性来描述。我们相信，通过研究氢同位素组成（即，D/H比）的海底玄武岩的起源和演化的影响，地幔氢的良好特征套件。 这种研究的潜力多年来一直得到认可，但由于数据稀少、对样品进行的同位素测量大部分没有其他重要的地球化学参数，以及缺乏实验室间的标准化，因此一直没有实现。 我们建议，以表征与马里亚纳弧及其弧后盆地，这是一个关键的一组样本，我们目前的理解水在岩浆成因的作用在收敛边缘的海底玄武岩之间的D/H比的变化。 我们将使用一种新的分析方法来进行这项研究，该方法用于以约10倍于常规分析的速率测定少量（10至数百微克）含水固体和玻璃的D/H比和H含量，但具有相似的准确度和精度。 这种方法将使我们能够在合理的时间范围内产生相对较大的，标准化良好的和复制良好的数据集。