Variations in redox of Hawaiian magmas: source and process

夏威夷岩浆氧化还原的变化：来源和过程

• 批准号: 2247717
• 负责人: Maryjo Brounce
• 金额: $ 38.81万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-06-01 至 2026-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2247717&HistoricalAwards=false
• 关键词: Variations; redox; Hawaiian; magmas; source

Lavas that erupt in Hawaii, far from the boundaries between tectonic plates, have a parameter known as the oxidation state with a large range of values. The oxidation state of some Hawaii lavas are like lavas erupted at mid-ocean ridges, where new ocean crust forms. Other Hawaii lavas are more like lavas erupted at subduction zones where ocean crust descends into the mantle. This project will investigate whether these differences are because of volcanic processes occurring in the crust at the Hawaii volcanos, or because of differences in the source material deep in the mantle. The results will have implications for plate tectonic and mantle convection processes. Broader impacts include support for a female principal investigator, a nontraditional PhD student, and undergraduate students at a federally designated Hispanic- and Asian and Pacific Islander-serving institution. Recent geological application of a new synchrotron-source analytical tool – X-ray absorption near edge structure spectroscopy – permits precise in situ measurements of Fe3+/Fe2+ and S6+/S2- ratios in basaltic glasses. With this new tool, the effects of igneous differentiation processes on these ratios in basaltic magmas and the oxygen fugacity of these magmas can now be directly quantified and corrected for in the quest to characterize the composition of the mantle from measurements of seafloor basalts. As a result, there is substantial renewed interest in re-examining fundamental questions: Is the upper mantle homogeneous or heterogeneous in its oxidation state? What are the implications of the homo/heterogeneity of this oxidation state of the mantle for plate tectonics, Earth formation, and whole-Earth differentiation? In a carefully assembled suite of samples from the Hawaiian islands that are previously studied for major, trace, and volatile element compositions as well as stable and radiogenic isotopic compositions, new measurements will be used to assess the origins of the oxidized nature of a wide variety of Hawaiian intraplate magmas. This work will determine the extent to which plate tectonic cycling may (or may not) drive a whole-Earth oxygen cycle. This project will support the research of two University of California at Riverside (UCR) undergraduate students and a UCR graduate student. These students will work towards the science goals of this proposal, as well as to work with the Natural History Museum in the Department of Earth and Planetary Sciences at UCR to rescue geologic samples at high risk of loss and which are relevant to this research proposal in the context of understanding the heterogeneous nature of the Earth’s upper mantle.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在夏威夷喷发的熔岩，远离构造板块之间的边界，有一个被称为氧化态的参数，它的值范围很大。一些夏威夷熔岩的氧化状态就像在海洋中脊喷发的熔岩，在那里形成了新的海洋地壳。其他夏威夷熔岩更像是在海洋地壳下降到地幔的俯冲带喷发的熔岩。该项目将调查这些差异是由于夏威夷火山地壳中发生的火山过程，还是由于地幔深处源物质的差异。研究结果将对板块构造和地幔对流过程产生影响。更广泛的影响包括支持一名女性首席研究员，一名非传统博士生，以及联邦政府指定的西班牙裔、亚裔和太平洋岛民服务机构的本科生。最近，一种新的同步辐射源分析工具——x射线吸收近边缘结构光谱学——在地质上的应用，使玄武岩玻璃中Fe3+/Fe2+和S6+/S2-比值的原位精确测量成为可能。有了这个新工具，火成岩分异过程对玄武岩岩浆中这些比率的影响和这些岩浆的氧逸度现在可以直接量化和校正，以便通过海底玄武岩的测量来表征地幔的组成。因此，人们对重新审视一些基本问题产生了浓厚的兴趣：上地幔的氧化态是均匀的还是非均匀的？这种地幔氧化态的同质性/非均质性对板块构造、地球形成和整个地球分化有什么意义？在夏威夷群岛精心组装的一套样品中，以前研究了主要、痕量和挥发性元素组成以及稳定和放射性成因同位素组成，新的测量方法将用于评估各种夏威夷板内岩浆氧化性质的起源。这项工作将决定板块构造循环在多大程度上可能（或不可能）驱动整个地球的氧气循环。该项目将支持加州大学河滨分校的两名本科生和一名研究生的研究。这些学生将努力实现本提案的科学目标，并与UCR地球与行星科学系的自然历史博物馆合作，在了解地球上地幔异质性的背景下，拯救与本研究提案相关的高风险地质样本。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。