Variations in redox of Hawaiian magmas: source and process

在远离构造板块边界的夏威夷喷发的熔岩有一个被称为氧化态的参数，其值的范围很大。某些夏威夷熔岩的氧化状态就像是在新的洋壳形成的洋中脊喷发的熔岩。其他的夏威夷熔岩更像是在俯冲带喷发的熔岩，在那里海洋地壳下降到地幔中。本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作用，还是由于地幔深处源物质的差异。研究结果对板块构造和地幔对流过程具有重要意义。更广泛的影响包括支持一名女性首席研究员，一名非传统的博士生，以及联邦指定的西班牙裔和亚洲及太平洋岛民服务机构的本科生。一种新的同步辐射源分析工具-X射线吸收近边结构光谱学-最近的地质应用允许在玄武岩玻璃中精确地原位测量Fe 3 +/Fe 2+和S6+/S2-比率。有了这个新的工具，火成分异过程对玄武岩浆中的这些比率和这些岩浆的氧逸度的影响现在可以直接量化和校正，以便从海底玄武岩的测量中表征地幔的组成。因此，重新审视基本问题的兴趣重新燃起：上地幔的氧化态是均匀的还是不均匀的？地幔氧化态的同质/异质性对板块构造、地球形成和整个地球的分异有什么意义？在一个精心组装的样品套从夏威夷群岛，以前研究的主要，微量和挥发性元素成分以及稳定和放射性同位素组成，新的测量将被用来评估各种各样的夏威夷板内岩浆的氧化性质的起源。这项工作将确定板块构造循环可能（或可能不）驱动整个地球氧气循环的程度。该项目将支持两名加州大学滨江分校（UCR）的本科生和一名UCR研究生的研究。这些学生将努力实现本提案的科学目标，以及与加州大学河滨分校地球与行星科学系自然历史博物馆合作，在高风险的情况下抢救地质样本，这些样本与了解地球上地幔的异质性有关。该奖项反映了NSF的法定使命，并被认为值得支持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。

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.