Postdoctoral Fellowship: OCE-PRF: Constraining recycled components in the Pacific mantle using nitrogen and noble gas isotopes

博士后奖学金：OCE-PRF：使用氮气和稀有气体同位素限制太平洋地幔中的回收成分

• 批准号: 2308183
• 负责人: Molly Anderson
• 金额: $ 34.33万
• 依托单位: Woods Hole Oceanographic Institution
• 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: 2023-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2308183&HistoricalAwards=false
• 关键词: Postdoctoral; Fellowship; OCE; PRF; Constraining

Due to the complex geodynamic history of Earth, its mantle has evolved to be compositionally heterogeneous, containing several distinct components which together comprise the "geochemical mantle zoo". For example, over geologic time, Earth’s oceanic crust recycles into the mantle, introducing compositions that differ from other mantle components. To identify recycled components and their role in mantle melting that produces most of Earth’s crust today, nitrogen (N) and noble gas (He, Ne, Ar, Kr, Xe) isotopes will be measured in a suite of well-characterized oceanic lavas from seamounts near the East Pacific Rise (EPR). This multi-isotope approach will discriminate between recycled and deeply sourced mantle components in the EPR mantle. The proposed work will be completed at Woods Hole Oceanographic Institution (WHOI), using The Barry Lab, the only USA-based lab measuring these gases in extremely low concentration samples. Very few seamounts have been examined through the lens of N and noble gas isotopes, so this study will uniquely assess the nature of recycled and deep mantle volatile components, and the extent to which they are incorporated into the Pacific mantle. To increase participation in science and improve the accessibility of samples and geochemical data from WHOI’s world-class repository, PI Anderson will curate and collate existing and newly-acquired ocean basalt samples and their respective geochemical data into a map-based, user-friendly website. The website will broaden access to WHOI’s repository for future scientific research, and will provide a new accessible resource for sharing ocean science results in an interactive way that can be incorporated into public and educational outreach curriculum.Ocean island and mid-ocean ridge lavas provide important clues about how Earth’s interior has evolved compositional heterogeneities over time. The influence of planet-scale processes like accretion, differentiation, convection, development of a crust, and subduction recycling can be constrained using oceanic lavas from mid-ocean ridges (MOR) and ocean islands. Most of Earth’s oceanic crust forms at mid-ocean ridges (i.e., the EPR), where mantle melts undergo less differentiation, alteration, and interaction with thick or geochemically altered crust (unlike melts forming beneath continents). Isotopic characterization of mantle-derived lavas erupted at mid-ocean ridges (MORs) can therefore reveal important information about the evolution of Earth’s mantle over time. However, MOR can dilute mantle end members due to efficient mixing of melts beneath the ridge. By contrast, seamounts forming away from the ridge by-pass this homogenization and thus better preserve end-member compositions. Therefore, to constrain mantle heterogeneity beneath the East Pacific Rise, near-EPR seamount lavas will be the focus of N and noble gas mantle heterogeneity in this study. Mantle-derived oceanic basalt glasses preserve time-integrated volatile characteristics of their source reservoir. Nitrogen and noble gas (He, Ne, Ar, Kr, Xe) isotopes vary systematically between mantle, crustal, and atmosphere reservoirs, making them powerful tools for tracing interactions between Earth’s surface and interior. Specifically, N and heavy noble gases (Ar, Kr, Xe) are potentially sensitive tracers of subduction, because they are readily incorporated into subducting slab materials (i.e., sediments, altered oceanic crust, pore water in the slab), whereas He and Ne are not recycled and are thus excellent tracers of primordial deep mantle contributions. Together, these isotope systems will be used to constrain the origin of volatiles in the Pacific mantle near the EPR. The prevalence of subducted materials and/or deeply sourced mantle components in the Pacific mantle may significantly impact upper mantle systematics like temperature and melting, and may lend insight into global volcanic activity away from plate boundaries.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.

由于地球的复杂地球动力学历史，其地幔已演变为完全异质的，其中包含几个不同的成分，它们共同构成了“地球化学地幔动物园”。例如，在地质时代，地球的海洋壳回收到地幔中，引入了与其他地幔组件不同的组成。为了鉴定回收的组件及其在地幔融化中的作用，这会产生当今地球上大部分地壳，氮气（N）和贵重气体（HE，NE，AR，KR，KR，XE）同位素将在一套来自东太平洋上升附近的Seamounts的良好特征化的海洋熔岩中测量（EPR）。这种多同位素方法将区分EPR地幔中的可回收和深层采购的地幔组件。拟议的工作将在Woods Hole海洋学机构（WHOI）中完成，使用Barry Lab，这是唯一一家基于美国的实验室，通过N和贵族同位素的镜头进行了很少的封口测量这些气体，因此本研究将唯一地评估回收和深层挥发性组成部分的性质，并将其融合到Paciacic中。为了增加对Whoi世界一流存储库的样本和地球化学数据的可访问性的参与，Pi Anderson将策划和整理现有和新获得的海洋玄武岩样本及其各自的地球化学数据，以纳入一个基于地图的，用户友好的网站。该网站将扩大对Whoi的存储库的未来科学研究的访问权限，并将提供一种新的可访问资源来共享海洋科学的互动方式，可以将其纳入公共和教育的外展课程中。eceanIsland.ocean Island和Midecean Ridge Lavas提供了有关地球内部如何随着时间演变成分的重要线索。行星规模的过程（如增生，分化，结构，地壳的发展和俯冲回收）的影响可以使用来自中山山脊（MOR）和海洋岛的海洋熔岩来限制。地球大部分海洋壳形成了海山脊（即EPR），地幔融化的分化，改变和与地壳厚或地球化的壳相互作用较小（与在大陆下形成的熔体不同）。因此，在中山山脊（MORS）爆发地幔衍生的熔岩的同位素表征可以揭示有关地球地幔随时间变化的重要信息。但是，由于山脊下方熔体的有效混合，MOR可以稀释地幔端构件。相比之下，远离山脊的封口旁通均匀，因此可以更好地保留末端成员的组成。因此，为了限制东太平洋上升的地幔异质性，在这项研究中，近乎EPR的海山熔岩将成为N和贵重气体披风异质性的重点。地幔衍生的海洋玄武岩玻璃可保留其来源储层的时间融合的挥发性特征。氮气和高贵气体（HE，NE，AR，KR，XE）同位素在地幔，地壳和大气储层之间有系统地变化，使其成为追踪地球表面与内部之间相互作用的强大工具。具体而言，N和重型贵重气体（AR，KR，XE）是潜在的俯冲示踪剂，因为它们很容易被掺入俯冲板材料中（即沉积物，变化的海洋壳，板块中的孔隙水），而他和Ne并没有再生，因此是很棒的，并且是很棒的校园。共同使用这些同位素系统来限制EPR附近太平洋地幔中挥发物的起源。太平洋地幔中的俯冲材料和/或深度采购的地幔组件的普遍性可能会显着影响上地幔系统，例如温度和熔化，并可能对远离板界的全球火山活动深入了解。该奖项反映了NSF的法定任务，并通过评估基金会的评估来表现出珍贵的支持。