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.

由于地球复杂的地球动力学历史，其地幔已演化为成分异质性，包含几种不同的成分，这些成分共同构成了“地球化学地幔动物园”。例如，在地质时期，地球的海洋地壳循环进入地幔，引入了以下成分。与其他地幔成分不同，以确定回收成分及其在地幔熔化中的作用，地幔熔化产生当今大部分地壳、氮 (N) 和稀有气体（He、Ne、Ar、Kr、Xe）。将对来自东太平洋海隆 (EPR) 附近海山的一系列特征良好的海洋熔岩进行同位素测量，这种多同位素方法将区分 EPR 地幔中的回收地幔成分和深层来源的地幔成分。伍兹霍尔海洋研究所 (WHOI) 使用巴里实验室，这是唯一一家在极低浓度样品中测量这些气体的美国实验室，通过氮气和稀有气体的镜头对极少数海山进行了检查。同位素，因此这项研究将独特地评估回收的和深部地幔挥发性成分的性质，以及它们融入太平洋地幔的程度，以增加科学参与并提高 WHOI 世界级样本和地球化学数据的可及性。 PI Anderson 将整理和整理现有和新获得的海洋基础样本及其各自的地球化学数据，将其放入基于地图的、用户友好的网站中，该网站将扩大对 WHOI 存储库的访问，以供未来科学研究使用。并将提供一种新的可访问资源，以互动的方式分享海洋科学成果，可以纳入公共和教育推广课程。海洋岛屿和大洋中脊熔岩提供了有关地球内部如何随时间演变成分异质性影响的重要线索。诸如吸积、分异、对流、地壳发育和俯冲再循环等行星尺度过程可以利用来自大洋中脊（MOR）和地球大部分海洋岛屿的海洋熔岩来限制。洋壳形成于大洋中脊（即 EPR），其中地幔熔体与厚的或地球化学改变的地壳发生较少的分异、蚀变和相互作用（与大陆下喷发的熔岩的同位素特征不同）。 -因此，洋脊（MOR）可以揭示有关地幔随时间演化的重要信息，但是，由于洋脊的有效混合，MOR 可以稀释地幔末端成员。相比之下，远离洋脊形成的海山绕过了这种均质化，从而更好地保存了端元成分，因此，为了限制东太平洋隆起下方的地幔异质性，近EPR海山熔岩将成为研究的重点。本研究中的氮和稀有气体地幔非均质性来自地幔的海洋玄武岩玻璃保留了其源氮和稀有气体（He、Ne、Ar、Kr、 Xe）同位素在地幔、地壳和大气层之间存在系统性的变化，这使得它们成为追踪地球表面和内部相互作用的有力工具。具体而言，N 和重惰性气体（Ar、Kr、Xe）是俯冲的潜在敏感示踪剂，因为它们。很容易融入俯冲板片材料（即沉积物、蚀变洋壳、板片中的孔隙水），而 He 和 Ne 不会被回收，因此是原始深部地幔的极好示踪剂这些同位素系统将共同用于限制 EPR 附近太平洋地幔中挥发物的起源。太平洋地幔中俯冲物质和/或深部地幔成分的普遍存在可能会显着影响上地幔系统，例如温度和熔化。 ，并可能有助于深入了解远离板块边界的全球火山活动。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。