CSEDI Collaborative Research: Application of Siderophile Elements to Early Earth Processes and Mantle Mixing

CSEDI合作研究：亲铁元素在早期地球过程和地幔混合中的应用

• 批准号: 1265169
• 负责人: Richard Walker
• 金额: $ 37.02万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2017-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1265169&HistoricalAwards=false
• 关键词: CSEDI; Collaborative; Research; Application; Siderophile

Siderophile elements are those chemical elements with a strong preference for metal compared to silicates. For the Earth, the abundances of these elements were strongly affected by segregation of the metallic core, and also likely affected by processes that occurred exclusively in the silicate portion of the early Earth (mantle and crust). For this project, we will conduct collaborative, synergistic research combining observations of siderophile element concentrations and isotopic compositions, with geodynamic modeling to study the origin and evolution of chemical heterogeneities in Earth's early mantle. The outcome of this work will be an improved understanding of the global processes that led to the establishment of siderophile element abundances in the mantle, as well as provide new insights to the differentiation and mixing histories of the mantle. One specific task will be to examine the petrologic and chronologic extents of 182W isotopic anomalies in terrestrial rocks. As the decay product of the short-lived 182Hf (t½ = 9 million years), variations in 182W likely reflect processes that occurred within the mantle during the first 30 million years of Earth history. Both ancient rocks, such as komatiites for which we have already identified isotopic anomalies, and modern rocks, such as mid-ocean ridge basalts, oceanic peridotites, and ocean island basalts will be examined. Complementary to this work, we will model large-scale processes, such as magma ocean crystallization, with the potential to generate mantle domains characterized by the elemental abundances and fractionations necessary to produce the observed isotopic variances. This project will involve serious contributions from undergraduate participants at the University of Maryland (UMd). As such, some of the research proposed here will help to indoctrinate budding scientists in the methods used in isotopic geochemistry and geodynamic modeling, as well as the presentation of results. The project will also involve postdocs at both institutions. The collaborative nature of the proposal, as well as the close proximity of the UMd and Carnegie Institution for Science, will allow frequent, direct interactions involving both geochemical data acquisition and geodynamic modeling of the results for the PI?s and postdocs working on this project.

亲铁元素是那些与硅酸盐相比对金属具有强烈偏好的化学元素。对于地球来说，这些元素的丰度受到金属核心偏析的强烈影响，也可能受到仅发生在早期地球硅酸盐部分（地幔和地壳）的过程的影响。在这个项目中，我们将开展协作、协同研究，将亲铁元素浓度和同位素组成的观测与地球动力学模型相结合，以研究地球早期地幔化学异质性的起源和演化。这项工作的结果将是更好地了解导致地幔中亲铁元素丰度建立的全球过程，并为地幔的分化和混合历史提供新的见解。其中一项具体任务是检查陆地岩石中 182W 同位素异常的岩石学和年代学范围。作为短命 182Hf（t½ = 900 万年）的衰变产物，182W 的变化可能反映了地球历史前 3000 万年地幔内发生的过程。我们将检查古代岩石（例如我们已经识别出同位素异常的科马提岩）和现代岩石（例如大洋中脊玄武岩、大洋橄榄岩和洋岛玄武岩）。作为这项工作的补充，我们将模拟大规模过程，例如岩浆海洋结晶，有可能产生地幔域，其特征是产生观测到的同位素差异所需的元素丰度和分馏。该项目将涉及马里兰大学 (UMd) 本科生参与者的认真贡献。因此，这里提出的一些研究将有助于向崭露头角的科学家灌输同位素地球化学和地球动力学建模中使用的方法以及结果的呈现。该项目还将涉及两个机构的博士后。该提案的协作性质，以及密西根大学和卡内基科学研究所的紧密联系，将允许参与该项目的 PI 和博士后进行频繁、直接的互动，涉及地球化学数据采集和结果的地球动力学建模。