CAREER: Linking the stable isotope record of Earth's surface and interior across the Great Oxidation Event

职业：将大氧化事件期间地球表面和内部的稳定同位素记录联系起来

• 批准号: 1943629
• 负责人: Claire Bucholz
• 金额: $ 66.45万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-02-01 至 2025-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1943629&HistoricalAwards=false
• 关键词: CAREER; Linking; stable; isotope; record

Oxygen levels in Earth’s atmosphere have risen throughout its ~4.5 billion-year history in two major transitions. The first, known as the Great Oxidation Event (GOE), occurred circa 2.3-2.4 billion years ago when atmospheric oxygen levels increased to 1-10% of present day levels. This rise in oxygen levels left an indelible imprint on the sedimentary rock record through the onset of oxidative weathering and shifts in stable isotope compositions. During this same time interval, the igneous (or magmatic) rock record underwent significant chemical and isotopic changes. The proposed research will investigate whether the changes in the sedimentary and igneous rock records are linked through studying the stable isotopes of a unique suite of igneous rocks known as strongly peraluminous granites (SPGs). SPGs form when sedimentary rocks are metamorphosed and partially melted to form granitic melts. SPGs therefore represent an endmember igneous archive of a pure sedimentary contribution (through partial melting and assimilation) to the igneous rock record. Through analyzing the isotopes of SPGs on either side of the GOE, this study will determine if and how changing sedimentary compositions affected the igneous rock record across this critical transition in Earth’s history. The PI will lead an integrated research and education plan designed to encourage participation and retention of under-represented minorities in OFW-based research through a multi-tiered mentoring system. This project supports one female or minority graduate student at Caltech, 3 undergraduate summer fellows, 3 high-school student and teacher interns from the Pasadena Unified School District (PUSD), and annual classroom lessons and field trips for PUSD middle schoolers to the local San Gabriel Mountains. The proposed research in this CAREER project will explore how the GOE influenced the O, S, and Fe isotope record of igneous rocks through partial melting or assimilation of sediments. The research examines Archean and Proterozoic strongly peraluminous granites, which represent pure partial melts of metasedimentary rocks. This research has three main objectives. First, it will shed light on the underlying causes for shifts observed in the stable isotope record of igneous rocks across the GOE. For example, the increase in O isotope ratios in magmatic zircon has been variably ascribed to the onset of plate tectonics and recycling of sedimentary rocks or to the rise of oxidative, subaerial weathering generating heavier O isotope ratios in sediments. If the latter is true, a shift in the oxygen isotope ratios of zircon from Archean and Proterozoic SPGs should be observed. Second, this research will explore in detail how Fe and S isotopes are transferred from sediments to igneous rocks through detailed field studies of two “focus” localities which preserved representative source metasedimentary rocks, as well as, the derivative SPG. Third, the SPGs provide an alternative archive to the sedimentary record in that they homogenize large volumes of sedimentary rocks and thus can yield information on average sedimentary compositions. Importantly, this work will establish a “reference collection” of SPGs, which will be curated at Caltech and made available to external researchers to investigate other aspects of their chemistry.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.

在两次主要过渡中，地球大气中的氧气水平在其45亿年的历史中升高。第一个被称为大氧化事件（GOE），发生在大约2.3-24亿年前，当时大气中的氧气水平增加到当天水平的1-10％。通过氧化风化的发作和稳定同位素组成的变化，这种氧气水平上升在沉积岩石记录上留下了难以置信的印记。在同一时间间隔内，火成岩（或岩浆）岩石记录发生了重大的化学和同位素变化。拟议的研究将研究沉积物和火成岩记录的变化是否通过研究独特的火成岩岩石套件的稳定同位素有联系，称为强烈的花岗岩（SPGS）。当沉积岩变形并部分融化为花岗岩时，SPG形成。因此，SPG代表了对火成岩记录的纯沉积物贡献（通过部分熔化和同化）的末日火成岩档案。通过分析GOE两侧的SPG的同位素，这项研究将确定是否以及如何改变沉积物成分影响地球历史上这一关键过渡的火成岩记录。 PI将领导一项综合的研究和教育计划，旨在通过多层心理系统鼓励和保留代表性不足的少数群体在基于OFW的研究中。该项目支持加州理工学院的一名女或少数族裔学生，3名本科夏季研究员，3名高中生和来自帕萨迪纳统一学区（PUSD）的教师实习生，以及PUSD中学生到当地圣加布里埃尔山的年度课堂课和实地考察。该职业项目中提出的研究将探讨GOE如何通过部分融化或同化沉积物来影响火成岩岩石的O，S和Fe同位素记录。该研究考试大将和植物学强烈的花岗岩，代表了沉积物岩石的纯部分融化。这项研究具有三个主要目标。首先，它将揭示在稳定的同位素记录中观察到的偏移的基本原因。例如，岩浆锆石中的O同位素比的增加已被多样化归因于板块构造的发作和沉积岩的回收或氧化物的崛起，即在沉积物中产生较重的O同位素比。如果后者是正确的，则应观察到来自Archean和proteroyoic SPG的锆石的氧同位素比的变化。其次，这项研究将详细探讨Fe和S同位素如何通过对两个“焦点”所在地的详细现场研究将保存代表性源的沉积物以及导数SPG传递到火成岩。第三，SPG为沉积记录提供了替代档案，因为它们使大量的沉积岩均匀，因此可以产生平均沉积物成分的信息。重要的是，这项工作将建立SPGS的“参考收集”，该奖项将在Caltech策划，并提供给外部研究人员，以调查其化学的其他方面。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛的影响审查标准通过评估来获得的支持。

项目成果

Sulfur isotope behavior during metamorphism and anatexis of Archean sedimentary rocks: A case study from the Ghost Lake batholith, Ontario, Canada

• DOI: 10.1016/j.epsl.2020.116494
• 发表时间: 2020-11
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: C. Bucholz;J. Biasi;P. Beaudry;S. Ono

Emergence of continents above sea‐level influences sediment melt composition

• DOI: 10.1111/ter.12531
• 发表时间: 2021-04
• 期刊: Terra Nova
• 影响因子: 2.4
• 作者: J. Liebmann;C. J. Spencer;C. Kirkland;C. Bucholz;X. He;M. Santosh;X. Xia;Martín L.;N. Evans

Coupling sulfur and oxygen isotope ratios in sediment melts across the Archean-Proterozoic transition

• DOI: 10.1016/j.gca.2021.05.045
• 发表时间: 2021-05
• 期刊: Geochimica et Cosmochimica Acta
• 影响因子: 5
• 作者: J. Liebmann;C. Spencer;C. Kirkland;C. Bucholz;X. Xia;L. Martin;N. Kitchen;L. Shumlyanskyy

Secular variability in zircon phosphorus concentrations prevents simple petrogenetic classification

锆石磷浓度的长期变化阻碍了简单的岩石成因分类

• DOI: 10.7185/geochemlet.2240
• 发表时间: 2022
• 期刊: Geochemical Perspectives Letters
• 影响因子: 4.9
• 作者: Bucholz, C.;Liebmann, J.;Spencer, C.J.
• 通讯作者: Spencer, C.J.

Coevolution of sedimentary and strongly peraluminous granite phosphorus records

• DOI: 10.1016/j.epsl.2022.117795
• 发表时间: 2022-09-09
• 期刊: EARTH AND PLANETARY SCIENCE LETTERS
• 影响因子: 5.3
• 作者: Bucholz, Claire E.