Archean continental weathering: Revisiting the Sr isotope seawater curve

太古代大陆风化：重温锶同位素海水曲线

• 批准号: 1523697
• 负责人: Clark Johnson
• 金额: $ 21.87万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-15 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1523697&HistoricalAwards=false
• 关键词: Archean; continental; weathering; Revisiting; Sr

This award to the University of Wisconsin Madison will help us understand the early Earth and the chemical characteristics of Earth's early oceans. It is interdisciplinary, and could turn over old and ill-constrained paradigms. This proposal will address some very important questions from the Archaean, earlier than 2-1/2 billion years ago: when did plate tectonics begin, how quickly was continental crust built up, did it occur in episodes, how did this affect evolution of life, and how did the emerging continents and their on-board life affect ocean chemistry and the appearance and setting of banded iron formations? Sets of K-12 educational material developed by specialists will be disseminated through the NSF-funded Portal to the Public, and the research results will be used to design and develop illustrations of 'Archean Worlds,' which will be incorporated into tours of the Madison Geology Museum.The work will provide fundamental constraints on the starting date for plate tectonics and the role of lateral tectonic processes. The enhanced understanding of Archean carbonates will bear directly upon the development of banded iron formations, the chief source of iron ore. This work will constrain Archaean topography and hypsometry (the Flat Earth/Water World scenarios). The proponents will refine the existing overly simplistic 87Sr/86Sr Archean seawater curve by looking at seven suites of extremely well characterized marine carbonates. This is a serious attempt at understanding the residence time of Sr in Archaean seawater, and how this may have changed due to changes in the mantle and continental sources. Any new seawater 87Sr/86Sr curve for the Archaean would have a truly transformative effect on our understanding of Archean geochemistry by helping to settle the controversy on whether iron formations and carbonates in the Archean were deposited in restricted basins vs. open ocean, as well as constraining Archaean subareal weathering fluxes of silicic continental material. The project will also use REE+Y systematics to deal with the origin and extent of hydrothermal input vs. continental weathering as well as the oxidation state of Archaean seawater, and perform work on the same samples with C, O, Mg, Fe, and Mo isotopes with funding from NASA.This work is a NSF-NASA inter-agency collaboration on Early Earth.

这个奖项授予威斯康星州麦迪逊大学将有助于我们了解早期地球和地球早期海洋的化学特征。它是跨学科的，可以颠覆旧的和不受约束的范式。这一提议将解决早于25亿年前的一些非常重要的问题：板块构造何时开始，大陆地壳的形成有多快，它是否发生在片段中，这如何影响生命的进化，以及新兴大陆及其船上的生命如何影响海洋化学和带状铁地层的外观和设置？由专家开发的K-12教育材料将通过NSF资助的门户网站向公众传播，研究成果将用于设计和开发“太古代世界”的插图，这些插图将被纳入麦迪逊地质博物馆的图尔斯之旅。这项工作将为板块构造的起始日期和横向构造过程的作用提供基本的限制。对太古代碳酸盐岩认识的提高，将直接影响到铁矿石主要来源--条带状铁建造的发育。这项工作将限制地球的地形和高度测量（平坦地球/水世界情景）。支持者将通过观察七套特征非常好的海洋碳酸盐来完善现有过于简单的87 Sr/86 Sr太古代海水曲线。这是一个认真的尝试，了解锶在南海海水中的停留时间，以及这可能会改变由于地幔和大陆来源的变化。任何新的海水87 Sr/86 Sr曲线将有助于解决有关太古代铁建造和碳酸盐沉积在有限盆地还是开阔洋的争议，并限制太古代陆下物质的风化通量，从而对我们对太古代地球化学的理解产生真正的变革性影响。该项目还将使用REE+Y系统学来处理热液输入与大陆风化的起源和程度以及西太平洋海水的氧化状态，并在NASA的资助下对相同的样品进行C，O，Mg，Fe和Mo同位素的工作。这项工作是NSF-NASA早期地球机构间合作。