Archean continental weathering: Revisiting the Sr isotope seawater curve

这项授予威斯康星大学麦迪逊分校的奖项将帮助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，可能会颠覆旧的和不受约束的范式。这一提议将解决早在215亿年前的太古宙的一些非常重要的问题：板块构造何时开始，大陆地壳形成的速度有多快，它是否以幕的形式出现，这如何影响生命的演化，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建造的出现和背景？由专家开发的一套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参观。这项工作将对板块构造的开始日期和横向构造过程的作用提供基本限制。对太古宙碳酸盐岩认识的加深，将直接影响到铁矿石的主要来源--带状铁建造的发育。这项工作将限制太古代地形和高度学(平坦的地球/水世界场景)。支持者们将通过观察七套极具特征的海相碳酸盐岩来完善现有的过于简单的太古宙87锶/86锶海水曲线。这是一次认真的尝试，试图了解锶在太古代海水中的停留时间，以及这种停留时间是如何由于地幔和大陆来源的变化而发生变化的。任何新的太古宙海水87Sr/86Sr曲线都将有助于解决太古代铁建造和碳酸盐是否沉积在受限盆地和开阔海洋中的争论，并限制太古宙硅质陆相物质的亚区域风化通量，从而对我们对太古宙地球化学的理解产生真正的变革作用。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来源和程度以及太古代海水的氧化状态，并在NASA的资助下使用C、O、Mg、Fe和Mo同位素对相同的样品进行研究。这项工作是美国国家科学基金会和美国宇航局在早期地球上的机构间合作。

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.