Archean continental weathering: Revisiting the Sr isotope seawater curve

威斯康星大学麦迪逊分校获得的这个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25亿年前的太古宙的一些非常重要的问题：板块构造是什么时候开始的？大陆地壳形成的速度有多快？它是分阶段发生的吗？这是如何影响生命的进化的？新兴的大陆及其船上的生命是如何影响海洋化学的？以及带状铁构造的出现和形成的？由专家开发的K-12教育材料将通过美国国家科学基金会资助的公众门户网站传播，研究结果将用于设计和制作“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中。这项工作将为板块构造的开始日期和侧向构造过程的作用提供基本约束。对太古宙碳酸盐岩的进一步了解将直接影响到带状铁地层的发育，这是铁矿石的主要来源。这项工作将限制太古宙地形和假设（平坦地球/水世界情景）。支持者将通过观察7组特征非常明显的海洋碳酸盐岩，来完善现有过于简单的87Sr/86Sr太古宙海水曲线。这是一次认真的尝试，旨在了解Sr在太古宙海水中的停留时间，以及由于地幔和大陆源的变化，Sr在太古宙海水中的停留时间是如何变化的。任何新的太古宙海水87Sr/86Sr曲线都将对我们对太古宙地球化学的理解产生真正的革命性影响，因为它有助于解决太古宙铁地层和碳酸盐沉积于封闭盆地还是开放海洋的争议，以及限制太古宙硅大陆物质的亚区域风化通量。该项目还将使用REE+Y系统来处理热液输入与大陆风化的起源和程度，以及太古海水的氧化状态，并在NASA的资助下对相同样品进行C， O, Mg， Fe和Mo同位素的研究。这项工作是nsf和nasa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.