Collaborative Research: Creating Earth’s earliest continents—an integrated investigation of the growth and modification of western Australia’s Pilbara Craton

合作研究：创造地球最早的大陆——对澳大利亚西部皮尔巴拉克拉通的生长和改造进行综合调查

• 批准号: 2020831
• 负责人: Jeffrey Vervoort
• 金额: $ 33.8万
• 依托单位: Washington State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2020831&HistoricalAwards=false
• 关键词: Collaborative; Research; Creating; Earth; earliest

The formation of Earth’s earliest continents is topic of significant interest in the Earth Sciences. A major issue is that rocks preserved from Earth’s earliest history are rare; there are few rocks from the first billion years of Earth’s history, and no intact rocks at all remaining from the first 500 million years. Geologists must use a very fragmental record to determine when first continental crust formed, what was it composition, and how much of it existed. This grant will support geologists to study the Earth’s oldest, unmodified fragment of a tectonic plate – the Pilbara terrane of West Australia – to address these issues. The approach is to first determine the age of the rocks through the formation of minerals, such as zircons, that act a radioactive clocks (geochronology). Once the age is known, the chemistry of the rocks can determine if they were derived from an earlier crust or extracted directly from the Earth’s mantle (geochemistry). The patterns and fabrics of these rocks (structural geology), when integrated with geochemistry and geochronology, will determine how and when the rocks were added to the crust to create these early continents. The major outcome of this work will be a better understanding of the history of the Earth’s earliest crust and the processes that formed it. The work includes student training, mentorship and support for a junior scientist (post-doctoral fellow), and international collaboration. Additionally, work with a cognitive scientist will help students envision geological processes over large time scales. The proposal will allow technique development of sophisticated geochemical and geochronologic analyses and their use in the WSU isotope laboratory by national and international visitors.This proposal seeks to address the fundamental processes of crustal formation, modification, and stabilization by examining granitic complexes—the Mt Edgar and Corunna Downs—and associated surpracrustal rocks of the 3.5 – 2.8 Ga East Pilbara terrane of West Australia, through an integrated geochronological, geochemical, and structural study. The East Pilbara terrane is one of the best-preserved examples of Paleo- to Mesoarchean crust on Earth, displaying the classic dome-and-keel pattern in which granitic complexes (domes) are surrounded by steeply dipping volcanic and volcaniclastic supracrustal lithostratigraphy (keels). Two central, interlinking questions guide our research: 1) What were the mechanisms and timing of emplacement of the granitic complexes; and 2) What were the mantle and crustal source regions for the rocks of the East Pilbara terrane. To investigate these questions, our work will focus on: 1) The geochemistry and structure of the compositionally and deformationally heterogeneous granitic dome complexes; 2) The timing, metamorphic conditions, and structure in the deformed regions of the supracrustal lithostratigraphy (“greenstone keels”); and 3) The geochemistry of the metavolcanic rocks in the supracrustal lithostratigraphy and the grantic domes, in regions of minimal deformation, to address the mantle and crustal source regions. This integrated geochemical and structural approach will provide information on first-order tectonic processes that resulted in the formation, modification, and stabilization of one of Earth’s earliest cratons and, therefore, provide important insights into the formation and preservation on some of the earliest continental crust on Earth.This project is supported by both the Petrology & Geochemistry and Tectonics programs.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.

地球最早大陆的形成是地球科学中一个重要的话题，地球最早历史中保存下来的岩石非常稀有；地球历史最初十亿年的岩石很少，而且根本没有完整的岩石。地质学家必须使用非常碎片化的记录来确定第一个大陆地壳何时形成、其成分是什么以及其存在量。这笔赠款将支持地质学家研究地球上最古老的、未经改造的碎片。解决这些问题的方法是首先通过锆石等矿物的形成来确定岩石的年龄，这些矿物充当放射性时钟（地质年代学）。众所周知，岩石的化学性质可以确定它们是源自早期的地壳还是直接从地幔中提取（地球化学）。综合起来，这些岩石的图案和结构（构造地质学）。通过地球化学和地质年代学，研究岩石如何以及何时被添加到地壳中以形成这些早期大陆。这项工作的主要成果将是更好地了解地球最早地壳的历史及其形成过程。包括学生培训、对初级科学家（博士后研究员）的指导和支持以及国际合作，此外，与认知科学家的合作将帮助学生设想大时间尺度的地质过程，该提案将允许复杂的地球化学和地质过程的技术开发。地质年代学分析和国内和国际访客在华盛顿州立大学同位素实验室中使用它们。该提案旨在通过检查花岗岩杂岩（Mt Edgar 和 Corunna Downs）以及 3.5 – 2.8 的相关超地壳岩石来解决地壳形成、改造和稳定的基本过程。通过综合地质年代学、地球化学和结构研究，西澳大利亚州的东皮尔巴拉地体是保存最完好的地体之一。地球上古至中太古代地壳的例子，显示了经典的圆顶和龙骨模式，其中花岗岩杂岩（圆顶）被陡倾的火山和火山碎屑表层岩石地层（龙骨）包围着两个相互关联的核心问题指导我们的研究：1。 ) 花岗岩杂岩的侵位机制和时间是什么；2) 岩石的地幔和地壳源区是什么？为了研究这些问题，我们的工作将集中于：1）成分和变形异质花岗岩穹顶复合体的地球化学和结构；2）表壳变形区域的时间、变质条件和结构。岩石地层学（“绿岩龙骨”）；3）表壳岩石地层中变火山岩的地球化学和花岗岩穹顶，在地球上最早的克拉通之一的形成、改造和稳定过程中，因此，为地球上一些最早的大陆地壳的形成和保存提供了重要的见解。该项目得到了岩石学和地质学研究所的支持地球化学和构造学项目。该奖项反映了通过使用基金会的智力价值和更广泛的影响审查标准进行评估，NSF 的法定使命被认为值得支持。

项目成果

The coupled Hf-Nd isotope record of the early Earth in the Pilbara Craton

皮尔巴拉克拉通早期地球的 Hf-Nd 耦合同位素记录

• DOI: 10.1016/j.epsl.2021.117139
• 发表时间: 2021-10
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Salerno, R.;Vervoort, J.;Fisher, C.;Kemp, A.;Roberts, N.
• 通讯作者: Roberts, N.

Greenstone‐Up Shear Sense at the Margin of the Mt Edgar Dome, East Pilbara Terrane: Implications for Dome and Keel Formation in the Early Earth

绿岩——东皮尔巴拉地体埃德加山穹顶边缘的上切变感应：对早期地球穹顶和龙骨形成的影响

• DOI: 10.1029/2021tc007042
• 发表时间: 2022-04
• 期刊: Tectonics
• 影响因子: 4.2
• 作者: Roberts, Nicolas M.;Tikoff, Basil;Salerno, Ross A.
• 通讯作者: Salerno, Ross A.

Constraints on the age of dome-and-keel structures in the Pilbara Craton through integrated garnet geochronology and microstructural analyses

通过综合石榴石地质年代学和微观结构分析对皮尔巴拉克拉通穹隆龙骨结构的年龄进行限制

• DOI: 10.1016/j.precamres.2023.107108
• 发表时间: 2023-08
• 期刊: Precambrian Research
• 影响因子: 3.8
• 作者: Salerno, Ross;Roberts, Nicolas;Vervoort, Jeffrey;Tikoff, Basil
• 通讯作者: Tikoff, Basil