The First Billion Years of the Geodynamo

地球发电机的第一个十亿年

• 批准号: 1656348
• 负责人: John Tarduno
• 金额: $ 45万
• 依托单位: University of Rochester
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-02-01 至 2021-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1656348&HistoricalAwards=false
• 关键词: First; Billion; Years; Geodynamo

Knowing when Earth's magnetic field began is important for understanding the evolution of the core, atmosphere and life on Earth. The PI team has recently reported the first measurements of Earth's ancient magnetic field as recorded in zircons- natural crystals from the Jack Hills of Western Australia that are the oldest known materials on Earth, dating to a time period known as the Hadean. Some of these zircons host magnetic inclusions capable of preserving magnetic field records for billions of years. Data from zircons between 3.3 and 4.2 billion-years-old record magnetic fields that vary in strength from those typical of the present-day field, to only about 10% of that value. The earliest Hadean geomagnetic field may have been powered by chemical precipitation (of MgO) in the core. The existence of this ancient terrestrial magnetic field implies that early atmospheric evolution was regulated by dynamo behavior. These new observations provide the basis for continued work. The investigators hope to refine the history of the first billion years of the geodynamo and to test its fidelity through field and laboratory based programs. Undergraduate and graduate student training is integrated into these programs, as is international collaboration and inter-laboratory comparison and calibration efforts.Knowing when the geodynamo started is important for understanding the evolution of the core, atmosphere and life on Earth. We have recently reported the first paleointensity measurements of Archean to Hadean zircons bearing magnetic inclusions from the Jack Hills conglomerate (Western Australia) to reconstruct the early geodynamo history. Data from zircons between 3.3 and 4.2 billion-years-old record magnetic fields varying between ¡­1.0 and 0.12 times recent equatorial field strengths. A Hadean geomagnetic field may have been powered by chemical precipitation of MgO in the core. The existence of a terrestrial magnetic field prior to the Late Heavy Bombardment is supported by terrestrial N isotopic evidence and implies that early atmospheric evolution on both Earth and Mars was regulated by dynamo behavior. These new observations provide the basis for our continued work to refine the history of the first billion years of the geodynamo and to test its fidelity.We outline 8 tasks that form the basis of our work plan: 1. Rock magnetism, anisotropy studies and full Thellier-Coe analyses of Eoarchean and Hadean zircons; 2. Imaging of magnetic inclusions in zircons; 3. Analyses of zircons from new sites in Western Australia; 4. Analyses of zircons from new sites in Zimbabwe; 5. New tests of re-heating scenarios, including studies of Li zoning; 6. Inter- lab and instrument comparisons and sample distribution; 7. Studies of terrestrial-solar interactions for the early Earth and 8. Studies of the thermal evolution of Earth¡¯s deep interior informed by our findings. Ultimately, our goal is to broadly define the first billion years of geodynamo history, after the Lunar-forming giant impact to Paleoarchean times, and to evaluate the implications of this record for the evolution of the atmosphere, mantle and core.The proposed work will support graduate students and undergraduates, who will acquire valuable skills through training in field studies and in the laboratory. Salient aspects of our undergraduate education plans, and its integration into our research, include i. field excursions for sampling in Western Australia and Zimbabwe as part of an undergraduate summer research program involving rock magnetic, paleomagnetic and electron microscope analyses and ii. undergraduate research courses leading to Senior theses. The work proposed will contribute to Ph.D. and M.S. theses. We also propose a visiting scientist program to the University of Rochester paleomagnetic laboratories, providing the opportunityfor community instruction on methods of single silicate crystal paleomagnetic analyses developed at Rochester over the last twenty years.

知道地球磁场何时开始，对于理解地球上核心，大气和生命的演变很重要。 PI团队最近报道了地球古代磁场的首次测量，如锆石所记录的 - 西澳大利亚州杰克山的天然晶体是地球上最古老的材料，其历史可追溯到被称为Hadean的时期。这些锆石中的一些含有能够保存数十亿年的磁场记录的磁性包含物。来自3.3至42亿年历史的记录磁场的数据，其强度从当今典型场的磁场变化，到该值的仅约10％。最早的Hadean地磁场可能是由核心中的化学沉淀（MGO）供电的。这个古老的陆地磁场的存在意味着早期大气进化受到发电机行为的调节。这些新观察为继续工作提供了基础。调查人员希望改善地迪纳莫最初十亿年的历史，并通过基于现场和实验室的计划来测试其忠诚度。本科生和研究生培训都融入了这些计划，国际合作和实验室间比较和校准工作也融入了。开始时，Geodynamo何时开始时对于理解地球上核心，气氛和生活的演变很重要。我们最近报道了对大将的首个古显度测量，该测量值是杰克山砾岩（西澳大利亚州）的磁性包裹物的Hadean锆石，以重建早期的Geodynamo历史。来自3.3至42亿年历史的记录磁场之间的锆石的数据在最近的等效磁场强度之间变化。 Hadean地磁场可能是由MGO在核心中的化学沉淀提供动力的。陆地n同位素证据支持在晚期重轰击之前存在陆地磁场，这意味着地球和火星上的早期大气进化受到发电机行为的调节。这些新观察为我们继续工作提供了完善地迪纳莫前十亿年历史并测试其忠诚度的历史的基础。我们概述了8个任务，构成了我们工作计划的基础：1。摇滚磁化，各向异性研究以及对Eooarchian和Hadean Zircons的全面磁疗研究； 2。锆石中磁性夹杂物的成像； 3。分析西澳大利亚州新地点的锆石； 4。津巴布韦新地点的锆石的分析； 5。重新加热方案的新测试，包括对Li Zoning的研究； 6。超级和仪器比较和样品分布； 7。对早期地球的陆生 - 极性相互作用的研究和8。关于地球的热进化的研究。最终，我们的目标是广泛定义Geodynamo历史的最初数十亿年，在对古老时代的巨大巨大影响之后，并评估了这一记录对大气，地幔和核心演变的含义。拟议的工作将支持研究生和本科生，他们将通过在实验室和实验室研究中培训有价值的技能。我们的本科教育计划的显着方面及其在我们的研究中的整合包括i。西澳大利亚州和津巴布韦进行采样的现场游览，这是一项涉及岩石磁性，古磁和电子显微镜分析和II的本科夏季研究计划的一部分。大学研究课程导致高级论文。拟议的工作将促进博士学位。和M.S.这些。我们还向罗切斯特大学古磁实验室提出了一项访问科学家计划，为过去二十年来在罗切斯特开发的单硅晶体古磁分析方法提供了社区指导的机会。

项目成果

Paleomagnetism indicates that primary magnetite in zircon records a strong Hadean geodynamo

• DOI: 10.1073/pnas.1916553117
• 发表时间: 2020-01
• 期刊: Proceedings of the National Academy of Sciences of the United States of America
• 影响因子: 11.1
• 作者: J. Tarduno;R. Cottrell;R. Bono;H. Oda;W. Davis;M. Fayek;O. V. Erve;F. Nimmo;Wentao Huang;E. Thern;S. Fearn;G. Mitra;A. V. Smirnov;E. Blackman

Cluster analysis on a sphere: Application to magnetizations from metasediments of the Jack Hills, Western Australia

• DOI: 10.1016/j.epsl.2017.12.007
• 发表时间: 2018-02-15
• 期刊: EARTH AND PLANETARY SCIENCE LETTERS
• 影响因子: 5.3
• 作者: Bono, Richard K.;Tarduno, John A.;Cottrell, Rory D.
• 通讯作者: Cottrell, Rory D.