Morphology, Stability and Paleointensity of the Early Geomagnetic Field as Recorded by 2.9-2.4 Ga Mafic Rocks in Western Australia

西澳大利亚 2.9-2.4 Ga 镁铁质岩石记录的早期地磁场的形态、稳定性和古强度

• 批准号: 0711453
• 负责人: Aleksey Smirnov
• 金额: --
• 依托单位: Michigan Technological University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-10-01 至 2010-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711453&HistoricalAwards=false
• 关键词: Morphology; Stability; Paleointensity; Early; Geomagnetic

Data on the long-term history and characteristics of geomagnetic field in the Precambrian are crucial for understanding the origin and nature of the early Earth's geodynamo and as a prerequisite for using paleomagnetism to study the geological processes of the early Earth. In the absence of strict theoretical constraints, study of the direction and strength of the geomagnetic field becomes a principal source of these data. The Archean-Proterozoic boundary interval is of special interest because it may mark the time of initial growth of the solid inner core, which may have affected the energetic and morphological characteristics of the geodynamo. The morphology, stability, and strength of the Late Archean and Early Proterozoic geodynamo are investigated by detailed paleodirectional and paleointensity analyses of three mafic magmatic suites in Western Australia, which contains the world's most pristinely preserved record of such rocks through the time interval under consideration: ~2.42 Ga Widgiemooltha dike swarm in the Yilgarn craton, ~2.78 Ga mafic lava flows and dikes of the Fortescue group of the Pilbara craton, and ~2.92 Ga layered mafic complexes of the western Pilbara craton. This study provides a synoptic view of the Late Archean-Early Proterozoic geodynamo, including time-averaged paleointensity values, estimates of the relative contributions from dipole and non-dipole field components, and paleolatitude-dependent estimates of paleosecular variation. The study generates important constraints on models of the Earth's thermal evolution and age of inner core formation. Broader impacts of this work include educational efforts at Michigan Technological University and Yale University, such as involvement of graduate and undergraduate students in all aspects of the work including both field assistance and laboratory analyses, as well as preparation of a PhD dissertation and senior research projects.

前寒武纪地磁场的长期历史和特征对于理解早期地球的地球发电机的起源和性质至关重要，也是利用古地磁学研究早期地球地质过程的先决条件。在缺乏严格理论约束的情况下，对地磁场方向和强度的研究成为这些数据的主要来源。太古代-元古代边界间隔是特别感兴趣的，因为它可能标志着固体内核的初始生长的时间，这可能影响了地球发电机的能量和形态特征。通过对西澳大利亚三个镁铁质岩浆岩套进行详细的古方向和古强度分析，研究了晚太古代和早元古代地球发电机的形态、稳定性和强度。Yilgarn克拉通的~2.42 Ga Widgiemooltha岩墙群、Pilbara克拉通Fortescue群的~2.78 Ga镁铁质熔岩流和岩墙以及Pilbara克拉通西部的~2.92 Ga层状镁铁质杂岩。这项研究提供了一个晚太古代-早元古代地球发电机，包括时间平均的古强度值，估计偶极和非偶极场分量的相对贡献，和古纬度依赖的估计古长期变化的天气视图。这项研究对地球热演化和内核形成年龄的模型产生了重要的限制。这项工作的更广泛的影响包括密歇根理工大学和耶鲁大学的教育工作，如研究生和本科生参与工作的各个方面，包括现场援助和实验室分析，以及博士论文和高级研究项目的准备。