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

前寒武纪地磁场的长期历史和特征是认识早期地球动力学的起源和性质的关键，也是利用古地磁研究早期地球地质过程的先决条件。在缺乏严格的理论约束的情况下，对地磁场方向和强度的研究成为这些数据的主要来源。太古宙-元古宙边界段可能标志着固体内核的初始生长时间，这可能影响地球动力的能量和形态特征。通过对西澳大利亚三个基性岩浆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动力学的形态、稳定性和强度，这些岩浆套包含了世界上保存最原始的这类岩石的记录。Yilgarn克拉通~2.42 Ga的Widgiemooltha岩脉群，Pilbara克拉通~2.78 Ga的Fortescue群基性熔岩流和岩脉，以及Pilbara克拉通西部~2.92 Ga的层状基性杂岩。本研究提供了晚太古代-早元古代地球动力学的概观，包括时间平均古强度值，偶极子和非偶极子场分量的相对贡献估计，以及古纬度相关的古长期变化估计。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约束。这项工作的更广泛影响包括密歇根理工大学和耶鲁大学的教育努力，例如研究生和本科生参与工作的各个方面，包括实地援助和实验室分析，以及博士论文和高级研究项目的准备。

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.