Collaborative Research: Testing the shock remanent magnetization hypothesis in the Slate Island impact structure

合作研究：测试石板岛撞击结构中的冲击剩磁假说

• 批准号: 1316375
• 负责人: David Shuster
• 金额: $ 16.18万
• 依托单位: Berkeley Geochronology Center
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1316375&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; shock; remanent

One powerful way we can learn about the ancient history of Earth and other bodies in the solar system is through study of the magnetization of planetary materials. Earth's internally-generated magnetic field is a defining characteristic of our planet that shields us from dangerous solar particles. When rocks form, they can record both the direction and strength of magnetic fields as a magnetization that can be preserved for potentially billions of years. Ongoing research in the Earth and planetary sciences seeks to understand whether the magnetization of extraterrestrial materials (including lunar rocks and meteorites) are the result of long-lived fields internally-generated by planetary bodies, or transient magnetic fields generated by impacts. One of the processes advanced as an explanation of sometimes enigmatic magnetizations observed on planetary surfaces, as well as in lunar and meteorite samples, is known as shock remanent magnetization. Meteorite impacts lead to high pressures and the short duration shock can lead to the acquisition of new magnetization in the presence of a magnetic field. This context provides strong motivation to understand shock magnetization within impact basins on Earth both in relation to its acquisition from Earth?s internally-generated field as well as potential impact-generated fields. The most suggestive evidence for the presence of naturally occurring shock remanent magnetization (SRM) on Earth is from the ca. 30 km diameter Slate Islands impact structure in northern Lake Superior where there is a pervasive magnetic overprint. Advances in the understanding of SRM acquisition, in the analytical and theoretical framework of thermochronometry and of the geology of the Slate Islands impact structure and shock pressures recorded therein, make this an excellent time to test the hypothesis that the secondary magnetization within the Slate Islands is an SRM. We also seek to evaluate whether the putative shock-induced remanence is consistent with resulting from the Earth's geodynamo field or if it may record a transient impact-induced field. Stepped heating thermochronometry combined with detailed characterization of natural remanent magnetization and rock magnetic experiments on samples from high to low shock levels across the structure will help us determine if the magnetic overprint is the result of shock, or whether it could have originated as a thermal overprint from impact-related heating. This project will provide early-career training for a postdoctoral researcher and research experience for several undergraduate students. An outreach component of this project will be to generate content related to impact craters for ChronoZoom. ChronoZoom is a dynamic interactive online database that allows for the visualization of Earth history on all timescales (www.chronozoomproject.org).

我们可以了解地球和太阳系其他天体的古代历史的一个强有力的方法是通过研究行星材料的磁化。地球内部产生的磁场是地球的一个决定性特征，它保护我们免受危险的太阳粒子的伤害。当岩石形成时，它们可以记录磁场的方向和强度，作为可以保存数十亿年的磁化强度。地球和行星科学正在进行的研究旨在了解地外物质（包括月球岩石和陨石）的磁化是行星内部产生的长期磁场的结果，还是撞击产生的瞬态磁场。 在行星表面以及月球和陨石样本中观察到的有时神秘的磁化过程中，有一个过程被称为冲击反射磁化。陨石撞击导致高压，短时间冲击可导致在磁场存在下获得新的磁化。这一背景下提供了强大的动机，以了解冲击磁化内的影响盆地在地球上，无论是在其收购从地球？的内部产生的领域，以及潜在的影响产生的领域。地球上存在自然发生的冲击回复磁化（SRM）的最有启发性的证据是来自ca。上级湖北方直径30公里的板岩岛撞击结构，其中有一个普遍的磁性叠加。在对SRM采集的理解、热年代学的分析和理论框架以及板岩群岛撞击结构的地质和其中记录的冲击压力方面的进展，使这成为检验板岩群岛内的二次磁化是SRM这一假设的绝佳时机。我们还试图评估是否假定的冲击引起的剩磁是一致的，从地球的地球发电机领域，或者如果它可能会记录一个短暂的冲击引起的领域。步进加热热年代测定法结合天然反射磁化和岩石磁性实验的样品从高到低冲击水平的结构的详细表征，将帮助我们确定是否磁叠印是冲击的结果，或者它是否可能起源于从冲击相关的加热热叠印。该项目将为一名博士后研究人员提供早期职业培训，并为几名本科生提供研究经验。该项目的一个外联部分将是为ChronoZoom制作与撞击坑有关的内容。ChronoZoom是一个动态的交互式在线数据库，可以在所有时间尺度上可视化地球历史（www.chronozoomproject.org）。