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).

我们了解地球和太阳系其他天体古代历史的一种有效方法是通过研究行星材料的磁化强度。地球内部产生的磁场是地球的一个决定性特征，它可以保护我们免受危险的太阳粒子的侵害。当岩石形成时，它们可以将磁场的方向和强度记录为磁化强度，并且可以保存数十亿年。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）的磁化是否是行星体内部产生的长期磁场的结果，还是由撞击产生的瞬态磁场的结果。 为了解释有时在行星表面以及月球和陨石样本中观察到的神秘磁化，提出了一种过程，称为冲击剩磁。陨石撞击会产生高压，而短暂的冲击会导致在磁场存在的情况下获得新的磁化强度。这种背景为理解地球撞击盆地内的冲击磁化提供了强大的动力，这与从地球内部产生的磁场以及潜在的撞击产生的磁场的获取有关。地球上存在自然发生的冲击剩磁（SRM）的最具启发性的证据来自大约 1500 年。苏必利尔湖北部直径 30 公里的板岩群岛撞击结构，那里有普遍的磁力印记。对 SRM 采集的理解、热测时法的分析和理论框架以及 Slate 群岛撞击结构和其中记录的冲击压力的地质学的分析和理论框架的进展，使得这是检验 Slate 群岛内的二次磁化强度这一假设的绝佳时机。一个 SRM。我们还试图评估假定的冲击引起的剩磁是否与地球地球发电机场的结果一致，或者它是否可以记录瞬态冲击引起的场。逐步加热热测时法与自然剩磁的详细表征和对整个结构从高到低冲击水平的样品进行岩石磁实验相结合，将帮助我们确定磁性叠印是否是冲击的结果，或者它是否可能起源于热叠印来自与撞击相关的加热。该项目将为一名博士后研究员提供早期职业培训，并为几名本科生提供研究经验。该项目的一个外展部分是为 ChronoZoom 生成与撞击坑相关的内容。 ChronoZoom 是一个动态交互式在线数据库，允许在所有时间尺度上可视化地球历史（www.chronozoomproject.org）。