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: 1316395
• 负责人: Nicholas Swanson-Hysell
• 金额: $ 16.32万
• 依托单位: University of California-Berkeley
• 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 2016-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1316395&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).

我们可以通过研究行星材料的磁化来了解地球和太阳系中其他天体的古代历史。地球内部产生的磁场是我们这个星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，作为磁化，可以保存数十亿年。正在进行的地球和行星科学研究试图了解地外物质（包括月球岩石和陨石）的磁化是由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。在行星表面以及月球和陨石样本中观察到的有时令人费解的磁化现象，其中一个被称为激波残余磁化的过程被提出来解释。陨石撞击导致高压，短时间的冲击可以导致在磁场存在下获得新的磁化。这一背景为理解地球上撞击盆地内的激波磁化提供了强大的动力，包括从地球上获取激波磁化。S内部产生的场以及潜在的影响产生的场。地球上存在自然发生的激波残余磁化（SRM）的最有说服力的证据来自苏必利尔湖北部直径约30公里的板岩群岛撞击结构，那里有一个普遍存在的磁叠印。在对SRM采集的理解、热时学的分析和理论框架以及Slate群岛撞击结构的地质和记录的冲击压力方面的进展，使现在成为检验Slate群岛内的次级磁化是SRM假设的绝佳时机。我们还试图评估假定的冲击诱发剩余物是否与地球地球动力场的结果一致，或者它是否可能记录一个短暂的冲击诱发场。阶梯式加热热时计结合对整个结构从高到低冲击水平样品的自然剩余磁化和岩石磁性实验的详细表征，将帮助我们确定磁套印是冲击的结果，还是可能起源于与冲击相关的加热的热套印。该项目将为一名博士后提供早期职业培训，并为几名本科生提供研究经验。该项目的一个外展组成部分将是为ChronoZoom生成与陨石坑相关的内容。ChronoZoom是一个动态的交互式在线数据库，允许在所有时间尺度上可视化地球历史（www.chronozoomproject.org）。