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

我们可以通过研究行星物质的磁化来了解地球和太阳系其他天体的远古历史。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伤害。当岩石形成时，它们可以记录磁场的方向和强度，作为一种磁化，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)的磁化是行星体内产生的长寿命磁场的结果，还是撞击产生的瞬变磁场的结果。作为对行星表面以及月球和陨石样品中有时观察到的神秘磁化的解释，其中一个过程被称为冲击剩余磁化。陨石撞击会导致高压，持续时间较短的冲击会导致在磁场存在的情况下获得新的磁化强度。这一背景为理解地球撞击盆地内的激波磁化提供了强大的动力，无论是与其从地球获得的S内生场还是潜在的碰撞生生场有关。地球上存在自然发生的冲击波剩余磁化(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，那里有普遍的磁性叠加。在对SRM获取、热计时的分析和理论框架以及其中记录的板岩群岛撞击结构和冲击压力的地质方面的理解方面的进展，使得现在是检验板岩群岛内的次级磁化是SRM这一假设的绝佳时机。我们还试图评估假设的冲击波诱导的剩磁是否与地球地球发电场的结果一致，或者它是否可能记录了一个瞬时的撞击感应场。阶梯加热温度计时法结合自然剩余磁化的详细特征和对整个结构中从高到低冲击级别的样品进行的岩石磁性实验，将帮助我们确定磁性叠加是冲击的结果，还是可能起源于与撞击相关的加热的热叠加。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将是为ChronoZoom生成与撞击坑有关的内容。ChronoZoom是一个动态的交互式在线数据库，它允许在所有时间尺度上可视化地球历史(www.chronosomproject t.org)。

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).