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).

我们可以了解太阳系中地球和其他物体的一种强大方法是通过研究行星材料的磁化。地球内部生成的磁场是我们星球的定义特征，它使我们免受危险的太阳颗粒的影响。当岩石形成时，它们可以将磁场的方向和强度记录为可以保存数十亿年的磁化。地球和行星科学正在进行的研究试图了解地球外材料（包括月球岩石和陨石）的磁化是由行星体内内部生成的长寿命的结果，还是由影响产生的瞬态磁场。 在行星表面以及月球和陨石样品中观察到的有时神秘的磁化的解释之一，它被称为冲击磁力磁化。陨石的影响会导致高压，而短时间冲击会导致在存在磁场的情况下获得新的磁化。这种背景提供了强大的动力，以了解地球上的冲击盆地内的冲击磁化，这既与从地球内部生成的领域获得的获取以及潜在的影响生成的田地有关。地球上存在天然发生的冲击磁化（SRM）的最具暗示性证据是来自CA。直径30公里的板岩岛影响苏必利尔北部北部的结构，那里存在普遍的磁性覆盖。在对SRM采集的理解，在热能工程学的分析和理论框架中以及Slate岛的地质框架中影响了其中记录的结构和冲击压力，这使得这是测试板岩岛中二级磁化的绝佳时机。我们还试图评估推定的冲击引起的延迟是否与地球地球田场导致的遗迹是一致的，还是可以记录瞬态冲击诱导的场。在整个结构的高到低冲击水平上，对自然雷神磁化和岩石磁实验的详细表征结合在一起，将有助于我们确定磁性覆盖是冲击的结果，还是它是否可以起源于影响相关的加热是导致磁性覆盖的结果。该项目将为几位本科生的博士后研究人员和研究经验提供早期职业培训。该项目的一个外展部分是生成与Chronozoom的影响陨石坑有关的内容。 Chronozoom是一个动态的交互式在线数据库，允许在所有时间标准（www.chronozoomproject.org）上可视化地球历史记录。