Investigating Earth's impact history through time using in situ high precision U-Pb dating

使用原位高精度 U-Pb 测年技术研究地球随时间的撞击历史

• 批准号: RGPIN-2019-05343
• 负责人: Kamo, Sandra
• 金额: $ 2.55万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=715501
• 关键词: Investigating; Earth; impact; history; through

Earth's early history (Hadean Eon) was affected by intense meteorite bombardment recorded on the Moon by impact basins. Dating of lunar impact melt and meteorites indicates ages ranging from ~4.2 to ~3.9 billion years old, with a preponderance towards the young end of the age spectrum. Evidence of the impacts have not survived on Earth's dynamic surface. Instead, we rely on mission-returned samples and meteorites. The precise time sequence of formation of such astro-materials can answer fundamental questions about Earth's beginnings. Did bombardment begin as a consequence of planet formation in the inner Solar System and continue throughout the Hadean? Or was it restricted to a late, intense terminal cataclysm', as commonly cited? Earth's subsequent meteorite impact history is documented by ~190 known impact structures around the world, but precise age information for these events is severely lacking. This makes it difficult to assess their influence on Earth's evolutionary past. The proposed research will investigate the meteorite impact history of Earth using uranium-lead (U-Pb) dating in combination with an innovative extraction technique to isolate minerals within their geological context. For the first time, in situ ages on Lunar and Martian meteorites, and asteroids, will be determined using the latest advances in high precision U-Pb geochronology to establish precise ages to help clarify the time span of our early bombardment history. This is fundamental in understanding how the Earth and other planets evolved, and to how and why the impact flux rate changed through time. It has implications to understanding the emergence of life, which may have been negatively affected by early intense bombardment. In the terrestrial record, meteorite impacts have left traces of their effects in the geological and biological records. The time of impact cratering can be determined on minerals that crystallized, or were isotopically reset, during the impact process. Ages are important for assessing effects on the ecosphere, and to establishing flux rates, which can have implications for human populations. At least one meteorite impact is known to have played a role in a major mass extinction at the end of the Cretaceous. Samples from impacts (e.g., Brent, Carswell, Vredefort, Chesapeake Bay, and Sudbury) are in hand and will be investigated for their timing, age of target rocks, and effects of post-impact thermal overprinting. The proposed research is a new approach and will position Canada as unique in the world. High precision in situ dating on impacts will build upon my history of impact dating. Results will advance the field of planetary evolution and help evaluate past environmental response to impacts through correlations in the stratigraphic record. It is a uniquely Canadian effort in uniting the birthplace of modern U-Pb dating and nanobeam mineral investigation with the only available instrument for micro-milling minerals.

地球的早期历史（Hadean Eon）受到冲击盆地在月球上记录的激烈的陨石轰击的影响。月球撞击熔体和陨石的日期表明，年龄从约4.2至39亿年不等，对年龄频谱的年轻末端有占优势。影响的证据尚未在地球动态表面幸存下来。取而代之的是，我们依靠返回任务的样本和陨石。这种天文材料形成的精确时间顺序可以回答有关地球起点的基本问题。轰炸是由于内部太阳系中的行星形成而始于整个Hadean的轰炸吗？还是普遍认为它仅限于晚期，强烈的末端灾难？地球随后的陨石影响历史记录在世界范围内约190个已知影响结构，但这些事件的精确年龄信息严重缺乏。这使得很难评估他们对地球进化过去的影响。 拟议的研究将使用铀铅（U-PB）日期与创新的提取技术相结合，研究地球的陨石影响历史，以在其地质环境中分离矿物质。首次使用高精度U-PB地球体学上的最新进展来确定月球和火星陨石以及小行星的原位年龄，以建立精确的年龄，以帮助阐明我们早期轰炸历史的时间范围。这是理解地球和其他行星如何发展的基础，以及影响磁通量如何随着时间而变化。它对理解生命的出现具有影响，这可能受到早期强烈轰炸的负面影响。 在陆地记录中，在地质和生物记录中，陨石的影响留下了其影响的痕迹。在撞击过程中，可以确定在结晶或同位素重置的矿物上确定围墙的时间。年龄对于评估对生态圈的影响和建立通量率很重要，这可能对人类人群产生影响。众所周知，至少有一种陨石撞击在白垩纪结束时在重大质量灭绝中发挥了作用。撞击的样本（例如，布伦特，卡斯韦尔，维德福，切萨皮克湾和萨德伯里）已掌握，并将针对其时间安排，目标岩石的年龄以及后影响后的热透明效果进行研究。 拟议的研究是一种新的方法，将把加拿大在世界上定位为独特。高精度的原位约会将基于我的影响约会的历史。结果将推进行星演化的领域，并通过地层记录中的相关性来评估过去对影响的环境反应。这是一项独特的加拿大努力，用于将现代U-PB约会和纳米木矿物质调查与唯一可用于微型矿物质的工具结合在一起。