Study of Mass Independent Isotopic Compositions of Ru and Mo in Early Earth Rocks

早期地球岩石中钌和钼的质量独立同位素组成研究

• 批准号: 2020029
• 负责人: Richard Walker
• 金额: $ 31.74万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-12-01 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2020029&HistoricalAwards=false
• 关键词: Study; Mass; Independent; Isotopic; Compositions

The isotopic compositions of ruthenium and molybdenum in ancient rocks will be measured. So-called mass-independent variations in the isotopic compositions of these elements can reveal the cosmochemical “genetics” of planets; i.e., what they were made from. In the case of Earth, some evidence suggests the genetic signatures of these elements may have changed with time as the planet accreted, indicating that the sources of Earth’s building blocks also changed with time. The objective of this study is to ascertain the level of isotopic heterogeneity present in rocks more than 2.5 billion years old. The isotopic differences in these elements in early-Earth rocks, compared to modern rocks, will provide new insights with regard to the late stage accretionary history of Earth, as well as possible sources of water and organic molecules that were the necessary ingredients for the origin of life. This project will support a postdoctoral associate to conduct state-of-the-art research and will also involve contributions from an undergraduate as part of a senior thesis project.High-precision isotopic analysis of ruthenium and molybdenum extracted from Archean rocks will be conducted. The specific objective will be to identify and interpret genetic (nucleosynthetic) characteristics of early Earth rocks, particularly with respect to characterizing the building blocks and accretionary sequence of planet Earth. Using proven techniques including nickel-sulphide fire assay pre-concentration, chemical purification and thermal ionization mass spectrometry, Archean rocks from southwestern Greenland, as well as Eoarchean rocks from Nuvvuagittuq (Quebec), and Saglek (Labrador) will be analyzed. Most of these rocks are characterized by positive 182W anomalies, indicative of derivation from primordial mantle domains. Further, we will analyze rocks from three suites of Archean komatiites, also characterized by 182W. The results of this project will provide important information about the accretionary history of Earth. Consequently, it will advance our understanding of the events leading to the creation of a habitable planet, as well as provide clues to the evolution of the mantle during the first 2 billion years of Earth history. Findings will guide dynamical modelers of both the early Solar System evolution and the early mantle. This project will support a postdoctoral associate to conduct state-of-the-art research and will also involve contributions from an undergraduate as part of a senior thesis project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

测定古岩石中钌和钼的同位素组成。这些元素的同位素组成中所谓的与质量无关的变化可以揭示行星的宇宙化学“遗传学”；也就是说，它们是由什么制成的。以地球为例，一些证据表明，这些元素的遗传特征可能随着行星的增加而改变，这表明地球的组成部分的来源也随着时间的推移而改变。这项研究的目的是确定超过25亿年的岩石中存在的同位素不均匀性水平。与现代岩石相比，早期地球岩石中这些元素的同位素差异将为地球晚期的增生史提供新的见解，以及作为生命起源必要成分的水和有机分子的可能来源。该项目将支持博士后进行最先进的研究，也将涉及本科生的贡献作为高级论文项目的一部分。对太古宙岩石中提取的钌和钼进行了高精度同位素分析。具体目标将是确定和解释早期地球岩石的遗传（核合成）特征，特别是关于地球构造块和增生序列的特征。使用成熟的技术，包括硫化镍火测定预浓缩，化学纯化和热电离质谱，来自格陵兰岛西南部的太古代岩石，以及来自Nuvvuagittuq（魁北克）和Saglek（拉布拉多）的太古代岩石将进行分析。这些岩石大多具有182W正异常特征，表明它们起源于原始地幔域。此外，我们还分析了太古宙三套同样具有182W特征的科马岩系的岩石。这个项目的结果将提供有关地球增生历史的重要信息。因此，它将促进我们对导致宜居行星形成的事件的理解，并为地球历史上最初20亿年的地幔演化提供线索。这些发现将指导早期太阳系演化和早期地幔的动力学建模。该项目将支持博士后进行最先进的研究，也将涉及本科生的贡献作为高级论文项目的一部分。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。