Nucleosynthetic sources and the age of the solar system: U isotope variations in meteorite components

核合成来源和太阳系的年龄：陨石成分中的 U 同位素变化

• 批准号: 145777827
• 负责人: Professor Dr. Stefan Weyer, Ph.D.
• 金额: --
• 依托单位: Institut für Mineralogie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2012-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/145777827?language=en
• 关键词: Nucleosynthetic; sources; age; solar; system

We propose to investigate the U isotope composition (235U/238U) of meteorites and their components, particularly that of CAIs. Uranium has two long-lived isotopes, 238U and 235U, which were produced by r-process nucleosynthesis. Its isotope composition in meteoritc materials is generally considered to be constant, which is an essential prerequisite for U-Pb and Pb-Pb dating. However, recent studies revealed significant (‰-range) U isotope variations on low-T terrestrial materials and preliminary investigations on meteoritic material have revealed that some CAIs display even more heterogeneous U isotope compositions. Such U isotope variations produce an offset on Pb-Pb ages of CAIs on the order of several Ma, if for these samples the commonly accepted U isotope composition (238U/235U = 137.88) is used for age calculations.In this study, (1) we plan to systematically investigate the U isotope composition of various groups of CAIs, mineral separates of such CAIs, and other meteoritic materials, such as leachates of bulk chondrites. (2) We plan to combine the U isotope compositions with Pb-Pb dating on the same CAIs, applying the individually analyzed U isotope composition (instead of a constant ratio of 137.88) for age calculations. (3) The measured U isotope ratios will be used to develop constraints on the possible source(s) of U isotope heterogeneities that may result from a) inherited nucleosynthetic anomalies, b) initial 247Cm excess or depletion, or c) chemical reactions that caused U isotope fractionation (similar to those observed for oceanic sediments on Earth).

我们提议研究U -Meterites及其Londo CAIS。 t（‰ - 范围）U的同位素变化，对气象材料的预先投资和预先投资已经表明，如果这些样品对这些样品，则有些偏离了更多的异质U同位素组成。 U同位素组成（238U/235U = 137.88）用于年龄计算。这类CAI的研究率和其他陨石材料，例如散装软骨的渗滤液，我们计划将其与PB-PB在PB-PB上结合。相同的CAI，分析的U同位素组成的比率为137.88），以对年龄的计算进行约束。引起U同位素分馏）。