Early evolution of meteorite parent bodies - Hf-W and U-Pb ages of zircons, baddeleyites, and phosphates

陨石母体的早期演化——锆石、斜锆石和磷酸盐的 Hf-W 和 U-Pb 年龄

• 批准号: 145900877
• 负责人: Professor Dr. Addi Bischoff
• 金额: --
• 依托单位: Institut für Geologische Wissenschaften
• 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/145900877?language=en
• 关键词: Early; evolution; meteorite; parent; bodies

Many meteorites are complex, consisting of variable constituents and fragments (i.e., in breccias) that probably formed in different environments and/or at different times. So far, only little is known about formation conditions, and crystallization/ cooling ages of individual (accessory) minerals in meteorites and how these ages can be related to processes during the formation history of the parent bodies. Therefore, the main objective of the previous project was to investigate the formation processes of small individual zircon and phosphate grains in a textural context at high spatial resolution, and to obtain age information from these minerals, which cannot be achieved by conventional analytical methods. First Hf-W ages on individual zircon grains using in situ ion microprobe analyses in thin/thick sections on petrologically well-characterized meteorite lithologies are presented in the progress report of this renewal proposal. With the successful search and analysis of phosphate grains during the first two periods of the project it became evident that the elemental study of halogens (F, Cl, Br, I) and the analysis of isotopes of H, C and Cl in phosphates hold great potential for understanding the origin of atmo-and hydrophile elements in planetesimals and planets and will be an important aspect of the proposed project. Here, the first major objective is to constrain formation conditions and alteration/recrystallisation processes of phosphates using combined crystallographical-chemical analyses to evaluate their relevance as major hosts for the uptake of atmo- and hydrophile elements in specific sample constituents and/or fragments, and to upscale these signals to the bulk meteorite composition. This interdisciplinary approach will help scaling phosphate formation processes and the dynamic uptake processes of atmo- and hydrophile elements in phosphate minerals of various sample components on a high spatial resolution and in chronological order. The second focus is to constrain the chemical formation conditions (e.g., differentiation, partial melting, metamorphism) of individual phosphates and zircon grains in different meteorite groups using a trace-elemental (i.e., REEs) approach.

许多陨石是复杂的，由可变的成分和碎片组成（即，在角砾岩中）可能形成于不同的环境和/或不同的时间。到目前为止，对陨石中单个（辅助）矿物的形成条件和结晶/冷却年龄以及这些年龄如何与母体形成历史中的过程相关知之甚少。因此，上一个项目的主要目标是在高空间分辨率的结构背景下研究小的单个锆石和磷酸盐颗粒的形成过程，并从这些矿物中获得年龄信息，这是常规分析方法无法实现的。在本更新建议的进度报告中介绍了利用原位离子微探针对岩石学特征良好的陨石岩性的薄/厚切片进行分析，对单个锆石颗粒进行的第一次Hf-W年龄测定。在项目的前两个阶段，随着对磷酸盐颗粒的成功搜索和分析，很明显，卤素（F、Cl、Br、I）的元素研究和磷酸盐中H、C和Cl的同位素分析对于了解微行星和行星中的大气元素和惰性元素的起源具有很大的潜力，并将成为拟议项目的一个重要方面。在这里，第一个主要目标是限制形成条件和蚀变/重结晶过程的磷酸盐使用相结合的结晶化学分析，以评估其相关性作为主要主机的吸收atmo和atmile元素在特定的样品成分和/或片段，并放大这些信号的散装陨石组合物。这种跨学科的方法将有助于缩放磷酸盐的形成过程和动态吸收过程中的atmo-和atmosphile元素的磷酸盐矿物的各种样品组分上的高空间分辨率和时间顺序。第二个焦点是约束化学形成条件（例如，分化、部分熔融、变质作用）使用痕量元素（即，REEs）方法。