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

• Applicant: Professor Dr. Addi Bischoff
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2010 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 145900877

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.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1385: The first 10 Million Years of the Solar System - A Planetary Materials Approach
• International Connection: Switzerland
• Participating Person: Professor Dr. Klaus Mezger