Zircon U-Pb-Hf isotope systematics and whole rock geochemistry of basement rocks of the Bergsträsser Odenwald

Applicants: Prof. Dr. Matthias Hinderer

Funding: DFG

Persons of Charge: Henri Paul Meinaß

Duration: 2023 – 2024

Summary

The Mid-German Crystalline Zone (MGCZ) plays a key role for unravelling the complex pre- to syn-Variscan tectono-magmatic evolution in central Europe from the Neoproterozoic to the late Carboniferous. The most complete record of this evolution is preserved in basement rocks of the Bergsträsser Odenwald, even though highly ambivalent. While a large number of (isotope)geochemical-geochronological data and models exist for the Variscan evolution of the Bergsträsser Odenwald (between 360 and 320 Ma), information about pre-Variscan events are scarce, although new zircon ages constrain pieces of Cadomian basement and Silurian intrusiva. This new data are limited to a few samples and localities within NE-SW trending schist zones (so called “Schieferzüge”), forming the metamorphosed country rocks to the predominant Variscan granitoids (gabbros to granites). In this proposal we will close this gap of knowledge by performing a systematic geochronological-(isotope)geochemical study on metasedimentary and meta-igneous rocks from all schist belts of the Bergsträsser Odenwald. The overarching aim is to provide answers on the following open questions, which represent the three main topics of the study:

• 1. What can the Bergsträsser Odenwald tell us about the role of the MGCZ during the pre-Variscan evolution of Central Europe?
• 2. What is the geochemical and U-Pb-Hf isotope record of metasedimentary rocks of the Bergsträsser Odenwald and what can be learned about their depositional age and provenance?
• 3. How is the record of meta-igneous rocks of the Bergsträsser Odenwald linked to metasedimentary rocks in age and composition?

To place new constraints, we will carry out systematic investigations on representative detrital zircon populations (n>150 grains) from at least 10 metasedimentary rocks from all schist zones of the Bergsträsser Odenwald; combining zircon morphological studies, BSE/CL imaging of internal structures, in-situ U-Pb dating and Hf isotope analyses. A corresponding procedure is planned for 10 meta-igneous rocks. In addition, bulk-rock geochemical data (major and trace elements) will be obtained from metasedimentary rocks, and meta-igneous rocks to place tight constraints on their geotectonic setting by the time of sediment deposition and/or emplacement.