U-Pb-Hf zircon geochronology of metasedimentary and meta-igneous basement rocks of the Odenwald Crystalline Complex– implications for pre-Variscan geodynamic evolution of Central Europe

The Mid-German Crystalline Zone (MGCZ) plays a key role to unravel 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 and geochronological data and geodynamic models exist for the Variscan evolution of the Bergsträsser Odenwald (between 360 and 320 Ma), information about pre-Variscan events is scarce, although lately published zircon ages constrain pieces of Cadomian basement and Silurian intrusiva. Our new results of zircon U-Pb dating confirm these findings, but additionally point to a widespread occurrence of pre-Variscan intrusive rocks in the Bergsträsser Odenwald, which are known so far in this extent only from the Böllstein Odenwald.

Detrital zircon grains reveal different age spectra, pointing to a wide range of source areas and supply routes of the detritus from source to sink. Some age spectra correlate well with published data from other units of the MGCZ or the Saxo-Thuringian Zone, whereas others are completely different, and unique for the Odenwald. Maximum depositional ages range from the Neoproterozoic (c. 550 Ma) to Early Variscan (c. 355 Ma) and indicate that the Odenwald basement preserves different periods of sediment deposition and a prolonged geodynamic evolution, much longer and complex than previously thought. Our new results have consequences for the interpretation of the evolution of the MGCZ and adjacent areas within the Central European Variscides.