U-Pb zircon geochronology of metasedimentary and meta-igneous rocks of the Palatinate and Northern Vosges

The (meta-)sedimentary succession of the Northern Vosges and adjacent scarce outcrops of crystalline basement in the Palatinate Forest are located in a key position at the transition between the Mid-German Crystalline Zone (MGCZ) and the Saxo-Thuringian Zone of the Central European Variscides.

Their geotectonic positions have been discussed widely in the past; while the crystalline rocks of the Palatinate are typically assigned to the MGCZ, the Northern Vosges are considered to be part of the Saxo-Thuringian Zone sensu strictu. Detrital zircon grains reveal different age spectra, showing a wide range of source areas and supply routes from source to sink. Maximum depositional ages in the Northern Vosges range from the Neoproterozoic to Cambrian (ca. 580 - 550 Ma) in the Villé unit (Southern succession) to Upper Devonian/Lower Carboniferous (ca. 360 Ma) in the Bruche unit (Northern succession) and the adjacent Palatinate Forest. The maximum depositional ages of the detrital zircon populations are in general agreement with biostratigraphic subdivisions of the respective units.

The zircon spectra of the Villé unit are very similar to those derived from the Saxo-Thuringian Zone, indicating sediment supply from the North Gondwana margin, whereas the spectra derived from the Bruche unit and the Palatinate Forest point to a close affinity to the MGCZ. This is additionally supported by a U-Pb concordia age of ca. 370 Ma estimated for the Albersweiler Gneiss, during this and previous studies. Our new results have consequences for the interpretation of the evolution and plate tectonic reconstruction of the Central European Variscides.