U/Pb zircon dating of pre-Variscan basement, Tauern Window

Research project P 14228 U/Pb zircon dating pre-Variscan basement, Tauern Window Urs KLÖTZLI 08.05.2000 A more conclusive understanding of the pre-Variscan (pre-"Zentralgneis") evolution of the basement formations in the Tauern Window is highly desirable, as this still forms an important missing part for a meaningful palaeo- tectonic reconstruction of pre-Variscan Europe. Aim of the proposed research project is therefore to provide exact age constraints on the pre-Variscan magmatic, sedimentary, and metamorphic evolution of the central Tauern Window and thus to contribute to the knowledge of the relationship between northern Gondwana and southern Laurasia during the Upper Proterozoic and Palaeozoic. Using single zircon vapour digestion U/Pb, single zircon evaporation Pb/Pb, and zircon ion microprobe U/Th/Pb geochronology, combined with cathodoluminescence and back scattered electron imaging, the following litho- tectonic units of the central Tauern Window shall be investigated in order to answer the listed points of interest: 1) Eiser Formation - maximum sedimentation age of Eiser Formation; - age relation between Eiser Formation and Basisamphibolit / Habach Formation. 2) Zwölferzug - age relation between Zwölferzug and Basisamphibolit. 3) Basisamphibolit, Enzingerboden ultrabasite complex - internal age relations and age relation to Zwölferzug / Habach Formation; - maximum sedimentation age of paragneisses, age relation to Riffl-Decke. 4) Riffl-Decke - maximum sedimentation age of paragneisses and age relation to metasediments of Basisamphibolit; - age relation of igneous rocks to paragneisses.