NEOPROTEROZOIC - EARLY PALEOZOIC GEOTECTONIC HISTORY OF A GONDWANA-DERIVED TERRANE IN CENTRAL EUROPE (TEPLÁ-BARRANDIAN, BOHEMIAN MASSIF)

The Teplá-Barrandian unit (TBU) of the Bohemian Massif represents a Gondwana-derived fragment of the Armorican Terrane Collage containing Neoproterozoic basement units and Cambro-Ordovician overstep sequences. The Neoproterozoic volcano-sedimentary successions are part of the Cadomian-Avalonian orogenic belt. Geochemistry and petrography of the sedimentary rocks display an arc signature. First U-Pb-SHRIMP data of detrital zircons from a Neoproterozoic sandstone-mudstone suite show age patterns of 560-590 Ma, 600 Ma, 870 Ma, and 2 Ga. The Neoproterozoic successions are unconformably overlain by Paleozoic sequences. In the Lower Cambrian the deposition of 2500 m non-marine sandstones and conglomerates is accompanied by synsedimentary volcanic activity in the eastern part of the TBU. In the western part Lower Cambrian plutons are exposed. The Middle Cambrian is characterized by marine siliciclastics showing a decrease in maturity and a change in provenance compared with the Lower Cambrian sediments. Sequence stratigraphic investigations show three second-order sequences during the Lower and Middle Cambrian, which were controlled by rift tectonics. REE data of the Cambrian sediments dot to a deposition in strike slip related basins. In the Upper Cambrian chiefly tholeiitic and calcalkaline volcanics with intermediate to acidic geochemistry were deposited. The rhyolites as the youngest stage of the Cambrian volcanism have an U-Pb-SHRIMP age of 499 ± 5 Ma. Upper Cambrian strata dated by key fossils are not known. We suggest a period of intense chemical weathering and erosion during Upper Cambrian times. The Ordovician consists of marine siliciclastic sediments. Synsedimentary basic volcanism (alkaline) is present. Detrital white micas from Middle Ordovician shales reveal a Neoproterozoic (600 Ma) K/Ar age of the source rocks. The Late Ordovician Sahara glaciation is documented with glaciomarine diamictites. During Devonian to Lower Carboniferous Variscan collision processes the Teplá-Barrandian was detached from its basement and is now situated within high-grade units of the Bohemian Massif.