THE SUDETES AS A PALEOZOIC OROGEN IN CENTRAL-EUROPE

Two metasedimentary complexes are exposed in the Sudetes Mountains of Poland, Germany and the Czech Republic. Succession I comprises pelites and greywackes of Neoproterozoic-Cambrian age, deformed and metamorph osed prior to intrusion by S-type porphyritic granites at 515-480 Ma. Succession II comprises a sandstone-mudstone-chert sequence and turbid ite sequence of Ordovician-early Carboniferous age accompanied by bimo dal volcanogenic rocks. Both successions were intruded by late-to post -orogenic granitoid intrusions at 340-300 Ma. The sedimentary rocks of succession II show increasing maturity until mid-late Devonian times. Inversion of the basins, commencing in late Devonian-early Carbonifer ous times, was reflected in the emplacement of turbidites and olistost romes, concurrent with the uplift of a metamorphic core complex of suc cession I rocks. The original stratigraphic order of the successions w as maintained, thus crustal imbrication was not significant. Instead, extensional faulting became important, followed by transpression on al most orthogonal fault zones, resulting in the presently observed juxta position of crustal blocks. The Palaeozoic sequences developed in main ly ensialic basins on Cadomian and older basement, parts of which beca me strongly reworked (2.6 to 0.54 Ga zircon inheritance ages) and inco rporated into the Palaeozoic structures. The orogen developed either o n the rifted margin of peri-Gondwana or on a rifted-away fragment of p re-Baltica. The Sudetic section of the Variscan Orogen is of broadly A lpine style, with significant basement involvement, but apparently wit hout evidence for long-lived subduction of wide oceans or the accretio n of numerous exotic terranes.