Publication Date:
2002-01-01
Description:
The West Sudetes (NE margin of the Bohemian Massif) consist of a complex mosaic of several tectonometamorphic units juxtaposed during the Variscan orogeny. The polyphase Variscan tectonothermal development of the West Sudetes was determined by 40Ar/39Ar ages of single grains and mineral concentrates. Late Famennian (359 Ma) mica ages from the high-grade Gory Sowie Block suggest continuous uplift after a Late Devonian high temperature-low pressure (HT-LP) event contemporaneous with the end of subduction-related high pressure-low temperature (HP-LT) metamorphism in the East Krkono[s]e Complex. Mid-Late Devonian high pressure events in the Krkono[s]e-Jizera Terrane and Orlica-[S]nie[z]nik Dome are followed by coeval high temperature events between 345 and 335 Ma (Visean). The latter are interpreted as consequence of uplift, and decompression during overthrusting of both complexes on their forelands. Subsequent small- to large-scale shear movements dated at around 325-320 Ma (early Namurian) affected the Orlica-[S]nie[z]nik Dome, Krkono[s]e-Jizera Terrane, including the Intra-Sudetic Fault, and also the eastern Lusatian Granitoid Complex. They were accompanied by contemporaneous emplacement of the Krkono[s]e-Jizera pluton. The upper limit of the tectonometamorphic and magmatic activity is dated at 314-312 Ma (Namurian/Westphalian boundary). The final juxtaposition of the diversified tectonometamorphic units, which constitute the West Sudetes, took place in early Namurian times.
