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 4~ ages of single grains and mineral concentrates. Late Famennian (359 Ma) mica ages from the high-grade G6ry 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~e Complex.Mid-Late Devonian high pressure events in the Krkonoge-Jizera Terrane and Orlica-Snieznik Dome are followed by coeval high temperature events between 345 and 335 Ma (Vis6an). 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-Snieznik Dome, Krkono~e-Jizera Terrane. including the Intra-Sudetic Fault. and also the eastern Lusatian Granitoid Complex. They were accompanied by contemporaneous emplacement of the Krkonoge-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. Downloaded from T h e K r k o n o g e -J i z e r a T e r r a n e

The Mazury complex of northeastern Poland forms a 200 km long, E Á/W trending anorthosite Á/mangerite Á/ charnockite Á/granite belt derived from bimodal, multiphase anorogenic magmatism and is similar to the classic anorogenic complexes of the Fennoscandian Shield (e.g. Wiborg, Salmi and Ragunda).

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A Late Tournaisian synmetamorphic folding and thrusting event in the eastern Variscan foreland: 40 Ar/ 39 Ar evidence from the phyllites of the Wolsztyn-Leszno High, western Poland Abstract A Variscan foreland in western Poland comprises two NW-trending basement highs, which are concealed under Carboniferous through Triassic strata of the Fore-Sudetic Monocline (FSM). Both highs consist of multiply deformed quartz-sericite € albite € chlorite phyllites of unknown protolith age. 40 Ar/ 39 Ar laser probe dating of white micas in up to 0.5-mm-thick mica layers, which form the S 2 axial-plane foliation in phyllites of the Wolsztyn-Leszno High, yielded an age of 340.1€2.6 Ma for the lower greenschists facies metamorphism and probably also for the F 2 folding. This deformation was associated and followed by thrusting, which brought about the basement highs. The latter delivered clasts to overlying late VisØan-early Namurian flysch basin that was mainly sourced from the Saxothuringian Sudetes in which most of the deformation occurred between 345-335 Ma. The FSM basement may represent an independent terrane, referred to as the Wielkopolska terrane, belonging to the Armorican Terrane Assemblage.