Late Devonian to Early Carboniferous Bimodal Volcanic Rocks of the Ještěd Range Unit (W Sudetes): Constraints on the Development of the Variscan Orogenic Wedge

0145354 - GLU-S 20013247 RIV CZ eng J - Článek v odborném periodiku
Kachlík, V. - Patočka, František
Late Devonian to Early Carboniferous Bimodal Volcanic Rocks of the Ještěd Range Unit (W Sudetes): Constraints on the Development of the Variscan Orogenic Wedge.
Geolines. Roč. 13, - (2001), s. 74-75. ISSN 1210-9606.
[Meeting of the Czech Tectonic Studies Group /6./. Donovaly - Nízké Tatry, 03.05.2001-06.05.2001]
Grant CEP: GA AV ČR IAA3111102; GA AV ČR IAA3013802
Výzkumný záměr: CEZ:AV0Z3013912
Klíčová slova: bimodal metavolcanics * Variscan orogeny * Bohemian Massif
Kód oboru RIV: DB - Geologie a mineralogie
http://geolines.gli.cas.cz/fileadmin/volumes/volume13/G13-074.pdf

Late Palaeozoic volcanism characterize the Ještěd Range Unit (JRU) forming the westernmost margin of the Krkonoše-Jizera terrane (KJT) and the lowermost part of the W- to NW-directed KJT orogenic wedge (W Sudetes). The Late Palaeozoic metavolcanics of the JRU Middle/Late Devonian to Early Carboniferous sequence are represented by metarhyolite bodies, submarine basic amygdaloidal lavas and sills ( dykes) of doleritic basalts. Regarding the geochmical features, porphyroids may be compared with within-plate felsic igneous rocks. Basaltic rocks of WPB-like composition were protolith of the JRU metabasites. The primary magmas were produced by limited melting in the upwelling astenosphere associated with extension of continental lithosphere. Prior the regional metamorphism, the porphyroids were high-silica rhyolites, and may be co-genetic with the basaltic rocks by prolonged fractionation of common mantle-derived melt. The JRU Late Palaeozoic volcanism started in the latest Middle Devonian according to the fossil record, and was rather protracted as the Tournaisian flysch is intruded by diabase dykes and sills. Timespan of the Ar-Ar ages of the Variscan metamorphic events related to the waning of subduction and subsequent exhumation and thrusting on the E and S of the KJT (365-340 Ma) extends from late Famennian to the latest Tournaisian. It is shorter than, and also set within the active period of the JRU Late Palaeozoic volcanism. Tectonic setting of the lithospheric extension related Late Palaeozoic bimodal volcanism of the JRU is essentially antagonistic, albeit contemporaneous, in relation to tectonic regime of the W-propagating orogenic wedge in the other parts of the KJT. This contrast supports an idea that juxtaposition of the KJT complexes is a result of Variscan large scale nappe stacking originated since Late Devonian to Early/Late Carboniferous boundary.
Trvalý link: http://hdl.handle.net/11104/0042962