Constraining genesis and geotectonic setting of metavolcanic complexes: a multidisciplinary study of the Devonian Vrbno Group (Hrubý Jeseník Mts., Czech Republic)

• Published in: International journal of earth sciences : Geologische Rundschau Vol. 103; no. 2; pp. 455 - 483
• Main Authors: Janoušek, Vojtěch, Aichler, Jaroslav, Hanžl, Pavel, Gerdes, Axel, Erban, Vojtěch, Žáček, Vladimír, Pecina, Vratislav, Pudilová, Marta, Hrdličková, Kristýna, Mixa, Petr, Žáčková, Eliška
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.03.2014; Springer Nature B.V
• Subjects: Earth and Environmental Science; Earth Sciences; Geochemistry; Geology; Geophysics; Geophysics/Geodesy; Isotopes; Magma; Mineral Resources; Original Paper; Petrology; Plate tectonics; Sedimentology; Structural Geology; Czech Rep; Geochemistry; Devonian volcanic rocks; Variscan orogeny; Bohemian Massif; Sr–Nd–O isotopes; U–Pb zircon dating
• ISSN: 1437-3254; 1437-3262
• DOI: 10.1007/s00531-013-0975-4

The low-grade metavolcanic/volcanosedimentary complex of the Devonian Vrbno Group (Silesicum, NE Bohemian Massif, Czech Republic) occurs in two ~NE–SW trending belts, separated by tectonic slices of Cadomian metagranitic paraautochton. (1) The basic–intermediate lavas of the calc-alkaline Western Volcanic Belt came from a moderately depleted mantle ε Nd 370 ∼ + 3 . Rare rhyolites (374.0 ± 1.7 Ma: 2σ, LA–ICP–MS U–Pb Zrn) were derived most likely from immature crust or by extensive fractionation of primary basaltic melts. The rock association is interpreted as a vestige of a deeply dissected continental arc. (2) The Eastern Volcanic Belt consists mainly of (nearly) contemporaneous (371.0 ± 1.4 Ma) felsic alkaline lavas with high HFSE contents, as well as high Ga/Al and Fe/Mg ratios, typical of within-plate igneous setting. The petrology and Nd–Sr isotopic data point to a high-T anatexis of a young metagranitic crust, resembling the Cadomian (Brunovistulian) basement, in a back-arc setting. The attenuated Brunovistulian lithosphere could have partially melted by the heat provided by the upwelling asthenosphere and/or underplating basic magma. (3) Finally, the region was penetrated by numerous subalkaline, MORB/EMORB-like dolerite sheets—a hallmark of the considerable crustal thinning.