An Andean type Palaeozoic convergence in the Bohemian Massif

Abstract

The geological inventory of the Variscan Bohemian Massif can be summarized as a result of Early Devonian subduction of the Saxothuringian ocean of unknown size underneath the eastern continental plate represented by the present-day Teplá-Barrandian and Moldanubian domains. During mid-Devonian, the Saxothuringian passive margin sequences and relics of Ordovician oceanic crust have been obducted over the Saxothuringian basement in conjunction with extrusion of the Teplá-Barrandian middle crust along the socalled Teplá suture zone. This event was connected with the development of the magmatic arc further east, together with a fore-arc basin on the Teplá-Barrandian crust. The back-arc region -the future Moldanubian zone -was affected by lithospheric thinning which marginally affected also the eastern Brunia continental crust. The subduction stage was followed by a collisional event caused by the arrival of the Saxothuringian continental crust that was associated with crustal thickening and the development of the orogenic root system in the magmatic arc and back-arc region of the orogen. The thickening was associated with depression of the Moho and the flux of the Saxothuringian felsic crust into the root area. Originally subhorizontal anisotropy in the root zone was subsequently folded by crustal-scale cusp folds in front of the Brunia backstop. During the Visean, the Brunia continent indented the thickened crustal root, resulting in the root's massive shortening causing vertical extrusion of the orogenic lower crust, which changed to a horizontal viscous channel flow of extruded lower crustal material in the mid-to supra-crustal levels. Hot orogenic lower crustal rocks were extruded: (1) in a narrow channel parallel to the former Teplá suture surface; (2) in the central part of the root zone in the form of large scale antiformal structure; and (3) in form of hot fold nappe over the Brunia promontory, where it produced Barrovian metamorphism and subsequent imbrications of its upper part. The extruded deeper parts of the orogenic root reached the surface, which soon thereafter resulted in the sedimentation of lower-crustal rocks pebbles in the thick foreland Culm basin on the stable part of the Brunia continent. Finally, during the Westfalian, the foreland Culm wedge was involved into imbricated nappe stack together with basement and orogenic channel flow nappes. To cite this article: K. Schulmann et al., C. R. Geoscience 341 (2009). # 2009 Published by Elsevier Masson SAS on behalf of Académie des sciences. RésuméConvergence paléozoïque de type Andin dans le Massif de Bohême. Le Massif varisque de Bohême est le résultat de la subduction, au Dévonien supérieur, de l'océan Saxothuringien sous la plaque continentale représentée à l'est par les zones actuelles

U-Pb zircon age of the Krásné Loučky tuffite: the dating of Visean flysch in the Moravo-Silesian Paleozoic Basin (Rhenohercynian Zone, Czech Republic)

“…However, it would be dif fi cult to ex plain their pres er va tion in an en viron ment where the mean reflectance R r of vitrinite is 4.32% corre spond ing to a rank of meta-an thra cite. If sig nif i cantly youn ger sed i ments had been tec toni cally in cor po rated in the lo cal stratigraphic se quence, then this must have hap pened dur ing the lat est Car bon if er ous, around 310 Ma (Bashkirian, Early Pennsyl va nian) when the lo cal Variscan orogenic belt col lapsed (Schulmann et al, 2009). This would have been the only pos sible rea son for lo cal tec tonic de for ma tion.…”

“…It was devel oped in the fore land of the Variscan orogen and be came part of its outer zones, the so-called Rhenohercynicum and Subvariscicum (Schulmann and Gayer, 2000;Schulmann et al, 2009).…”

Geochemical variability of granite dykes and small intrusions at the margin of the Granulite Complex in southern Bohemia

“…Moldanubian Zone is formed by medium-to high-grade metamorphic rocks, interpreted as a tectonic melange of lower to middle continental crustal segments of the orogenic root (Schulmann et al 2009) and intruded by numerous plutonic rocks from early Devonian calc-alkaline arc-type intrusions to late-tectonic Carboniferous granites (e.g. Finger et al 1997;Holub 1997;Gerdes et al 2000;Janoušek et al 2000Janoušek et al , 2004bJanoušek et al and Žák et al 2014).…”

Geophysical and structural pattern of the Knížecí Stolec pluton and its host rocks in the south-western part of the Moldanubian Zone, Bohemian Massif

“…Schulmann et al 2009). This complex consists of two major units with contrasting tectonometamorphic evolution.…”

“…The regional framework of the Moldanubian Zone resulted from several Variscan geodynamic events (e.g. Vrána 1979;Žák et al 2005;Büttner 2007;Schulmann et al 2008Schulmann et al , 2009Verner et al 2008Verner et al , 2009Franěk et al 2011a, b). Crustal thickening (~350-341 Ma) was followed by rapid and polyphase exhumation of lower to mid-crustal rocks associated with large-scale migmatization and regional HT-LP metamorphic overprint at ~341-329 Ma (Kalt et al 1999(Kalt et al , 2000Schulmann et al 2005Schulmann et al , 2008Verner et al 2008;Žák et al 2011).…”