Quantitative structural analyses and numerical modelling of ...

EXTRUSIONOFLOWERCRUSTINVARISCANOROGEN 55(a)(b)Fig. 1. (a) Principal divisions of the Variscan chain. RH, Rhenohercynian domain; SX, Saxothuringian domain; MO, Moldanubiandomain. (b) Simplified geological map of the Bohemian Massif modified after Franke (2000).Tepla´-Barrandian domain consists of primitiveNeoproterozoic siltstones to greywackes and volcanicrocks deposited on an oceanic or transitional crust(e.g. Cháb & Pelc, 1973) and weakly metamorphosedduring the Cadomian orogeny (Kettner, 1918). ThisCadomian basement is unconformably overlain byCambrian and Ordovician to mid-Devonian sedimentarysequences that consist of greywackes, shales,sandstones and limestones. The Variscan tectonometamorphicprocesses are most pronounced in thewestern part, where they are restricted to 385–360 Ma(Fig. 2; Appendix S1). The boundary to the east withthe migmatites of the Moldanubian domain is markedby intense strike-slip deformation along the so-calledCentral Bohemian Shear Zone (Rajlich, 1988; Pitraet al., 1999; Scheuvens & Zulauf, 2000), however, thetrue contact is often masked by 375–336 Ma (Fig. 2)intrusions of the Central Bohemian Plutonic Complex(e.g. Zˇa´k et al., 2005a). The boundary betweenMoldanubian migmatites and the SW part of theTepla´-Barrandian domain is marked by the so-calledWest-Bohemian Shear Zone (Zulauf et al., 2002; Do¨ rr& Zulauf, 2008).The Moldanubian domain corresponds to theinternal orogenic root zone of the Variscan orogen(Suess, 1926). It is intruded by numerous Variscanplutons ranging from I-type (e.g. specifically K–Mgrich syenites or calc-alkaline arc-related rocks, Janousˇeket al., 2000) to S-type granitoids (Finger & Steyer,1995). The Moldanubian–Brunia boundary is markedby a several-kilometres-wide zone of highly deformedme´lange derived from both the units (Konopa´seket al., 2002). The Moldanubian domain is traditionallydivided into three tectonic units (Fuchs, 1976). Thestructurally deepest medium-grade MonotonousGroup is overlain by the medium-grade Varied Groupand the structurally highest high-grade Gfo¨ hl Unit.The Monotonous Group consists of biotite-plagioclaseparagneiss with minor orthogneiss, quartzite,amphibolite and locally eclogite bodies (Medaris et al.,1995; OÕBrien & Vra´na, 1995). It contains metagranitoidsof Early Palaeozoic age (see Fig. 2), suggesting aPrecambrian age for the protolith of the surroundingparagneiss (Finger & von Quadt, 1995; Friedl et al.,2004). The Varied Group includes more pelitic protolithsand abundant amphibolite, quartzite, marble andÓ 2010 Blackwell Publishing Ltd207