Quantitative structural analyses and numerical modelling of ...

654 O. LEXA ET AL.(a)(b)(c)(d)Fig. 5. Photomicrographs of characteristic mineral assemblages and textures from the Stare´ Meˇsto belt: (a) M 1 assemblage Cpx–Amp–Pl–Qtz of layered amphibolite showing equilibrated annealed texture. (b) M 1 assemblage Grt–Bt–Sil in anatectic paragneiss. (c)Variscan dynamic M 2 recrystallization of C-O metagabbro from the western belt leading to strong mineral banding of amphibole andplagioclase. (d) Variscan dynamic M 2 recrystallization of amphibole and plagioclase in C-O metagabbro from the eastern belt markedby strong cataclastic grain-size reduction.footwall metapelites, respectively, while magmaticstructures are preserved in the inner part. The geometryof S 2 fabric and kinematics of deformation are identicalwith those of the western metagabbro sheet (Fig. 3).Structures of the banded amphibolite complexThe banded amphibolite complex is affected by a hightemperaturemetamorphic event characterized by arange of melt-collecting structures. The S 1 foliation ismarked by a metamorphic compositional layering bestseen in the banded amphibolites and in the tonaliticmigmatites (Figs 3a & 4a). In the northern part of thestudy area, S 1 dips to the NNE at shallow angles(Figs 2a & 3a). To the south, the S 1 moderately dips tothe west in the migmatitic metasediments and is generallyflat-lying in the banded amphibolites (Figs 2b &3b). The S 1 compositional and metamorphic layering islocally folded into rootless isoclinal F 1 folds or isaffected by asymmetrical pinch and swell boudinagewith melt collecting in some neck-zones. In the tonaliticgneisses and more rarely in the layered amphibolitesthe planar fabric is affected by extensional shearzones filled with an amphibole-bearing tonalitic melt,or the planar fabric dissipates in coarse-grained meltpatches (Fig. 4b).The Variscan D 2 deformation in the bandedamphibolite complex is marked by folding of theoriginally flat-lying Cambro-Ordovician S 1 foliation.These open to close F 2 folds strike NE–SW with subhorizontalhinges and wavelengths ranging from a fewmetres to several tens of metres (Fig. 3). Fold hingesare locally cut by subvertical, NE–SW or NW–SEtrending, conjugated shear and fracture zones filledwith granitic melts. The internal foliation within theseshear zones bears a NE–SW trending stretching L 2lineation (Fig. 3). Similar to mylonitic metagabbros,older foliations are locally affected by late F 3 foldswith hinges sub-parallel to the L 2 lineation or bydevelopment of a late S 3 crenulation cleavage subparallelto the S 2 foliation, indicating deformationcontinuity towards lower metamorphic conditions.Ó 2005 Blackwell Publishing Ltd236