TERRANES AND TERRANE BOUNDARIES IN THE SUDETES, NORTHEAST BOHEMIAN MASSIF

In the Sudetes, seven distinct lithostratigraphic terranes exhibit a s ymmetric distribution. A central region of basinal/oceanic and ophioli tic rocks, the Central Sudetic terrane is bordered, respectively to th e northwest and southeast, by the sialic Saxothuringian and Moldanubia n terranes. These exhibit contrasting metasedimentary/metavolcanic suc cessions and tectonic-metamorphic sequences, but both are characterize d by Palaeozoic plutonism. These are in turn bordered (again respectiv ely to the northwest and southeast) by the Lusatian and Moravian terra nes, which are also sialic, but contain Cadomian granitoids and repres ent rifted and now widely separated fragments of Gondwana. Along the s outhwestern flank of the Sudetes, the Barrandian terrane, largely cove red by younger sediments, extends to the southwestern margin of the Bo hemian Massif. The Sowie Gory terrane forms a klippe of high grade gne isses tectonically emplaced on top of low-grade, sheared ophiolites of the Central Sudetic terrane. The Sowie Gory terrane exhibits a histor y of three distinct, probably multi-orogenic, regional metamorphic eve nts: an early high-pressure granulite/eclogite metamorphism followed b y medium-to low-pressure granulite, and in turn by amphibolite facies metamorphism. All the terrane boundaries are complex zones of ductile to brittle shearing, modified by later brittle movements. Some, such a s the Leszczyniec shear zone, mark lines of old, pre-Variscan rift and suture zones, reactivated and overprinted during a series of Variscan ductile to brittle events of extensional shearing with related metamo rphism and plutonism.