In the Sudetes, seven distinct lithostratigraphic terranes exhibit
a
symmetric distribution. A
central region of basinal/oceanic and ophiolitic rocks, the
Central Sudetic terrane is bordered, respectively
to the northwest and southeast, by the sialic Saxothuringian and Moldanubian
terranes. These exhibit contrasting
metasedimentary/metavolcanic successions and tectonic-metamorphic sequences,
but both are characterized by Palaeozoic plutonism. These are in turn bordered
(again
respectively to the northwest and
southeast) by the Lusatian and Moravian terranes, which are also sialic,
but
contain Cadomian granitoids
and represent rifted and now widely separated fragments of Gondwana. Along
the southwestern flank of the
Sudetes, the Barrandian terrane, largely covered by younger sediments,
extends
to the southwestern margin
of the Bohemian Massif. The Sowie Góry terrane forms a klippe of
high
grade gneisses tectonically
emplaced on top of low-grade, sheared ophiolites of the Central Sudetic
terrane.
The Sowie Góry terrane
exhibits a history of three distinct, probably multi-orogenic, regional
metamorphic events: an early high-pressure
granulite/eclogite metamorphism followed by 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 as 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 metamorphism and plutonism.
Garnet pyroxenite in the Biskupice peridotite, Bohemian Massif: anatomy of a Variscan high-pressure cumulate