VARISCAN TECTONICS OF CENTRAL-EUROPE - POSTACCRETIONARY INTRAPLATE DEFORMATION OF WEAK CONTINENTAL LITHOSPHERE

The area occupied by the Variscan belt of central Europe forms part of Gondwana-derived microplates (essentially Avalonia and Armorica) that , according to paleomagnetic data, juxtaposed Baltica and Laurentia fr om the Upper Ordovician to the Lower Devonian. The actual structure of this area is a puzzle of rather small fault-bounded crustal blocks, d ifferent in P-T-t-histories, which was created by later tectonic proce sses, at around 360 to 320 Ma. According to a common view and by contr ast to paleomagnetic data, the structural record of fault-bounded bloc ks is interpreted in terms of Mid-Devonian to Lower Carboniferous amal gamation of narrow continental plates represented by the fault-bounded blocks themselves. However, this is not supported in this article. In stead, it will be shown that fault-systems and fault-bounded blocks we re created by intraplate deformation of a weak domain of Gondwana-deri ved continental lithosphere, significantly after its accretion. Deform ation was partitioned into newly formed deep-seated strike-slip and (k inematically connected) reverse or normal detachment systems. Large tr anslation magnitudes caused juxtaposition of crustal areas of variable thickness. Until they were emplaced along the fault systems, the vari ous categories of fault-bounded complexes record different tectonic ev ents. Category 1 metamorphic complexes represent deep-seated parts of thickened crust, some time before unroofing on the detachment systems between about 340 (360) and 320 Ma. However, the record of subduction and extreme crustal thickening during earlier stages of the collision history was erased to a high degree and is only preserved by mineral a nd structural relies. Strike-slip and detachment systems propagated ac ross and dismembered tectonic boundaries, formed during these early ev ents. Category 2 metamorphic complexes and the Barrandian Basin record ing predominant pre-late Devonian metamorphic or stratigraphic events represent the brittle upper crustal parts during continuing metamorphi sm in the category 1 complexes. Weakly or unmetamorphosed lower Paleoz oic category 3 basins represent areas of thinned continental crust and record subsidence before, and to some degree, during activity of deta chment systems. The complex overall kinematic pattern of block-boundin g strike-slip and detachment systems indicates compression and extensi on acting simultaneously. This probably reflects the effects of contin uing oblique plate convergence, rotation, and WSW-extrusion of fault b ounded blocks, in addition to heating, and extensional flow of previou sly thickened crustal areas.