TRANSFORMATION OF A MAGMATIC ARC AND AN OROGENIC ROOT DURING OBLIQUE COLLISION AND ITS CONSEQUENCES FOR THE EVOLUTION OF THE EUROPEAN VARISCIDES (MID-GERMAN CRYSTALLINE RISE)

The architecture of the European Variscides has been subdivided by Kos smat (1927) into paleo-geographically coherent units which are present ly interpreted as former plate fragments. The Mid-German Crystalline R ise (MGCR) separates two fragments (Rhenohercynian and Saxothuringian belts) at the site of an inferred plate boundary and reequilibrated or ogenic root. The commonly favoured model interprets the MGCR as the ma gmatic are on Saxothuringian crust above a south-dipping subduction zo ne in Upper Devonian and Carboniferous times. Data from the MGCR, the kinematic evolution of the Mid-European Variscides, and first order vo lume balancing suggest a reinterpretation of this unit which challenge s classical views on the MGCR as well as on the subdivision of Varisca n architecture. The MGCR is composed of two rock groups with different tectonic identity. A Lower Carboniferous low pressure-high temperatur e magmatic are association on Lower Paleozoic basement rests tectonica lly on a stack of medium pressure-medium temperature rocks of inferred Rhenohercynian origin. The latter were tectonically accreted to the b ase of the overriding plate by tectonic underplating. The entire proce ss was controlled by oblique convergence. This led to regional partiti oning of the plate kinematic vector into contractional domains (lower Rhenohercynian plate and back-are area of the upper Saxothuringian pla te), bulk heterogeneous plate margin parallel extensional domains (MGC R), and plate margin parallel wrench domains (MGCR boundaries). During this process material was continually transferred from the lower plat e to the upper plate, uplifted and exhumed by net crustal extension. T he concomitant removal of parts of the former are and the entire oroge nic root necessitates a reappraisal of Variscan architecture and evolu tion.