CARBONIFEROUS TECTONICS OF THE VARISCAN BASEMENT COLLAGE IN EASTERN BAVARIA AND WESTERN BOHEMIA

The tectonometamorphic units in the Variscan basement of eastern Bavar ia and western Bohemia have a long and complex record of large-scale c ontinental deformation, metamorphism, and syn- and posttectonic magmat ism. Although there is a large database describing each of the above-m entioned phenomena, an integrated tectonic synthesis is hard to achiev e. In this paper we review some of the prominent effects in the Carbon iferous tectonic evolution, which is accountable for much of the defor mation, regionally extensive low-pressure/high-temperature metamorphis m, and abnormally intense partial anatexis and plutonism. Deformation was multistage and its kinematics were dominated by lateral compressio n, transpression, and strike-slip shearing. Tectonic units were mostly deformed ''en masse'', without operation of large, discrete shear zon es. An exception were the boundary zones of those units that had alrea dy cooled to sub-greenschist-facies temperatures before the onset of C arboniferous deformation. These boundaries were operated as normal or transtensive faults. The large present vertical thickness of the Zone of Erbendorf-Vohenstrauss at the KTB drill site is most probably due t o a combination of Carboniferous block tilting related to the intrusio n of the Falkenberg granite, and Cretaceous distributed reverse faulti ng and imbrication. Late-orogenic plutonism in the Bohemian massifled to the emplacement of at least 176 000 km(3) of granitoids. Melt flux through the Moldanubian unit may have been as high as 0.2 km/m.y., all owing the estimated volume of granitoids to be segregated by partial a natexis of the continental crust within a time span of approximately 8 .8 million years.