The Structural and Metamorphic Record of the Variscan Oro- genesis at the Eastern Margin of the Moldanubian Zone in the Bohemian Massif Associated with the Brunovistulian Fore-

ed volcanic activity can be interpreted either as an indication of a limited width of subducted crust (not greater than 200 km) or as an indication of detachment of the sinking slab. Interpretation of the areally distributed felsic and intermediate calc-alkaline vol-canic formations are interpreted as being initiated by back-arc extension induced by diapiric uprise of “fertile ” asthenospheric material