TERRANE BOUNDARIES IN THE BOHEMIAN MASSIF - RESULT OF LARGE-SCALE VARISCAN SHEARING

A new subdivision of the pre-Permian rocks of the Bohemian Massif into terranes is based on recent structural, kinematic and radiometric studies and on a comparison with the French Variscan Belt (mainly the Massif Central). Major tectonothermal events are attributed to the Variscan (390-300 Ma) and the terrane boundaries trending roughly SW-NE to SSW-NNE to Variscan thrusts or ductile strike-slip faults. On a NW-SE section from the Saxothuringian area to the Moravian Carboniferous foredeep, the Bohemian Massif appears as a fan-like divergent orogen with two high-grade metamorphic belts (the Saxothuringian with northwest vergence and the Moldanubian with an east to southeast vergence) separated by a less metamorphic and much less eroded block, the Barrandian. From southeast to northwest the belt may be divided into six terranes: Moravian, Drosendorf and Gfohl (previously grouped in the Moldanubian zone), Barrandian, Münchberg-Tepla and Saxothuringian. These terranes have all suffered different geological histories and are now separated by major thrusts of strike-slip faults. This configuration is the result of a complex Variscan history, probably including an early subduction and closure of an oceanic domain followed by obduction, continental collision, continental subduction and strike-slip faulting lasting more than 80 Ma. © 1990.