Post-collosional plutonism in the south-western Bohemian Massif

The proposed geological project will examine the late-orogenic evolution of the south-western sector of the Variscan Bohemian Massif, termed the Bavarian Zone. This region is mainly occupied by 330 to 300 Ma granites and associated anatectic rocks. With its strong late Variscan heat flow, the Bavarian Zone is clearly distinct from most other parts of the Bohemian Massif. The latter are characterized by 380 to 335 Ma old subduction-collision tectonics and collisional metamorphism followed by fast exhumation and cooling from 345 to 335 Ma onward. This project focuses on deciphering the geotectonic causes and heat sources responsible for the strong, late Variscan heat flow in the Bavarian Zone. Apart from the regional geological aspects, the research will lead to a better understanding of the mass and heat redistribution and the thermal regimes during the wanning stages of collisional orogenies. The results will also provide new insight into the petrogenesis and chemical evolution of magmas in response to the decay of thickened orogenic lithosphere.

This geological research project has investigated the temperature evolution in the inner parts of the Variscan orogen during the late Carboniferous time period, using rocks from the Southern Bohemian Massif (Sumava, Mühlviertel). The investigation was carried out in the Czech and the Austria part of the Bohemian Massif, by a mixed Czech-Austrian research team. Evidence was found that the heat flow from lower into higher orogen levels was particularly strong at that time. The temperature increase resulted in extensive melting of rocks in the middle crust, and produced large amounts of granite. Applying special mineralogical investigation techniques (U-Pb age dating and geothermometry on zircon crystals), significant new insight could be obtained into the geological processes of that time period.