Alpine metamorphic evolution and cooling history of the Veporic basement in northern Hungary: new petrological and geochronological constraints

Petrological and geochronological investigations were carried out on metamo rphic rocks of the Veporic unit (Inner Western Carpathians) in northern Hun gary. K/Ar and Ar/Ar data on micas and amphibole show only Alpine ages (mos tly in the range of 87-95 Ma) in this basement unit. Thermobarometric calcu lations yield lower amphibolite facies peak conditions (ca. 550+/-300 degre esC and 9+/-1 kbar) for the Eoalpine metamorphic event. Complex evolution o f gneissic rocks is reflected by the presence of discontinuously zoned garn ets, the cores of which may represent relics of a pre-Alpine (presumably Va riscan) thermal event. Zircon fission track (FT) data in the narrow range o f 75-77.5 Ma indicate that this portion of the Veporic unit was emplaced to shallow crustal levels already during the Senonian time. The relative mino r difference between zircon FT and K/Ar or Ar/Ar ages suggests very rapid c ooling during the Late: Cretaceous, most probably related to the extensiona l unroofing of the Veporic core complex. The obtained cooling ages do not s upport previous models of Tertiary uplift and exhumation of the Veporic uni t along the Hurbanovo-Diosjeno Line.