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Alpine metamorphic evolution and cooling history of the Veporic basement in northern Hungary: new petrological and geochronological constraints |
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| Authors: | Balázs Koroknai Péter Horváth Kadosa Balogh István Dunkl |
| Institution: | Geological Research Group, Hungarian Academy of Sciences, Múzeum krt. 4/A, 1088 Budapest, Hungary, Laboratory for Geochemical Research, Hungarian Academy of Sciences, Buda?rsi út 45, 1112 Budapest, Hungary, Institute of Nuclear Research, Hungarian Academy of Sciences, Bem tér 18/c, 4026 Debrecen, Hungary, Laboratory for Geochemical Research, Hungarian Academy of Sciences, Buda?rsi út 45, 1112 Budapest, Hungary, |
| Abstract: | Petrological and geochronological investigations were carried out on metamorphic rocks of the Veporic unit (Inner Western Carpathians) in northern Hungary. K/Ar and Ar/Ar data on micas and amphibole show only Alpine ages (mostly in the range of 87-95 Ma) in this basement unit. Thermobarometric calculations yield lower amphibolite facies peak conditions (ca. 550냴 °C and 9ǃ kbar) for the Eoalpine metamorphic event. Complex evolution of gneissic rocks is reflected by the presence of discontinuously zoned garnets, the cores of which may represent relics of a pre-Alpine (presumably Variscan) thermal event. Zircon fission track (FT) data in the narrow range of 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 minor difference between zircon FT and K/Ar or Ar/Ar ages suggests very rapid cooling during the Late Cretaceous, most probably related to the extensional unroofing of the Veporic core complex. The obtained cooling ages do not support previous models of Tertiary uplift and exhumation of the Veporic unit along the Hurbanovo-Diósjeni Line. |
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