Alpine metamorphic evolution and cooling history o

Authors: Balázs Koroknai Péter Horváth Kadosa Balogh István Dunkl

Publish Date: 2001/08/01

Volume: 90, Issue: 3, Pages: 740-751

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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 550±30 °C and 9±1 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 preAlpine presumably Variscan thermal event Zircon fission track FT data in the narrow range of 75–775 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 HurbanovoDiósjenő Line

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