Tectonothermal evolution of the internal Alps and Carpathians: Evidence from 40Ar/39Ar mineral and whole-rock data

40Ar/39Ar dating within the internal Eastern Alps, Western Carpathians, Southern Carpathians, and Apuseni Mountains has been carried out in order to constrain and compare (1) ages of tectonothermal overprint within basement units; (2) the extent of Alpine metamorphic overprint on Permian to Mesozoic cover sequences and (3) the sequence of Alpine tectonothermal events. Stratigraphic controls suggest that all these sections were affected by Cretaceous (''early Alpine'') orogenic events during Alpine evolution. Pre-Alpine tectonothermal events range from Early Cadomian to Late Variscan within the area considered. 40Ar/39Ar ages of detrital muscovite of Ordovician-Silurian sandstones within the Eastern Alps suggest a linkage to Cadomian sources (640-580 Ma). Comparison of geochronological data from pre-Alpine Austroalpine basement complexes within the Eastern Alps, the Western Carpathians and the Apuseni Mountains indicates that these represent units which have been affected by contrasting and/or diachronous tectonometamorphic events. As indicated by new mineral age data, their tectonothermal evolution ranges from Early (e.g., c. 420-380 Ma) to Late Variscan (330-300 Ma). By contrast, preliminary amphibole and muscovite data from various basement units within Southern Carpathians argue for uniform Late Variscan cooling after medium grade metamorphism. It appears that the Eastern Alps, Western Carpathians and Apuseni Mts. represent a composite of basement units with variables ages of accretion during early to late Paleozoic orogenic events along northern margins of Gondwana. The uniform Late Variscan cooling ages within Southern Carpathian basement units are interpreted to represent cooling within rift shoulders during ongoing extension and break-up within the future Tethys realm. This interpretation is confirmed by the presence of distinct mylonite zones within the Southern Carpathians and Eastern Alps where white mica ages suggest Early Permian tectonothermal activity with cooling and extension. Based on stratigraphic and 40Ar/39Ar mineral age control on mylonites and penetratively ductilely deformed cover and basement rocks we distinguish three major Alpine tectonic events: (1) blueschist facies metamorphism in the West Carpathian Meliata unit associated with subduction of oceanic crust during the Late Jurassic (40Ar/39Ar phengite ages: 150-160 Ma); (2) varying tectonothermal overprint during continent-continent collision during the Middle and early Late Cretaceous (''pre-Gosau'' deformation event) between c. 120 Ma and c. 86 Ma. The age of deformation decreases from hangingwall to footwall units in all investigated sections. This event apparently includes an early short-lived eclogite facies metamorphism (only in the Alps) associated with A-subduction of continental crust (with amphibole cooling ages indicating subsequent exhumation and cooling between c. 136 and 108 Ma); (3) Late Cretaceous (''intra-Gosaouian'') cooling and associated activity of detachment faulting in higher tectonic levels and contemporaneous low-temperature tectonic stacking in deeper structural levels between c. 86 Ma and 65 Ma. This feature is interpreted to represent extension in an overall contractional setting. Furthermore, there is no apparent thermal overprint within the Austroalpine nappe stack in connection with the piggy-back emplacement of the entire Cretaceous nappe complex onto the stable European foreland during Tertiary continent-continent collision.