The metamorphic basement of Romanian Carpathians: a discussion of K-Ar and 40Ar/39Ar ages

Abstract

More than 600 radiometric K-Ar ages on rocks from the metamorphic basement of the Romanian Carpathians are statistically treated and discussed. The data suggest that the most pervasive Alpine rejuvenation occurred in a belt of about 100-120 km width, within which crystalline rocks were intensely reworked, undergoing a metamorphic remobilisation of Barrovian type before Middle – Late Cretaceous. This Eo-Alpine metamorphic belt outcrops on the flanks of the Mureş Zone, i.e., in the Rodna massif to the NE, and in the Northern Apuseni to the west. Away from it, ages get progressively older and outline a broad Variscan metamorphic province. In the most external part of the South Carpathians preserved pre-Variscan ages point to the former extension of the Moesian Plate. Within the study area radiometric K-Ar ages, as well as recently reported fission-track data, do not support reheating above 300°C and corresponding regional metamorphic events during meso- and neo-Alpine times.