U/Pb zircon geochronology on TTG rocks from South Carpathians (Romania): Insights into the geologic history of the Getic Crystalline Basement

In situ U/Pb zircon geochronology was carried out on some minor granitoids intrusions from the western Getic domain (Buchin and Slatina-Timis intrusions) and on the swarm of trondhjemitic dikes, sills and small granodiorite bodies from the northern Getic domain - South Carpathians. According to previous petrological studies these intrusions are related to partial melting of a thickened continental crust. Most of the dated zircon crystals are composite, with xenocrystic cores surrounded by multiple overgrowths. Age results on inherited cores of the Buchin and Slatina-Timis intrusions reveal ages from Neoarchean to Late Proterozoic-Cambrian that represent inheritance from old crust. As revealed by ages from zircon overgrowths characterised by oscillatory zoning, the intrusion occurred in the Upper Cambrian-early Silurian. The outer rims of the Buchin zircons record the Variscan metamorphic peak conditions suffered by the Getic basement. The U-Pb ages on inner cores from rocks of the northern Getic domain reveal Paleoproterozoic to Neoproterozoic inheritance. Prevalent ages in zircon cores and rims are in the range 539-428 Ma and seem to date a major component forming the Caledonian crustal basement of the South Carpathians. Scarce but ubiquitous ages of 320-214 Ma on rims overlap the ⁴⁰Ar/³⁹Ar ages on mylonites from the shear zone and indicate imprints of the Late Variscan dynamic retromorphism. The magmatic intrusion occurred between 110 Ma and 105 Ma in agreement with previous Ar/Ar ages (109-108 Ma).