Zircon U-Pb geochronolgy and isotopic characterization for the pre-Mesozoic basement of the Northern Veporic unit (Central Western Carpathians, Slovakia)

Ordovician magmatism can be observed in the whole Veporic unit. New single and multi-grain zircon U–Pb dating reveal an intensive magmatic activity between 470–460 Ma and a minor magmatic phase around 440 Ma in the Northern Veporic Unit. Carboniferous ages of SHRIMP and single grain TIMS U–Pb dating in this unit document intense metamorphism and magmatism during Variscan orogeny (350–330 Ma). Previously published multi-grain U–Pb data in the same area have been interpreted to show Cambrian precursor ages. A new interpretation of this multi-grain data is suggested, revealing an Ordovician (464 ± 23) precursor age and a Carboniferous metamorphic overprint. Together with previously published data on the Southern Veporic Unit and the data presented in this study, a common Ordovician precursor age for the whole Veporic unit is recognized. The isotopic signature for the Pre-Variscan basement in the Veporic unit is distinct from published data for the Tatric unit (Gneisses: Sr/Srini,460 between 0.712 and 0.715; Ndmeas,460 between –8 and –10. Amphibolites: Sr/Srini,460 between 0.708 and 0.710: Ndini,460 between 4.5 and 5.6). Only the Kralova Hola granites with a Variscan magmatic intrusion age between 330–360 Ma reveal distinct signatures and show similarities with diorites and granites from the High Tatra Mountains with Sr/Srini,330 of 0.704 and 0.706 and Ndini,330 of –0.5 and –1.7.