New U-Pb zircon ages from Cadomian basement of the Balkan fold-and-thrust belt of northern Bulgaria

New U-Pb zircon ages are preliminarily reported here from various high-grade units within the overall low-grade Balkan fold-and-thrust belt of northern Bulgaria. The Stakevtsi gneisses yielded Cadomian ages interpreted as magma crystallization ages ranging from 651±8 Ma to 601±3 Ma, some of the samples exhibited a significant proportion of Mesoproterozoic ages with peaks at 1.6 and 1.5 Ga. Paragneisses in the Barzyia Massif exhibit complex U-Pb zircon age patterns, with age peaks typically at 580 Ma and 540 Ma, but also Paleo- and Mesoproterozoic and younger at 430 Ma to 310 Ma. The Divchovoto gneisses yielded age spectra with a minor contribution of Archean, Paleo- and Mesoproterozoic grains and a dominant population of Cadomian ages at 610 Ma. In summary, most of the samples point to the north African provenance, however, some of the Stakevtsi gneisses indicate rather a Baltican provenance. This suggests that the pre-Variscan tectonics and juxtaposition of different terranes was complex in this segment the former Cadomian orogenic belt, but also the possible proximity of Baltica to Gondwana at the end of Neoproterozoic.