Zircon provenance and Hf isotope constraints on the Pre-Alpine evolution of the Balkan terrains: from Peri-Gondwanan accretion to Tethyan rifting

The Balkan terrains form a complex tectonic mosaic within the Vardar Tethys mega-suture zone. Constraining their pre-Alpine paleogeographic affinities remains puzzling due to intense Alpine structural overprinting. In this contribution, we present a regional dataset comprising U-Pb geochronology and Lu-Hf isotopes of >2,000 zircons from 20 localities across Adria-affiliated (Dinarides, Pelagonides) and Europe-affiliated (Serbo-Macedonian Massif, Tisza, Carpatho-Balkanides) domains.

Ubiquitous late Neoproterozoic (750-540 Ma) zircon populations in all investigated zircon grains confirm a shared provenance along the northern active margin of Gondwana. However, Paleozoic to Mesozoic trajectories reveal a considerable lithospheric asymmetry between the two blocks.

In the Europe-affiliated northern Serbo-Macedonian Massif (Juhor Mountains), schists and peraluminous leucogranites yield overlapping Middle Ordovician (~460 Ma) core ages. Coupled with Ordovician-Silurian metamorphic rims, this records a long-lived volcano-sedimentary arc linked to the Cenerian orogeny, making the SMM the most pristine Cenerian remnant. A subsequent late Early Carboniferous (~330 Ma) tectonomagmatic signal marks Variscan collision, a signature that also dominates the Carpatho-Balkanides aswell. Importantly, Triassic magmatism is entirely absent across the Serbo-Macedonian Massif north of Bujanovac and Carpatho-Balkanides.

On the other hand, the Adria-affiliated Dinaric basement (Drina-Ivanjica and Jadar-Kopaonik units) shows a distinct evolution. In the Kopaonik block, the lower Studenička Series displays a unique spectrum dominated (>60%) by a narrow Devonian population (360-400 Ma; peak ca. 370 Ma) with highly variable εHf values, recording early Paleotethyan rifting. Furthermore, the Dinaric units record a prominent Variscan signal (320-290 Ma) and a sharp, dominant Mid-Triassic (~240 Ma) magmatic pulse with within-plate Hf signatures. This Permo-Triassic signature records advanced continental rifting preceding the Neotethyan Vardar Ocean opening, which is absent in the European margin. Finally, Pelagonian S-type magmatism yields Lower Cretaceous ages (~130-105 Ma), revealing syn-collisional melting and postcollisional rifting during final Tethyan closure.

Overall, our dataset demonstrates a fundamental lithospheric asymmetry between the margins, constraining the diachronous evolution of the Paleo- and Neotethyan Oceans.