Current understanding of the Sava Zone of the Balkans: a magmatic perspective

Abstract

The Sava Zone (SZ) forms a key tectonic boundary between Europe derived and Adria‐derived continental units in the central Balkans and hosts a discontinuous belt of Late Cretaceous volcanic and plutonic rocks whose geo dynamic significance remains strongly debated. Traditional interpretations viewed this belt as the youngest remnant of the Neotethyan Ocean, implying an oceanic environment and ophiolitic affinities. However, recent studies challenge this interpretation suggesting that much of the SZ magmatism has intracontinental origins. This revised perspective indicates that these magmatic rocks may not be associated with oceanic subduction, as previously thought, but rather with the tectono‐magmatic evolution of the European (Tisza‐Dacia) and Adria plates.

In this review we synthesize available petrological, geochemical, and geo chronological data from all major localities where Upper Cretaceous magmatic rocks occur along the broader area of Sava Zone. Magmatic activity, con strained to ca. 87–76 Ma, spans tholeiitic to alkaline basalts and composition ally diverse felsic rocks. Two contrasting magmatic domains are evident. Adria‐side localities host tholeiitic to transitional basalts with N‐ to E‐MORB like signatures derived from a relatively depleted spinel‐bearing mantle. Euro pean‐side occurrences contain enriched within‐plate basalts and lamprophyres approaching OIB‐like characteristics, requiring melting of a metasomatized lithospheric mantle extending into the garnet–spinel transition field. In our view, this asymmetry reflects lateral mantle heterogeneity rather than funda mentally different tectonic environments. The acidic rocks occurring within the European‐affinity blocks display considerably greater diversity, including A1, A2, and S‐type granitoid compositions, whereas the acidic rocks in the Dinarides (Adriatic plate) are predominantly restricted to the A2 subtype. Regionally, Sava Zone magmatism was coeval with ‐ but genetically distinct from ‐ the Apuseni–Banat‐Timok‐Sredna Gora magmatic and metallogenic belt. Whereas the latter may have formed with or without invoking an actively sub ducting oceanic domain (e.g., the proposed “Sava Ocean”), the Sava Zone mag mas in our view reflect lithospheric thinning, transtension, and mantle upwelling driven by slab rollback. These findings indicate that the Sava Zone records the transition from subduction‐driven to post‐collisional tectonics during the final reorganization of the Neotethyan margin. We therefore propose redefining this system as part of the Central Balkan Late Cretaceous Magmatic Province ‐ an intracontinental belt marking the waning stages of Tethyan closure.