Timing of igneous accretion, composition, and temporal relation of the Kassandra–Sithonia rift-spreading center within the eastern Vardar suture zone, Northern Greece: insights into Jurassic arc/back-arc systems evolution at the Eurasian plate margin

In the Hellenides of northern Greece, the Kassandra-Sithonia and Central Chalkidiki ophiolites constitute the eastern Vardar suture zone against the Serbo-Macedonian margin of Eurasia. The mafic-intermediate to acid members in the crustal section of the Kassandra-Sithonia ophiolites have N-and E-MORB signatures compatible with an origin in back-arc spreading center. The MORB mantle source has received subduction zone input from nearby Paikon arc system as revealed by LILE and LREE enrichment. A diorite from the Gerakini complex assumed belonging to the Central Chalkidiki ophiolites shows more enriched HFSE and REE pattern relative to MORB and Na-rich character compared to the Kassandra-Sithonia ophiolites. The Sithonia ophiolite crystallization span 159-149 Ma and the Gerakini complex diorite crystallized at 173 Ma as derived from new U-Pb zircon geochronology. Main cluster of Permo-Carboniferous, a small cluster of Neoproterozoic-Cambrian and few Proterozoic, Ordovician, Triassic and Middle Jurassic inherited zircons have provenance from the Serbo-Macedonian margin units. Thus, a Late Jurassic ca.10 Ma lasting igneous accretion of the Kassandra-Sithonia back-arc crust within the eastern Vardar zone is now well-constrained, and corroborated by redefined in age Berriasian-early Valanginian supra-ophiolite cover limestones. Instead affinity to the Central Chalkidiki ophiolites, the Gerakini diorite exhibits chemical similarity to the Chortiatis arc magmatic suite of the Circum-Rhodope belt within the eastern Vardar zone, predates the Sithonia ophiolite in which supplied Middle Jurassic inherited zircons. The Chortiatis arc compared with arc-related Evros ophiolites of the Circum-Rhodope belt in Thrace region shows same 173-160 Ma life span and tectonic setting, implying across north Aegean Sea extension of the arc systems. Based on these new temporal constraints a tectonic scenario of Jurassic subduction settings and arc/back-arc systems development in the Maliac/Meliata-Vardar oceanic basins is proposed that also accounts for continental magmatism in the Serbo-Macedonian margin of Eurasia