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

Abstract

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

Magmatic and tectonic history of Jurassic ophiolites and associated granitoids from the South Apuseni Mountains (Romania)

“…9). Zachariadis (2007), and that of the Gerakini diorite, interpreted to belong to ophiolites although enclosed within the Chortiatis island-arc suite, is from Bonev et al (2015). A maximum age of obduction (~153 Ma) of the South Apuseni ophiolitic unit can be inferred from the youngest calc-alkaline intrusive body (sample DG072).…”

“…The very small age difference observed in the case of rocks from the Demir Kapija and Guevgueli ophiolites argues for granitoid formation in an island arc setting. Božović et al (2013) and Bonev et al (2015).…”

“…10a). The back-arc spreading apparently started earlier in the southern parts of the East Vardar marginal basin, at ~170 Ma, and was restricted to the Middle Jurassic (Koglin et al 2007;Zachariadis 2007;Božović et al 2013;Bonev et al 2015), whereas the oceanic lithosphere preserved in the South Apuseni ophiolitic unit is younger and Late Jurassic (Fig. 9).…”

“…4). The mean UPb ages of rocks from the ophiolites range from 172.8 ± 1.2 to 158.4 ± 1.9 Ma (Koglin et al 2007;Zachariadis 2007;Koglin et al 2009;Božović et al 2013;Bonev et al 2015). The granitoids and their volcanic equivalents yielded mean U-Pb ages between 164.0 ± 2 and 158 ± 1 Ma (Anders et al 2005;Zachariadis 2007;Meinhold et al 2009), and an Ar-Ar feldspar age of 164 ± 0.5 Ma (Božović et al 2013).…”

Zircon U‐Pb Chronostratigraphy and Provenance of the Cycladic Blueschist Unit and the Nature of the Contact With the Cycladic Basement on Sikinos and Ios Islands, Greece

“…Jurassic and Cretaceous DZ age modes are likely derived from arc‐related plutonic and volcanic rocks associated with Neo‐Tethys subduction (Brun & Sokoutis, ; Ricou et al, ). These arc‐related rocks can be found in the Internal Hellenides, the Rhodope, the Vardar Suture Zone, and the Pelagonian Zone (e.g., Anders, ; Bonev et al, ; Pe‐Piper & Piper, ). In the Middle Jurassic, arc‐related volcanic products were derived from the Paikon subduction zone (e.g., Michard et al, ; Zachariadis, ).…”