We present field, chemical and U–Pb age data for metamafic–ultramafic bodies of the Triassic rift-related Therma–Volvi–Gomati (TVG) complex of the Serbo-Macedonian Massif (SMM) in the northern Aegean region. The TVG rocks record igneous textures overprinted by Alpine metamorphism and deformation. The high-Ti Volvi body was transformed into amphibolites, which also rim the low-Ti Gomati and Nea Roda bodies. The compositions are compatible with normal (N-) and enriched (E-) mid-ocean ridge basalt (MORB) and weak ocean island basalt (OIB) signatures of the high-Ti rocks, whereas the low-Ti rocks are depleted with respect to MORB, suggesting melt extraction from a mantle source. U–Pb geochronology reveals Triassic crystallization of the Volvi body at 240 Ma. Ordovician to Carboniferous xenocrystic zircons were found in the Stratoni body of the TVG complex, which were sampled from the SMM basement. The Triassic Arnea rift-related metagranite intrudes the Volvi body. Comparison of the compositions of the Volvi body and the Arnea metagranite of the SMM with Triassic metagranite of the Rhodope Massif (RM) supports the presence of a regional bimodal rift suite. The location of the TVG complex at the SMM–RM margin of Eurasia confirms its origin as a Middle Triassic rift suite, and its nature as a continental margin ophiolite representing an ocean–continent transition of the propagating Neotethys.
Supplementary material:
Whole-rock chemical analyses and U–Pb geochronology analytical results data tables are available at
https://doi.org/10.6084/m9.figshare.c.4087022
Thematic collection:
This article is part of the ‘Tethyan ophiolites and Tethyan seaways collection' available at:
https://www.lyellcollection.org/cc/tethyan-ophiolites-and-tethyan-seaways
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
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