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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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We focused on the Pirin–Pangeon–Thasos carbonate sequence of the Rhodope thrust system, combining Sr isotopes from marble with U–Pb dating of detrital zircons from interlayered schists with outcrop near the villages of Ilindentsi and Petrovo in Bulgaria. The youngest zircon age at Ilindentsi is 266 Ma, i.e. Middle Permian, while the youngest zircon at Petrovo yielded an age of 290 Ma, i.e. Early Permian. Strontium isotopes range from 0.707420 to 0.707653, and are consistent with a Middle Permian maximum depositional age. Middle Permian sedimentation of this carbonate platform most likely occurred along the Eurasian margin rather than the Gondwana margin.

<p>In the Aegean sector of the Alpine orogen of the Eastern Mediterranean, the Sakar-Strandzha Zone (SSZ) represents a major tectonic unit that straddles the territories of Bulgaria and Turkey. The westernmost part of the SSZ in Bulgaria includes the area along the Maritsa river valley and the St. Iliya Heights, both connected through several small outcrop areas under the Cenozoic sedimentary cover. In Bulgaria, the Triassic felsic magmatism along the Maritsa river valley was inferred by Chatalov (1961) on the basis of the stratigraphy, but only a single U-Pb zircon age revealed Early Triassic (ca. 249 Ma) felsic magmatism in the SSZ of Turkey (Aysal et al., 2018). Here, we constrain the timing of Triassic magmatism using U-Pb LA-ICP-MS zircon geochronology of felsic magmatic bodies in the western part of the SSZ in Bulgaria.</p><p>A sample from a (meta) rhyolite body yielded a concordant age of 237.8 ± 3.4 Ma, which confirmed a crystallization likely concomitant with the deposition of the Triassic clastic rocks in the northern Maritsa river valley. To the east along the valley, a leucocratic granite body located south of the Permian Sakar batholith (ca. 295-296 Ma, Bonev et al., 2019), yielded a concordant age of 242.1 ± 1.8 Ma for the crystallization, having crosscutting relationships with the high-grade metamorphic basement. A leucocratic and K-feldspar porphyric meta-granite bodies yielded concordant ages of 243.3 ± 5.8 Ma and 240.6 ± 2.3 Ma, respectively, for the crystallization within the so-called Harmanli block to the south along the valley. At St. Iliya Heights a sample from the Prochorovo Formation (meta) rhyolite body yielded a concordant age of 245.4 ± 1.5 Ma for the crystallization, which implies an Early Triassic age of the clastic rocks with which it inter-fingers. In the area between the Maritsa river valley and the St. Iliya Heights at the village of Svetlina a leucocratic meta-granite body yielded a concordant age of 229.6 ± 2.4 Ma. The concordantly dated zircons that yielded Triassic ages of the igneous/meta-igneous protoliths all have Th/U ratios compatible with the magmatic process. The major elements of the dated samples reveal calc-alkaline to high-K-alkaline peraluminous felsic compositions similar to the adjacent Late Carboniferous-Permian igneous/meta-igneous rocks of the SSZ.</p><p>The U-Pb zircon ages reveal Early-Middle Triassic magmatic phase (ca. 245-230 Ma) in the western SSZ of Bulgaria. These age data provide a regional-scale temporal link for the Triassic magmatism extending to the easternmost extremity of the SSZ in Turkey. The Triassic continental type felsic magmatism in the western SSZ is interpreted to result from the ongoing Paleotethyan subduction under the Eurasian plate, which magmatism follows the development of a Late Carboniferous-Permian continental magmatic arc of the SSZ (Bonev et al., 2019).</p><p>References</p><p>Aysal, N., Şahin, S.Y., Güngör, Y., Peytcheva, I., Öngen, S., 2018. Journ. Asian Earth Sci., 164, 83-103.</p><p>Bonev, N., Filipov, P., Raicheva, R., Moritz, R., 2019. Int. Geol. Rev., 61, 1957-1979.</p><p>Chatalov, G., 1961. Compt. Rend. Acad. Bulg. Sci., 14, 503-506.</p><p>Acknowledgements: The study was supported by the NSF Bulgaria DN04/6 contract.</p>