The late Cretaceous accretionary complex along the İzmir-Ankara-Erzincan (IAE) suture zone, Northern Turkey, includes various types of metamorphic rocks together with radiolarite, sandstone, mudstone, serpentinite, basalt and limestone. Meta-plagiogranite blocks (up to 5 m in diameter) and a meta-gabbro (800 x 500 m) slice crosscut by meta-plagiogranite are observed in a matrix of serpentinites, mudstones, and radiolarian chert. These meta-gabbros and meta-plagiogranites exhibit subduction-related geochemical characteristics. LA-ICP-MS U-Pb dating of zircons from two meta-plagiogranites yielded 222.3 ± 1.5 and 227.2 ± 1.6 Ma crystallization ages. This study is the first to determine that the meta-gabbro and meta-plagiogranite from the accretionary complex were remnants of metamorphosed equivalents of the late Triassic lower crustal rocks of the subducted Tethyan oceanic crust. Moreover, they are the oldest lower crustal rocks observed in the IAE suture zone.

Both meta-gabbros and meta-plagiogranites have Na-Ca amphiboles pointing to blueschist metamorphism. On the other hand, phengites from a blueschist-facies rock yielded an 40Ar/39Ar age of 104.3 ± 0.7 Ma indicating that blueschist metamorphism occurred during the Albian. All these data suggest that the oceanic crust formed during Norian, and metamorphosed during Jurassic to early Cretaceous, and dismembered during late Cretaceous accretionary complex formation.

Supplementary material:https://doi.org/10.6084/m9.figshare.6509984.v2

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