Subduction-accretion complex with boninitic ophiolite slices and Triassic limestone seamounts: Ankara Mélange, central Anatolia

Abstract Ophiolitic mélanges in Anatolia represent Mesozoic subduction-accretion complexes, which are unusually poor land-derived coarse-clastic rocks. A segment of the ophiolitic mélange Beynam region south Ankara was studied. The consists three accretionary units (AUs), distinguished by lithology, structure, age and geochemistry. At base there is a serpentinite mélange, overlain semi-intact Upper Jurassic ophiolite with boninite topmost AU ocean-island-like alkali basalts seamount-derived Triassic shallow-marine limestones radiolarian cherts, stratigraphically Cretaceous fore-arc turbidites. sequence palaeontologically isotopically dated to early middle Campanian ( c . 81 Ma). Detrital zircons from indicate Late (87–81 Ma) magmatic arc as source. formation complex two-stage process. first stage took place during – Early Cretaceous, when supra-subduction type oceanic crust generated, subduction accretion intra-oceanic. In second jumped inboard, creating an Andean-type convergent margin, incorporated complex. lack sandstones can be attributed intra-oceanic limestone deposition upper plate main phase Cretaceous.