The Cycladic Blueschist Unit of the Hellenic subduction orogen: Protracted high-pressure metamorphism, decompression and reimbrication of a diachronous nappe stack

We discuss the assembly and tectonochronology of Cycladic Blueschist Unit (CBU) in central Aegean Sea region, Greece, as a composite, subduction-related, high-pressure (blueschist to eclogite facies) stack nappes. Our work is based on review geochronologic data from islands Tinos, Syros Sifnos. In addition, we present large set 34 new, internally consistent Rb-Sr multimineral isochron age these that can be linked distinct metamorphic stages episodes ductile deformation. The reviewed new ages provide remarkably similar results indicating their interpretation robust. find three distinct, significantly diachronous, CBU nappes were sequentially accreted between ~55 ~30 Ma, with fourth ~24-22 Ma old belt, Basal Unit, below CBU. Each nappe was exhumed soon after its imprint experienced greenschist-facies overprinting partial reworking ~10 accretion. At time structurally higher exhumed, an underlying metamorphosed at conditions. suggests considerably rather coherent units during sustained lithospheric shortening subduction channel by return flow. early Oligocene underthrusting External Hellenides south Cyclades, tectonically CBU, interpreted have reduced taper Hellenic wedge, which caused significant across Cyclades region important phase out-of-sequence thrusting emplaced non-high-pressure upper above analysis shows this event also reimbrication within along recently discovered Trans Thrust.