Ordovician blueschist metamorphism as a reflection of accretion-collision events in the Central Asian orogenic belt

A brief review of Ordovician blueschist complexes on the southwestern framing of the Siberian craton is presented in order to place further age constraints on the tectonic evolution of the Central Asian orogenic belt (CAOB). Three different blueschist localities (imbricated slices of blueschists in the Uimon Zone, Gorny Altai; a blueschist unit in the Kurtushiba ophiolite belt; blocks of blueschists and eclogites in a serpentinite mélange of the Chara (Char) zone, northeastern Kazakhstan) are considered. We obtained 40Ar/39Ar dates for white micas and sodic amphiboles from blueschists of the Uimon Zone (490–485 Ma), Kurtushiba belt (470–465 Ma), and Chara zone (450 Ma), suggesting the Ordovician ages of the subduction/exhumation of these complexes. The dates obtained also coincide with the metamorphic ages of many blueschist belts in North China, which allows us to distinguish the Ordovician stage of accretion-collision events in the tectonic evolution of the CAOB.