Neopaleozoic and Mesozoic granitoid magmatism and tectonic evolution of the western West Kunlun Mountains

Abstract: On the basis of rock types, ages and geochemical data of Neopaleozoic and Mesozoic granites, the authors studied the magmatic stages and petrogenesis of these granites, and discussed tectonic magmatic evolution and collision orogenic process of the western West Kunlun Mountains in combination with the regional geological information. The authors have reached the conclusion that the tectonic magmatic evolution of Neopaleozoic and Mesozoic period should be divided into seven stages: (1) 388-324 Ma (northward subduction of Branch I of Tethys Ocean): granites at this stage had TTG rock association with rich sodium and poor potassium, probably formed in an epicontinental arc; (2) 339-291 Ma (Oytag back-arc basin): this back-arc basin was formed by northward subduction of Branch I of Tethys Ocean in the south, and subsequent tholeiitic ocean granites might be characterized by rich sodium and poor potassium; (3) 258-241 Ma (the stage of the closure of Branch I of Tethys Ocean and collision orogeny): the granites of this stage were gneissic S-stye granites with muscovite and garnet which should have originated from continental crust; (4) 234-210 Ma (the post collision extensional stage during TethysⅠ): huge granitic batholiths were I-A style granites which were closely associated with mantle magma underplating and magma mixing; (5) 198-150 Ma (southward subduction of Branch II of Tethys Ocean): granites of this stage had TTG rock association and were formed in continental marginal arc or island arc setting; (6) 148-118 Ma (the stage of closure of Branch II of Tethys Ocean and collision orogeny): monzonitic granites with weak gneissic structure belonged to C style adakites as a result of melting of thickening crust during continental collision; (7) 111-75 Ma (the post collision extensional stage during Tethys Ⅱ): the massive granites belonged to shoshonitic series formed by partial melting of ancient crust. The authors put forward a tectonic evolution model for the western West Kunlun Mountains during Neopaleozoic and Mesozoic based on tectonic magmatic evolution of different stages.