Paleozoic Intrusive Rocks in the Nalati Mountain Range（NMR）, Southwest Tianshan： Geodynamic Evolution Based on Petrology and Geochemical Studies

A synthesis involving the data for the Nalati mountain region（NMR） in west Tianshan with a dataset including zircon U-Pb ages, Hf isotopic composition, major and trace elements of Paleozoic intrusions are presented to improve the understanding of regional geodynamic evolution. Paleozoic intrusive rocks in the NMR could be classified into four categories based on chronological and geochemical data： 480？5 Ma, 445–410 Ma, 345–320 Ma, and 295 Ma, which correspond to（1） closure of the Terskey Ocean and the opening of the south Tianshan back-arc basin, which was followed with the opening of the south Tianshan Ocean,（2） initial subduction of the south Tianshan oceanic crust,（3） major subduction stage, and（4） collision to post-collisional stage, respectively. Following the closure of the Terskey Ocean, the south Tianshan Ocean opened at Early Silurian and subducted under Yili-central Tianshan by the end of Early Carboniferous Period. The following breakoff of the subducted slab triggered partial melting of continental crust and formed voluminous granitic rocks in the NMR.