SHRIMP zircon U-Pb dating for subduction-related granitic rocks in the northern part of east Junggar, Xinjiang

SHRIMP U-Pb zircon dating on the Xileketehalasu granodiorite porphyry and Kalasayi monodiorite porphyry that intrude middle Devonian Beitashan Formation at the north part of east Junggar region shows that they were formed at 381 ±6 Ma and 376±10 Ma respectively. They are interpreted as subduction-related granitic rocks, which is the first report that the isotopic ages for the granitic rocks range from 350 to 390 Ma. Another determined age for the Kalasayi monodiorite porphyry is 408±9 Ma, representing the age of underlain Lower Devonian volcanic rocks. Thus, the U-Pb dates suggest that the northeastward subduction of Junggar ocean from southwest occurred at 408 to 376 Ma (the real interval may be larger). Because the ore-bearing porphyry intruded following the formation of the volcanic rocks of middle Devonian Beitashan Formation, their tectonic setting is similar to the Andes Mountains that hosts world-class porphyry copper deposits, and the researched area could be regarded as a potential area for prospecting large porphyry copper deposits.