Detrital zircon U-Pb age of Huangyangling Formation in Dujianshan area from West Kunlun, Xinjiang: implications for tectonic evolution of Tethyan Ocean

Huangyangling Formation is developed in the northern part of the Bayankara Basin in the Dujianshan area,western Kunlun,Xinjiang,which is composed of a series of fine clastic rocks such as gray feldspar lithic sandstone,gray-white quartz sandstone and gray-black siltstone,and there are a lot of tuff and carbonate lens in the middle part,which are rich in fossils,indicating the Middle Permian age. In order to further identify the sedimentary age and material source of the Huangyangling Formation in the region,two clastic rock samples were collected from the top and bottom of the first member of the Huangyangling Formation,and the zircon U-Pb age and micronutrient content were analyzed by LA-ICP-MS. The ²⁰⁶Pb / ²³⁸U ages of detrital zircon are mainly concentrated in the five ranges of 264~276 Ma,292~317 Ma,369 ~ 373 Ma,500~503 Ma,694~702 Ma. The youngest zircon has a peak age of 266.1 ±0.89 Ma,indicating that the Huangyangling Formation began to deposit in the Middle Permian. Based on the zircon micronutrient diagram,the diagenetic types of zircons and the age data obtained,the tectonic evolution of the Tethys Ocean in the region is compared,and it is considered that the detrital zircon of 264~276 Ma originates from granitic rocks and basic volcanic rocks in the Kunlun orogenic belt during the Hercynian movement,the detrital zircon of 292~317 Ma originates from the volcanic formations in the carboniferous-permian Tuokuzidaban Formation in the Kashitashi area,the 500~503 Ma detrital zircon is derived from magmatic tectonic evolution during the formation of the Paleo-Tethys Ocean body,while the 694~702 Ma detrital zircon is derived from the Tarim Block on the northern side of the Proto-Tethys Ocean or the northern Qiangtang microblock in the ocean,the detrital zircon of 369 ~ 373 Ma is inferred to be from a small-scale volcanic activity during the early cracking of the Paleo-Tethys Ocean in the Late Devonian.