Middle-Late Jurassic chronology and source-to-sink system of the Sikeshu section in the southern margin of the Junggar Basin, Xinjiang

Abstract

With the improvement of isotopic testing technology, high-precision dating methods such as SHRIMP or LA-ICP-MS of detrital zircon have been used to analyze and infer the formation age of sedimentary basins, the source of detrital materials, and the tectonic background of the formation and widely used. The LA-ICP-MS zircon U-Pb dating method was used to study the detrital zircon in the Middle-Late Jurassic sandstone in the Sikeshu section of the southern margin of the Junggar Basin, Xinjiang. The results show that the detrital zircon ages are mainly 270~447Ma,240~440Ma,245~432Ma, and 286~360Ma. There are also several ancient zircon ages, mainly 945~1080Ma. Combined with zircon mineralogical characteristics, CL images, Th/U ratio, sandstone petrographic characteristics, and regional chronological data, the primary provenance of the Middle-Late Jurassic sandstone is mainly from the Yilinghabilga Mountains in the North Tianshan, and Carboniferous-Permian volcanic rocks, pyroclastic rocks and Carboniferous granites exposed in the Borokonu Mountains of the Central Tianshan Mountains. By comparing the age changes between the four sampling points, the change process of the North Tianshan-Middle Tianshan source-sink system is obtained. From west to east, the upper Devonian glutamate, the Middle Devonian carbonate, and the large granite bodies of the Carboniferous series constituted the early watershed. From the middle to late period of the Toutunhe Formation to the Xishanyao Formation, from east to west, the Cambrian and Silurian carbonate rocks and the large granites and other rocks formed the late water line.