|Abstract:With the decomposition of the Langjiexue Group in recent years, it has been found that the previous studies on the Langjiexue Group, Nieru Group, Xiukang Group and Luolin Group are confused.The study of Langjiexue Group should be reconsidered.Moreover, it is controversial whether the above strata were formed in the same tectonic environments.In this paper, we study the heavy mineral characteristics, geochemical characteristics and paleontological fossils of the Langjiexue Group in Jiedexiu Town-Langjiexue country, Gongga County, China.The chemical compositions of major and trace elements in the Langjiexue Group are lower than the Clarke value of the crust. The average content of SiO2 is 74.14%, and the average value of K2O/Na2O is 0.70. The above characteristics indicates that the maturity of sandstone is low, and it has not undergone obvious epigenetic reworking.The chemical alteration index (CIA) is relatively concentrated, averaging 71.55, which belongs to low-medium weathering degree, indicating that the climate and tectonic environment are in a relatively stable state.The average values of 100Mg/Al2O3 and CaO/Fe+CaO are 7.85 and 0.314 respectively, which indicates that the Langjiexue Group formed in the deep-water anaerobic environment with moderate salinity and gradually deepened from north to south.Heavy minerals are mainly zircon, followed by rutile, with poor separation and grinding circle. ATi index is 93.3-98.97, ZTR index is 48.01-85.75, reflecting that volcanic rocks in the source area of the Langjiexue Group are abundant, and their transportation distance is relatively close.REE-La/Yb diagrams, Hf-La/Th diagrams, F1-F2 diagrams, Th/Sc-Zr/Sc diagrams and heavy mineral characteristics all show that the source area of Longjiexue Group is intermediate-acid igneous rocks and continental margin clastic rocks. Based on the evidence of paleocurrent direction, the evolution of the Zhikong-Songdo Tethys Ocean, the Middle-Late Triassic magmatic rocks in South Gangdise and the peak age (240 Ma) of clastic zircons of the Langjiexue Group, the provenance of the Langjiexue Group is South Gangdise.Tectonic discriminant diagrams show that the Langjiexue Group is a product of the specific tectonic background between the continental island arc and the active continental margin environment, and the formation environment is closer to the active continental margin side.Paleontological fossils, represented by Halobia convexa, indicate that the Langjiexue Group was formed during the Carnian-Norian period of the Late Triassic.Based on the analysis of weathering degree, provenance area, tectonic background and formation age, the formation of the Langjiexue Group coincides with the evolution of the Yarlung Zangbo Tethys Ocean.