Abstract: The Wufeng-Longmaxi Formation shales show great variations in sedimentological, mineralogical and geochemical characteristics across the Sichuan Basin and its surrounding areas. Provence and sources are the basis in determining  composition, mineralogy, and brittleness of shale. In this paper, we analyze the geochemical characteristics, source rock properties and tectonic setting of the Wufeng-Longmaxi shale in the Sichuan Basin and its surrounding areas based on major elements, trace elements, and rare earth elements data. The results show that the main components of the Wufeng-Longmaxi shale are SiO₂, CaO and Al₂O₃ in the Sichuan Basin and its surrounding areas. From the southwest to south -southeast -northeast Sichuan, the SiO₂ content in the Wufeng-Longmaxi Formation shale increases gradually, while the CaO content decreases gradually. The La/Yb-REE diagram shows that the source rocks of the Wufeng-Longmaxi Formation shale have certain variations in different areas of Sichuan Basin and its surrounding areas. The source rocks of the Wufeng-Longmaxi Formation shales are similar in southwest Sichuan and South Sichuan, mainly consisting of alkaline basalt, sedimentary rocks and granites. The shale source rocks of southeast Sichuan are mainly composed of granite and alkaline basalt, while the shale source rocks of northeast Sichuan are mainly composed of sedimentary rocks and granites. The ICV index analyses reveal that the source of the Wufeng-Longmaxi shales in southwest and south Sichuan is a result of rapid deposition of the first cycle of the near source, while the Wufeng-Longmaxi shales in southeast and northeast Sichuan have undergone recycling or strong chemical weathering. The analyses of Sc/Cr-La/Y diagram and other related parameters indicate that the Wufeng-Longmaxi Formation shale in the Sichuan Basin and its surrounding areas was deposited in a passive continental margin.

Key words: Shale, Wufeng-Longmaxi Formation, provenance analysis, tectonic setting, Sichuan Basin