The igneous rocks in the upper Sawuershan formation in the Ur, kashgar area, West Junggar, are paralic and basic-intermediate pyroclastic rocks with volcano lava rocks. The age of andesite is 391±3Ma based on LA-ICP-MS zircon U-Pb dating of andesite. The igneous rocks enrich in LILE （K、Rb、Cs、Sr、Ba）and show negative anomalies in HFSE （Nb、Ta、Zr、Hf） reflecting typical geochemical characteristics of arc volcanic rocks, but basaltic andesite ( SiO2=52.9%~55.3% ) and andesite ( SiO2=62.01%~62.41% ) owns significantly different value of ( La/Yb ) N (3.5~8.0,21.4~23.6 respectively), suggesting that they have different source areas, basaltic andesite mainly roots in mantle wedge peridotites which is metasomatized by fluid in subduction belt, while andesite is similar to geochemical characteristics of adakitic magma, which is the product of partially rmelted subducted oceanic slab under eclogite facies conditions.