Abstract: The Upper Carboniferous volcanics of Qianxia Formation are distributed at the north side of lower carboniferous ophiolite near Bayingou,which are mainly composed of pyroclastic rocks and interbeded lava and terrestrial clastic sedimentary rocks.According to the lithology and geochemistry,the volcanics are mainly andesite suite including trachyandesite,basaltic andesite,andesite and dacite,its Rittman index σ=1.20-3.43,attached to calc-alkaline,and ΣREE=69.53×10^-6-111.32×10^-6,ΣCe/ΣY=1.12-2.25,(La/Yb)_N=1.86-5.39,Eu=0.79-1.21,these data show that LREE are concentrated and europium depletion is not obvious.Moreover lielements such as K,Rb,Ba,and Th are rich in the rocks but the high field strength element (HFSE) such as Nb,Ta,Hf,Ti,and Y are depleted,of which the Nb content is almost 1.89×10^-6-2.65×10^-6,similar to the average value of Nb in oceanic crust which is 2.2×10^-6.The initial ratio of Sr is up to 0.704 15-0.704 19,almost equal to 0.704 37 belonging to basalt in the island-arc province,these features are associated with continental island-arc volcanics near benioff zone.In addition the subt idal-bat hyal facies sedimentary and lower carboniferous ophiolite near Bayingou exist at the same period,all have been confirmed that the Qianxia Formation volcanics are products generated from lower carboniferous ophiolite near Bayingou when the oceanic crust are subducted into the continental mass northward in late carboniferous age in the convergence zone.