Abstract:The study carried out geochemical analysis of pillow basalts in the group of Qijiaojing, Eastern Bogda Orogenic Belt in East Tianshan. The results show that the basalt belongs to subalkaline tholeiitic basalts, with slight enrichment in LREE ((La/Yb)N=189~221) and a weak Eu anomaly (δEu=089~096), presenting the typical features of islandarc basalts which have negative anomalies of Nb, Ta and Ti. The trace elements of pillow basalts, except active elements (Cs, Rb and Ba), are similar to that of lower crust, between one time to two times contrast NMORB. (La/Nb)N=182~ 262>>1 suggests that the volcanic rocks was contaminated by the lithosphere during the uprising process of magma. Zr content (>142×10-6) and Zr/Y ratio (>4) show the characters of intraplate volcanic rocks. In multiple environment discrimination diagrams, the samples of the volcanic rocks fall into the NMORB area or the margin of IAT area or the intraplate basalt area, presenting characteristics of both NMORB and IAT. Combined with the sedimentary tectonic environment of earlyCarboniferous strata in the region, it can be concluded that the southern Xialaoba area in the Eastern Bogda Orogenic Belt should be in the extension tectonic environment (arcback extension) in the Carboniferous.