Abstract:The Late Carboniferous Aladeyikesai Formation volcanic rocks consist of basalt, basaltic andesite and andesite, Halaalate Mountain, western Junggar. The U-Pb zircon LA ICP-MS age of the basalt closely associated volcanic rocks is 303.8±2.4Ma, MSWD=0.82(95% conf.). The volcanic rocks are belong to sub-alkaline series, geochemical study shows the SiO2 ranging from 51.05% to 59.30%, TiO2 ranging from 0.90% to 1.33%, total alkaline (K2O+Na2O) ranging from 3.97% to 8.07%, showing relative rich in sodium, but poor in potassium(Na2O/K2O>2), A12O3 ranging from 16.58% to 19.84%, MgO ranging from 2.50% to 5.01%, and Mg# ranging from 35.04 to 47.62.All samples are characterized by higher rare earth elements(∑REE=41.12×10-6~73.93×10-6) and LREE enrichment((La/Yb)N=2.01~5.33), but weak negative Eu anomaly (Eu/Eu*=0.72~0.88). In addition, they display LILE enrichment (such as Ba、Th、K and Sr), HFSE depletion (Zr and Hf), obvious Nb and Ta negative anomalies, and slight Ti depletion. The geochemical characteristics show that all the rocks from the Aladeyikesai Formation were product of active continental margin arc volcanism in the south of the Boshchekul-Chingiz arc with the source of depletion mantle and mainly affected by the fluid from the subduction zone. So we proposed the orogeny in the east of western Junggar was later than in the west,furthermore, provides evidence for further understanding the tectonic evolution of western Junggar.