1. College of Earth Sciences, Jilin University, Changchun 130061, China;
2. Xinjiang Institute of Geological Survey, Urumqi 830000, China

The petrology, zircon LA-ICP-MS U-Pb dating, whole rock geochemistry and Sr-Nd isotope analysis of the volcanic rocks from Yamansu Formation within the southern Aqi Mountain in Jueluotage tectonic belt, eastern Tianshan, suggest that the volcanic rocks in the study area are mainly composed of andesite, decite and rhyolite as well as corresponding volcaniclastic rocks, with a small amount of basalt. Zircons from the main rocks (andesite and rhyolite) are euhedral-subhedral in sharp, displaying fine-scale oscillatory growing zoning with high Th/U ratios (0.44~1.53), indicating a magmatic origin. The geochronological results indicate that the volcanic rocks formed in the Early Carboniferous to Late Carboniferous (318.6~324.4 Ma). Geochemical data indicates that all of the volcanic rocks have the following characteristics:acidic volcanic rocks fall in the medium-potassic calc-alkaline series, andesite and basalt fall in the series of high-potassic calc-alkaline; the REE distribution patterns are right deviated with significant fractionation of light and heavy rare earth elements (LREE/HREE=2.91~9.92); the rocks are all enriched in large ion lithophile elements (Rb, Ba, K, La, Ce) and relatively depleted in high field strength elements (Nb, Ta, P, Ti); the (⁸⁷Sr/⁸⁶Sr)_i values and ��_Nd(t) values range from 0.704 01 to 0.706 36 and 4.14 to 7.21, respectively. In conclusion, all the evidence indicates that the primary magma of the mafic rocks are generated by the partial melting of the depleted mantle wedge metasomatized by subduction fluids, whereas the primary magma of the acidic volcanic rocks are generated by partial melting of the juvenile crustal material. Combined with the previous research results, it is suggested that the primary magma of the late Early Carboniferous to early Late Carboniferous volcanic rocks from the Yamansu Formation within the southern Aqi Mountain area formed in continental margin environment during the subduction of the Paleo-Asian Ocean plate beneath the middle Tianshan plate.