1. College of Earth Sciences, Jilin University, Changchun 130061, China;
2. College of Resources and Environmental Science, Jilin Agricultural University, Changchun 130118, China

The volcanic rocks in Manitu Formation of Suolun area are composed of andesite, trachy-andesite and dacite petrographically,but they are mainly basaltic andesite or trachy-andesite with minor rhyolite based on chemical composition. Zircon U-Pb dating results show that they formed in Early Cretaceous from 130 to 132 Ma. These volcanic rocks belong to high-K calc-alkaline series. They are high in total rare earth elements (∑REE=95.19×10^-6��198.38×10^-6), with high LREE/HREE(6.38��10.59) and negative Eu anomalies (δEu=0.68��1.01). The volcanic rocks are enriched in LILE(K, Rb, Th)and LREE, but depleted in HFSE(Nb, Ta, P, Ti). Trace elements are characterized by high Sr (>499×10^-6), low Yb (the maximum is 2.83×10^-6, <3.6×10^-6) and Y (majority <29.9×10^-6), and high ratio of Sr/Y and low ratio of Rb/Sr, indicating the characteristic of arc volcanic rocks. The volcanic rocks have positive values of ε_Hf(t) (7.3��13.7), and the initial ¹⁷⁶Hf/¹⁷⁷Hf ratios for magmatic zircons is 0.282 964, suggesting that the andesitic magma of Manitu Formation was derived from the lithosphere mantle and partial melting of newly accreted lower crust, and is affected by the subduction fluid. Volcanic rocks of Manitu Formation formed in the island arc tectonic environment caused by the subductions of the Paleo-Pacific Plate beneath the Eurasian continent.