1. College of Earth Sciences, Jilin University, Changchun 130061, China;
2. Jinan Municipal Engineering Construction Group, Jinan 250000, China;
3. Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Natural Resources, Changchun 130061, China

 Zircon U-Pb isotope dating and whole-rock geochemical analyses were undertaken for the rhyolite, rhyolitic lithic crystal tuff and dacitic tuff from the Manketouebo Formation in the Keyihe area, in order to constrain their genesis and tectonic significance. Zircon LA-ICP-MS U-Pb data indicate that the rhyolite and rhyolitic lithic crystal tuff were formed during 137±5 Ma and 143±1 Ma，respectively. These volcanic rocks have high SiO2 (70.03%–76.46%) and K2O+Na2O (8.10%–9.52%) contents, but low CaO (0.03%–0.95%) and MgO (0.07%–0.67%) contents, which belong to the peraluminous and high-K calc-alkaline rocks. They are enriched in light rare earth elements (REEs), and exhibit fractionation of light over heavy REEs, with δEu values of 0.37–0.83. The volcanic rocks are enriched in LILEs (e.g., Rb, U and K) and depleted in HFSEs (e.g., Nb, Ti, P and Ta). The chemical composition suggests that these volcanic rocks formed by partial melting of crust material. Combined with previous regional research results, the authors consider that the volcanic rocks of the Manketouebo Formation in the Keyihe area were formed under an extensional environment related to the closure of the Mongolia–Okhotsk Ocean.