⁴⁰Ar/³⁹Ar dating and geochemical analyses have been carried out on mafic volcanic rocks of the Qingshan Group collected from Jiaodong Peninsula. In combination with previously published data on the silicic rocks of the Qingshan Group, the newly acquired data show that: 1) the mafic volcanic rocks erupted during 122～113 Ma, predating the silicic volcanism (110～98 Ma); and 2) the mafic and silicic rocks display distinct elemental and isotopic compositions. Based on these data, it is shown that the mafic rocks may have resulted from melting of metasomatically enriched lithosphere, whereas the silicic magmas represent partial melts of ancient lower crust and late Mesozoic magmas underplated at the crust-mantle boundary (Ling et al., 2009).