Abstract:In this paper, analyses of major elements and trace elements for mafic dikes in several rock areas of the Zibo basin in West Shandong Province are reported. The K Ar ages of the dikes range between 72.16 Ma and 116.3 Ma, indicating that the mafic dikes are part of the result of Late Mesozoic magmatism. Based on petrology and geochemistry, the genesis and the source features of the dikes were studied. As a whole, the dikes are attributed to the calc|alkaline series in terms of major elements. As regards trace elements characteristics, the dikes resulted from partial fusion of mantle source rock and, at the same time, might undergo fractional crystallization of ol, cpx, Ti-Fe oxide and weak plagioclase during the lithogenic process. 208 Pb / 204 Pb =36.308~38.329, 207 Pb / 204 Pb =15.170~15.632 and 206 Pb / 204 Pb =16.658 ~18.470,are similar to those of the lower crust, indicating that there exist a lot of lower crust material in the reservoir. During emplacement, magmas were not subjected to crustal contamination, but the dikes are controlled by the collapse of the Yanshanian orogenic belt and the action (left handed advection and extension) of the Tanlu fault, showing characteristics of CABM. This shows that there existed subduction of the paleo ocean plate (the Su Lu ocean) (namely paleosubdution) before magmatism.