In the study area there exist two types of closely associated active epicontinental mantle-derived imrusive assemblages belonging to tholeiite series and calc - alkaline series respectively. Intrusive rocks of the two series show systematic chemical differences and generally experienced fractional crystallization of mafic minerals at the high magmatic chamber. Both the tholeiite series and the calc-alkaline series exhibit geochemical characteristics of mantle-derived magma along the margin of plate convergence, and are in different degrees enriched in large-ion lithophile elements and impoverished in high field strong elements, transitional elemenu and heavy rare earth elements. Geochemical studies show that magma of these two series originated from the same impoverished mantle source, with the source rock being spinet peridotite. The enrichmem of large-ion lithophile elements should be attributed to the devatering or melting of the subducting plate. The chemical differences between these two series resulted from the higher melting degree of the tholeiite series than that of the calc-alkaline series. They were both formed during the closing process of the Qinling paleooceanic basin in Dinning period.