During the Late Cretaceous the Taipingyan diabase porphyrite dikes with NNE strike emplaced into the eastern part of the Guidong composite granitoids in northern Guangdong Province. The dikes show enrichment in silicon (SiO2=53.91%~56.03%), alkaline (K2O=1.78%~3.02%), large ion lithophile elements including light rare earth elements without Eu anomaly (δEu=0.84~1.00) (LREE/HREE=9.35~10.24), and depletion in Nb, Ta, Zr and Ti. In addition, they have low εNd(91Ma) values (-5.8~-9.8), high n(87Sr)/n(86Sr) initial ratios (0.70899~0.71525) and Dupal anomaly of Pb isotope compositions. These geochemical features of the dikes were very similar to those of island arc volcanic rocks, though the dikes were formed within the intraplate environment. The cause for this is that the mantle source for the Taipingyan diabase porphyrite dikes was enriched through metasomatism of fluids originated from subduction of paleoPacific Ocean Plate and sediment which may have started in the Early or Middle Jurassic. Under the tectonic settings of crustal extension and lithosphere thinning in the Late Cretaceous such enriched mantle source with features between EMⅠ and EMⅡ members was subjected to partial melting, forming the Taipingyan diabase porphyrite dikes.