Objectives: Mafic dykes mainly formed in intraplate extensional or mantle plume environments, and have important indicative significance of tectonic setting. A large number of mafic dykes occurred in the Zhongtiao Mountains, southern margin of North China Craton (NCC), which had a great bearing on the Paleoproterozoic tectonic evolution of NCC. This paper focuses on the metamorphosed mafic dykes intruded into the Jiangxian Group in Zhongtiao Mountains. Methods: Based on detailed field investigation and systematic petrology, the paper mainly researches its features of the geochemistry and chronology. Here we present new geochemical and high- precision LA- ICP- MS zircon U- Pb data from the metamorphosed mafic dykes, which help to constrain the timing, petrogenesis and tectonic setting. Results: The zircons yielded a upper intercept age of 1847±14 Ma, which is interpreted as the metamorphic age, and its intrusion age should be 1.85~2.14 Ga. Geochemical analysis indicates that the mafic dykes is characterized by low SiO2(45.94%~51.69%), TiO2(0.93%~1.09%), K2O (0.15%~0.46%) and high Fe2O3T (11.18%~13.43%), belonging to tholeiite series. The dykes are slightly rich in LREE, and weakly positive Eu anomalies (δEu=0.99~1.29), enriching in LILE (Rb, Ba La), as well as depleted in HFSE (Nb, Ta, Zr, Hf). The protolith of mafic dykes were possibly tholeiite with a continental affinity, and the magma source mantle shows the E- MORB nature. Conclusions: The Paleoproterozoic metamorphosed mafic dykes in Zhongtiao Mountains was partially melted from enriched mantle source, which was effected by crust materials within the source and it may be effected by fluids in subduction zones.1.85~2.14 Ga magma activity indicated there was an intense extensional event in North China Craton after the cratonization at the end of Archean, and experienced intensive metamorphism at about 18.5 Ga.