Early Ordovician mafic dykes exposed in thenorth Kunlun are of great significance for understanding the subduction processes and dynamic background of the paleo- active continental margin. In this paper, we present detailed petrology, zircon U- Pb chronology, whole- rock geochemistry and Sr- Nd isotopes of the mafic dykes. Zircon U- Pb dating results show that the zircon U- Pb ages of these dykes range from 486 to 483 Ma, suggesting an Early Ordovician age. Whole- rock geochemical results show that the mafic dykes have low SiO2 (50. 06%~51. 68%), medium MgO (5. 08%~6. 77%) and TiO2 (0. 99%~1. 20%) content, and belong to the tholeiitic basalt series. Regarding trace and rare earth elements, the rocks are enriched in large- ion lithophile elements (e. g. , Rb, Sr, Ba, Th, K) and depleted in high- field- strength elements (e. g. , Nb, Ta, Ti). The chondrite- normalized REE diagrams are featured by weak enrichment of LREE and depletion of HREE, with weak Eu anomaly. In addition, the dykes show high (87Sr/86Sr)i (0. 7126~0. 7133) and relatively low εNd(t) isotopic composition (9. 80~4. 31) of the enriched lithospheric mantle. The petrogenesis research indicates that the basic magma originated from the enriched lithospheric mantle, was metamorphosed by fluids in the subduction zone, and subsequently experienced fractional crystallization mainly of olivine and clinopyroxene during the diagenetic processes. Based on the regional geological data, we argue that the Kunzhong Ocean subducted northward in early stages of the Early Paleozoic and formed a magmatic arc system. It may have experienced the retreat of the subducting oceanic slab at 486 Ma, leading to an extensional tectonic setting in the upper plate of the subduction zone and then generation of mafic dykes.