Early Paleozoic basic dike swarms are widely distributed in North Daba Mountain of South Qinling Belt. This paper reports zircon U-Pb age and whole-rock geochemistry for diabase dikes with the purpose of exploring their petrogenesis and geological significance. The results indicate that the dykes were emplaced during the late period of Early Silurian epoch (435~433 Ma). These diabases are characterized by low silica but high alkali and titanium content, exhibiting intraplate basalt geochemical characteristics with enrichment of light rare earth elements (LREE) and incompatible trace elements Ba, Nb and Ta but depletion of Rb, K, and heavy rare earth elements (HREE). The negative K and Rb anomalies indicate that amphibole or phlogopite was retained in the mantle source. Partial melting modelling result suggests that diabases were formed by high degrees of partial melting of an enriched spinel hornblendite source. In combination with geochemical characteristics and previous studies, the authors hold that the North Daba Mountain experienced large-scale extension during Early Paleozoic, and the extension of lithosphere induced the partial melting of metasomatized lithospheric mantle with low melting point and formed this alkaline magma belt.