A large volume of ultrabasic to basic dikes and alkaline volcanic complexes, widely occurring in the Early Paleozoic strata in the North Daba Mountains, provide a good opportunity to explore the nature of mantle and tectonic evolution of the South Qinling and the North Daba Mountains. The ages of these rock assemblages are still controversial. In this paper, zircon U-Pb dating and phlogopite 40Ar/39Ar isotopic dating are used to constrain the age of these rock assemblages. The Langao and Zhenping diabases are dated at 399±1 Ma and 451±4 Ma, respectively, using the zircon U-Pb dating technique, which so far are the youngest and oldest ages for the basic dikes. Geochemical data show that both Langao and Zhenping diabasses have OIB signature, enriched in LREE, LILE, Nb and Ta. They are plotted on the same linear variation tendency and have similar Primitive-normalized trace elements spider diagram indicate that they are originated from a same mantle source. Therefore, the emplacement of ultrabasic to basic dikes began at Katian of Late Ordovician (~450 Ma), ended at Emsian of Early Devonian (~400 Ma), with several peaks of magmatic intrusions. The phlogopites from the volcaniclastic rocks are dated at 446±3 Ma, using the 40Ar/39Ar isotopic dating method, which represent the age of volcanic activity. This age is consistent with the emplacement age of basic dikes within uncertainty, indicating that they started at the same time. Although the exact ages of the trachytes are not obtained, the younger zircon ages (165±3 Ma and 229±2 Ma) imply that they may be formed in Mesozoic. Systematic dating results show that the ultrabasic to basic dikes and alkaline basalts are originated from a same magmatic source, and magmatic activity started at 450 Ma, last till ~400 Ma. The trachytes, however, may be formed in Mesozoic and represent the products of Mesozoic magmatism in South Qinling orogenic belt. There is no Early Silurian bimodal volcanic rock in the North Daba Mountains.