The East Kunlun Orogenic Belt is characterized by intense Hercynian–Indosinian magmatic activities, with widespread intermediatefelsic intrusions as well as large numbers of diabase dykes. Compared to the research of intermediateacid intrusions, however, less focus has been put to that of dabase dykes. In this study, a systematical research has been done to the chronology and geochemistry of mafic dykes, which determined the emplacement age, the tectonic setting as well as the petrogenesis of diabase. SIMS zircon UPb dating indicated that these dykes were formed in 227.5±3.3 Ma (1σ, MSWD=2.0)belonging to late Triassic, which well constrains the upper limit of emplacement of oreforming intrusions. Combined with our unpublished age data, a time span between 232Ma and 227.5Ma was further proposed to limit emplacement time of the oreforming intrusion of the Weibao skarn copperleadzinc deposit. The major elements of diabase in the Weibao deposit are characterized by high SiO2and K2O, and low MgO, Al2O3, CaO, FeO and Na2O, illustrating that most samples are calcalkaline rocks. The light and heavy rare earth elements(REE)are characterized by high fractionation, with LaN/YbN>5 and most δEu ranging from 0.73 to 0.77; therefore, in the chondritenormalized REE diagram, most samples are typical of rightdipping REE distributions with noticeable negative Eu anomaly; in the trace element spider diagram, these diabase selectively enriched LILE(e.g., LREE)and depleted HFSE(e.g., Ti, P). In spite of these arclike features showed by geochemical compositions of diabase, we argue that diabase in the Weibao deposit formed in a postcollision environment; the arclike features were probably derived from the enrichment by early subduction materials. In late Indosinian, upderplating of mantlederived magmas caused the partial melting of lower crust that produced felsic magmas; two source magmas mixed during rising and finally formed granodiorite and diabase sharing similar ages as well as rare earth and trace element compositions.