The systematic investigations and studies of the back-arc basin magmatism can provide important information for exploring the crust-mantle interaction at the converging plate margin, plate subduction dynamics, and the formation-evolution mechanism of back-arc basins. This paper presents a comprehensive study of petrography, zircon U-Pb chronology, rock geochemistry and isotope geology for the Permian mafic rocks recently discovered in the northern Yushu area, and the data could offer key clues to understand the formation mechanism of continental back-arc basins and the origin of mafic magmas. The zircon LA-ICP-MS U-Pb dating results show that the crystallization age of the gabbro is 260±1 Ma.The basalt samples have relatively low TiO₂ content and Nb/Y ratio and relatively high Ce/Nb ratio. Compared with the primitive mantle, those samples are significantly enriched in elements such as light rare earth elements and Th, and depleted of Nb, Ta, Ti, and P, etc., which are similar to the composition characteristics of typical back-arc basin basalts (such as the Okinawa Trough BABBs) in the world. The gabbro samples have relatively high TiO₂ content and Nb/Y ratio and relatively low Ce/Nb ratio. Those samples are significantly enriched in elements such as light rare earth elements and Th, and slightly depleted in Nb, Ta, and Ti, which could be comparable to those of OIB. The basalt samples have variable I_Sr (0.706~0.709) and εNd(t) (-1.8~+1.3), while the gabbros samples have relatively uniform I_Sr (0.709) and εNd(t) (-1.8~-1.5). Based on the results of this study, it can be concluded that the basalts should be derived from a lithospheric mantle modified by subducted components, while the gabbros might be originated from a mantle plume-related source. Combining with new regional studies, we propose that the mafic rocks in the study area should be formed in a continental back-arc basin environment, and the formation of the back-arc basin could be attributed to the slab-rollback caused by the deep oceanic subduction and the activity of the Emeishan mantle plume.