This paper focuses on the lower Gangdagai Formation in the south of the Zhongza landmass. The results show that the strata are dominated by mixed basaltic breccia - tuff lava, microcrystalline basalt, and basaltic breccia tuff, and characterized by rich alkali, high titanium content, and strong enrichment of light rare earth elements. They are the products of the low-degree molten mantle, belonging to tensile fracture volcanic rocks within a continental plate. They share similar geochemical characteristics with Emeishan basalt (Pe) in the neighboring region to the east, implying the affinity between their mantle sources as well as a relationship with mantle plume activities.