Petrogenesis of the basalt of Zhanjin Formation in the Gangmar Co area, southern Qiangtang, and its tectonic implications

There are widespread basic dykes and basalt distributed on the southern side of the Lungmu Co-Shuanghu-Lancang River suture zone trending nearly EW in southern Qiangtang. Basalts occur as interlayers in the Zhanjin Formation. Whole-rock compositions show that the southern Qiangtang basalts are alkaline and rich in Fe + Ti, and exhibit relative enrichment of light rare earth elements (LREE). Based on geochemical diagrams, the authors infer that the southern Qiangtang basalts erupted in an intraplate environment. It is concluded that the basalts in southern Qiangtang were related to the Permian mantle plume activity. The results achieved by the authors provide convincing evidence for the existence of the late Paleozoic mantle plume in southern Qiangtang.