The Wanbaogou Group of Upper Proterozoic to Cambrian age is located in southern East Kunlun Mts, around Nachitai on the Qinghai-Tibet Highway. The volcanic sequence lies in the midlower part of the Group with a thickness of greater than 1500m. The rocks comprise mainly basaltic lava, accompanied by some basic tuff. The components of the volcanics are relatively homogeneous, sugges- ting poor differeiiciation. Vesicular and pillow structures can be observed in the lavas, but they are not widely developed; lava breccias and carbonate interlayers are present in the tuffs. The pyroxenes were replaced by amphibole and chlorite,while the plagioclases had suffered from zoisitization and argilliz}tion. In addition,there are also some cases of silisification and carbonatization. The rocks are characterized by low content of SiO2 (less than 50%)and high content of Ti02(about 3%):and low Mg0(generally 4一5%)and high TFeO (about 14 %)contents. K20+Na20. and P205 contents are 2-4%and less than 0. 4% respectiv- ely. The trace element distribution is low in Cr and Ni (69-113pprrt and 23-71ppm respectively)，corresponding to the low content of Mg0，while the high V(256-383 ppm) and Zr(116-289ppm) contents are consistent with that of TFeO.The REE normalized values show a LRE-rich pattern, and 87Sr/86Sr values range between 0.702-0.705. The above data suggest that this volcanic suite was derived from tholeiite of deep origin and formed in an intraplate environment. It is somewhat .suballcaline in character and exhibits some features of oceanic islandtype basalt, indicating in the early history of the evolution of the East Kunlun crust there existed a significant extensional period as the initial stage of the formation of the East Kunlun eugeosyncli.ne.