The Proterozoic neritic volcanic series in the western part of the Qili an Mountains ar e products of continental rift volcanism, belonging to continental flood bas alts.A petrogeochemical study of them suggests that they are characte ri zed by high εNd and low (87Sr/86Sr)i and are de rived from sublithospheric mantle p lume sources, but there is also for involvement of continental lithosphere compo n ents.Their formation is the result of mantle plumelithosphere inte ractions and is precursive to the opening of the early Paleozoic oc ean basin of North Qilian.