Abstract: A rock assemblage resembling closely ophiolite is exposed in the Tomorit area in the eastern sector of the Caledonian rift zone on the northern margin of the Qaidam basin. Its geological and geochemical characteristics show that it does not have the nature of oceanic crust but should be an ophiolite like assemblage formed within continental crust, i.e. occurring in a continental margin rift environment without oceanic crust. This paper proposes a dynamic model different from that for the formation of ophiolite and points out that the ophiolite like rock in question is possibly a typical representative of the continental margin rift with oceanic crust.