The serpentinite of Dalabute ophiolitic mélange shows low TiO2，Al2O3，CaO and total alkali，high MgO，Mg#; and has low ∑REE，is enriched in LREE，the rare earth element distribution patterns appear “凹” or “U”. It is a depletion pyrolite form primitive mantle which had undergone partial melting. The geochemical of gabbo and basalt characteristics of low ∑REE， depleted in LREE and unfractionated in HSF elements indicate that it is similar to a normal midocean basalt （NMORB），meanwhile，the samples are enriched in largeion lithophile elements（LILE），depeleted in Nb and Ta on different degrees. It is indicated that the Dalabute ophiolitic mélange is a typical SSZtype ophiolite，associating with the new isotope age （391±6Ma），it is concluded that the main Western Junggar oceanic basin has begun to eliminate，and the continental plate has begun to converge in Middle Devonian.