Niumaoquan complex located in the east of late Paleozoic Harlik arc in Junggar plate contains magnetite. The complex has obviously stratified property and rhythmical tectonic characteristics, and the main rock types include olivine gabbro, olivine-bearing gabbro, gabbro and hornblende gabbro. Geochemical characteristics (m/f values of most rocks range from 0.65 to 1.44) indicate that Niumaoquan complex belongs to tholeiite series characterized by ferruginous basic-ultrabasic rocks. The concentrations of rare earth elements are relatively low, and the primitive mantle normalized REE patterns show rightly-oblique curve with slight enrichment of LREE. The rocks are enriched in large ion lithophile elements (Rb, Ba, Sr, U) and depletion of Nb,Ta and high field strength elements (Zr,Hf) with weak enrichment of Ti. Nd-Sr isotopic characteristics[εNd(t)=-3.4～-0.50,εSr(t)=-3.4～8.5] with the evolutionary trend towards EMⅠ indicate that the magmatic source was the enriched lithospheric mantle transformed by the subduction fluid. The complex was formed by Early Permian post-collision extention which occurred in northern Xinjiang. Delamination of lithospheric mantle resulted from partial melting caused by heating action of the asthenospheric material. At the same time, the material of enriched lithospheric mantle moved upward through the space formed by delamination of the lithosphere.