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 EM I 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 litho-sphere.%牛毛泉基性杂岩体位于准噶尔古板块博格达-哈尔里克晚古生代岛弧东段,赋存磁铁矿.研究表明,该岩体具有明显成层性和韵律构造特征,主要岩石类型有橄榄辉长岩、含橄榄辉长岩、辉长岩和角闪辉长岩.岩石地球化学特征表明,该套岩石属拉斑玄武岩系列,m/f值介于0.65～1.44之间,属铁质基性-超基性岩.岩石稀土元素总量相对较低,稀土元素配分曲线为轻稀土元素略富集的右倾型；岩石富集大离子亲石元素(Rb、Ba、Sr、U),相对亏损高场强元素(Zr、Hf),具有明显的Nb、Ta负异常和弱的Ti正异常.岩石εNd(t)=-3.4～-0.50,εSr(t)=-3.4～8.5,具有向EM I方向演化的趋势,表明岩浆源区可能为受俯冲流体交代改造的富集岩石圈地幔,是新疆北部早二叠世时期后碰撞伸展阶段的产物,由拆沉的富集岩石圈地幔被软流圈加热后发生部分熔融并上侵形成.
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