中文摘要：

柴北缘冷湖盐场北山镍铜矿区发育辉长岩和角闪辉长岩,属亚碱性岩石系列.球粒陨石、原始地幔标准化曲线呈两组特征,但配分型式基本-致,反映其来自同-源区.稀土标准化曲线表现为弱右倾型,Eu基本无异常,说明斜长石分离结晶作用不明显.Rb、Nb、Zr、Cr等微量元素丰度及比值具有近似平行部分熔融的演化趋势.结合岩体Mg#值和岩体固结指数（SI）高等特点,揭示原始岩浆具有幔源原生玄武岩浆特征,认为其成因与俯冲板片流体交代地幔楔源区的部分熔融有关,而且,Nb、Zr、Y元素丰度表明辉长岩源区为过渡型地幔.另外,两类岩体强烈亏损Nb、Ta、Zr、Hf、Ti等高场强元素（HFSE）,富集Ba、Th、U、Pb等大离子亲石元素,反映明显的消减带和岛弧环境岩浆岩典型特征.LA-ICPMS锆石U-Pb测年结果表明辉长岩形成于254±3 Ma,结合该时期区域地质构造背景,认为柴北缘晚二叠世处于俯冲作用之下的岛弧构造环境,具有活动大陆边缘性质.

英文摘要：

The gabbro and hornblende gabbro are widely occur at the nickel-copper mining area of Yanchangbeishan in Lenghu,which located in the west segment of the north margin of Qaidam.The Rittmann index of the rocks show they belong to sub-alkaline series.The chondrit and primitive mantle-normalized curve show two group characteristics,but have similar partition pattern,which indicate they came from the same magmatic source.The REE standard curve show weak right dip type and no Eu anomalies nearly,that may reflect weak fractional crystallization of plagioclase.The abundance and ratio of Rb,Nb,Zr,Cr show the evolution trend of partial melting.Combined with the fairly high Mg# and SI,the primary magma have a feature of primary basaltic magma.It is believed that the magma originated by partial melting,based on the subduction slab fluid metasomatized mantle wedge,and the abundance of Nb,Zr,Y imply the rocks derived from transitional mantle source.Moreover,these samples are low HFSE （Nb,Ta,Zr,Hf,Ti）,high LILE （Ba,Th,U,Pb）,reflecting the typical characteristic of subduction zone and island-arc magma.LA-ICPMS zircon U-Pb dating shows that the formation age of the gabbro is 254±3 Ma.Based on the regional geological background,we consider that the north margin of Qaidam was in volcanic arc or active continental margin tectonic environment during Permian epoch.