【摘要】 西昆仑西北缘柯牙吾齐超镁铁岩的发现对于西昆仑西段构造演化研究和相关矿产资源的探寻具有重要意义。本文对该超镁铁岩7件样品进行了镜下鉴定、主量和微量元素分析，结果显示：超镁铁岩呈断续脉状产出，岩性主要为蛇纹石化辉橄岩；具有相对低SiO₂（42.14%～47.43%）、低TiO₂（0.03%～0.24%）、高MgO（24.69%～31.22%）、高FeO^T（7.05%～11.65%）、贫碱（K₂O+Na₂O=0.55%～0.88%）的特征；Mg^#值为79.98～86.70;样品的m/f比值介于3.96～7.82;样品中稀土总量（∑REE）不高(11.41×10^-6～17.84×10^-6),轻重稀土比值LREE/HREE为2.81～5.69;δEu显示弱的Eu正异常；相容元素Ni、Cr和Co含量高。在微量元素原始地幔标准化蛛网图上，表现为富集大离子亲石元素（LILE）Rb、Ba、U、Sr和Pb,相对亏损高场强元素（HFSE）Nb、P、Zr、Hf、Ti等，显示轻稀土富集的特征。结合区域构造背景分析认为，晚三叠世，古特提斯洋的闭合引起碰撞后伸展，来自亏损地幔岩浆受前期俯冲流体或者熔体改造，沿着深断裂上侵，过程中经历了一定程度的地壳混染，最终形成柯牙吾齐超镁铁岩。更多还原

【Abstract】 The discovery of ultramafic rocks in the northwestern margin of west Kunlun is of great significance for discussing the tectonic evolution and related mineral resources potential in the western section of west Kunlun. This work conducted microscopic identification, and major and trace element tests on seven ultramafic rock samples. Results show that the ultramafic rocks occur as intermittent veins, and are dominated by serpentinized pyroxene peridotite. The ultramafic rocks are characterized by relatively low SiO₂（42.14%～47.43%）,low TiO₂（0.03%～0.24%）,high MgO（24.69%～31.22%）,high FeO^T（7.05%～11.65%）and low alkali（K₂O+Na₂O= 0.55%～0.88%）. Mg^# values range from 79.98 to 86.70. The m/f ratio of the samples lies in a range of 3.96～7.82. The total amount of REE（∑REE）in the samples is not high(11.41×10^-6～17.84×10^-6),and the LREE/HREE ratio is 2.81～5.69. δEu shows weakly positive Eu anomaly. The content of compatible elements（Ni, Cr and Co）is high. In the primitive mantle-normalized spider diagram of trace elements, they are enriched in LILE（Rb, Ba, U,Sr and Pb）,and relatively depleted in HFSE（Nb, P,Zr, Hf, Ti, etc.）,indicating the enrichment of light rare earth elements. Combined with regional tectonic setting, it is suggested that the closure of the Paleotethys ocean resulted in the extension after collision in the Late Triassic, and the magma from the loss mantle was transformed by subduction fluid or melt in the early stage, and intruded along deep fault, which experienced certain crust mixing in the process to finally form the Keyawuqi ultramafic rocks.更多还原