【摘要】 阿尔泰造山带的库卫地区分布有10余个镁铁超镁铁质岩体,库卫岩体是其中面积最大的一个岩体。SHRIMP锆石U-Pb方法测年结果表明其形成时代为47±1Ma,暗示了该地区新生代曾发生过强烈的隆升过程。与阿尔泰山其他地区的镁铁超镁铁质岩体相比,库卫岩体的地球化学特征具有特殊性,以低的TiO2、稀土元素、不相容元素含量及高的Al2O3含量为特征。较大的MgO含量变化范围(6.6%~20.1%)以及MgO与其他主要元素和Ni含量之间的相关性暗示着岩浆发生过橄榄石、斜方辉石和单斜辉石的分离结晶作用。低的稀土和不相容元素含量及平坦型的稀土元素配分模式和不相容元素比值(如La/Sm和Gd/Yb)暗示了其原始岩浆来自于亏损的软流圈地幔(石榴石二辉橄榄岩)的高度部分熔融。同时,高的La/Nb比值和在微量元素原始地幔标准化图解上显示出的明显正Pb异常暗示着岩浆在岩浆房中曾遭受过下地壳物质的同化混染作用,岩体中较低的Ni含量则可能是深部硫化物熔离作用的结果。更多还原

【Abstract】 More than ten mafic-ultramafic intrusions are distributed in Kuwei area of the Altay orogenic belt, and the Kuwei intrusion is the biggest one in this area. The SHRIMP U-Pb zircon dating yields an age of 47±1 Ma, suggesting that strong uplift occurred in this area during Cenozoic. Compared with the mafic-ultramafic instrusions in other areas of the Altay Mountains, the Kuwei intrusion has some unique geochemical features in that it is characterized by low TiO-2, REE and incompatible element contents, and high Al₂O₃ contents. The wide range of MgO contents （6.6%～20.1%） and the correlation between MgO contents, other major element contents and Ni contents imply that the fractional crystallization of olivine, orthopyroxene and clinopyroxenemight have occurred.Its low REE and incompatible element contents ,flat chondrite-normalized REE patternsandincompatible element ratios （e .g.,La/Smand Gd/Yb） indicate that the pri mary magma resultedfromthehigh degree of melting of the depleted asthenospheric mantle （garnet peridotite） .In addition,its high La/Nbratios and the markedly positive Pb anomalies in the pri mitive mantle normalized trace element patterns suggestthat the magma must have been subjected to the contamination of lowcrust materials in the magma chamber .The relativelylow Ni contents probably resulted fromthe i mmiscible sulfide melt at a relatively deeplevel .更多还原