昆仑造山带中段蛇绿混杂岩的地质地球化学特征

昆仑造山带中段蛇绿混杂岩由镁质超基性岩、块状辉石质玄武岩、枕状玄武岩、堆晶岩、斜长岩脉、灰岩岩块及其间的薄层状粉砂质泥岩、泥质粉砂岩组成 ,并有硅泥组合。不同岩性之间、不同块体之间由剪切带分开 ,沉积岩显示出浅深水岩块的混杂。其岩石化学主要特征是MgO含量特别高 ,达 33.2 2 %～ 37.2 8% ,SiO2 、CaO、Al2 O3 、TiO2 、K2 O含量低 ,FeO /(FeO 十MgO)、Ca/Al2 O3 比值非常低。属镁质超基性岩。超基性岩的常量元素、微量元素 ,以及稀土元素特征表明 ,其形成的环境为多硅铝质陆壳成分的大陆边缘盆地 (具有洋脊及岛弧的过渡性质 )。

GEOLOGICAL AND GEOCHEMICAL CHARACTERISTICS OF THE OPHIOLITE COMPLEX IN THE CENTRAL SECTION OF THE KUNLUN MOUNTAINS

The ophiolite in the central section of the Kunlun Mountains was formed in Early Carboniferous, consisting of magnesium ultrabasic rocks, blocky pyroxene basalts, pillow basalts, cumulates, plagioclase dikes, carbonate rock bodies interbedded with thin-bedded silty mud rocks, argillaceous silts and silicon-mud combinations. The different lithologies and rock bodies are separated from one another by shear zones. The content of MgO is very high, which is 33.22%-37.28%. The contents of SiO 2, CaO, Al 2O 3, TiO 2, K 2O are low. The ratios of FeO~*/(FeO~*+MgO), Ca/Al 2O 3 are also very low. So the ophiolite belongs to magnesium-rich ultrabasite. The formation environment for the ophiolite is continental margin basin that is rich in sial crustal composition, and show the transitional characteristics from ocean ridge to island arc.