新疆西准噶尔洪古勒楞蛇绿岩带堆晶岩岩石组合及特征

Rock Assemblage and Characteristics of Cumulate Rocks onHongguleleng Ophiolite Belt in Western Junggar,Xinjiang

新疆西准噶尔洪古勒楞蛇绿岩具有相对完整的岩石组合,从底部到顶部由变质橄榄岩、超镁铁质-镁铁质堆晶岩和火山岩组成,其中发育良好的堆晶岩是该蛇绿岩带的典型特征。洪古勒楞蛇绿岩带堆晶岩可分为超镁铁质堆晶岩和镁铁质堆晶岩两类,超镁铁质堆晶岩以纯橄岩为主,是堆晶岩中铬铁矿的主要赋存岩相;镁铁质堆晶岩包括橄长岩和辉长岩两种类型,橄长岩主要由橄榄石和基性斜长石组成,其中以橄榄石为主的称为暗色橄长岩,以基性斜长石为主的称为浅色橄长岩;辉长岩主要由单斜辉石、基性斜长石、橄榄石组成,根据橄榄石含量又可划分为富橄榄石辉长岩、橄榄辉长岩和辉长岩3种类型,镁铁质堆晶岩组成即是以橄榄石-基性斜长石-单斜辉石相组合的端元或过渡类型。

The Hongguleleng ophiolitein western Junggar,Xinjianghas relatively complete rock assemblages,which can be clas-sified into metamorphic peridotite,ultramafic-mafic cumulate and volcanic from the bottom to top. The well-developed cumulate rockisa typical characteristic of the ophiolite belt. The cumulate rocks can be classified into two types,i. e the ultramafic cumulate and themafic cumulate. The ultramafic cumulate is mainly composed of cumulate dunite,which is the major hosted lithofacies of chromite. Themafic cumulate consistsgabbroand troctolite whichis composed by olivine and bytownite. The troctolite is grouped intodark troctoliteandlight troctolite depends on it has more olivine or more bytownite. The gabbro consists clinopyroxene,bytownite,olivine and can be di-vided into three types according to the content of olivine: olivine-riched gabbro,olivine gabbro and gabbro.The mafic cumulate is theend-element or transition type of olivine-basic plagioclase-clinopyroxene.