祁连山西段蛇绿岩型超基性岩特征及其地质意义

本文对祁连山西段具有代表性的大拉排沟等6个超基性岩体的岩石学,主要元素、微量元素及副矿物铬尖晶石特征作了深入的研究,认为分布于祁连造山带的蛇绿岩型超基性岩,具有分异后的上地幔组成特点,其成岩作用比较复杂。岩体主要由方辉橄榄岩和纯橄榄岩构成,为钙碱性系列的镁质超基性岩类。岩石化学成分具高MgO、Na₂O,而低Al₂O₃、Fe₂O₃、TiO₂、CaO、K₂O特征。同时,微量元素分析表明,该类岩体均起源于分异作用相对较小的深部地幔。

CHARACTERISTIES AND SIGNIFICANCE OF ULURABASIX ROCKS WITHIN OPHIOLITIC SEQUENCE IN TH WEST QILIAN

The Characteristics of petrology,major and trace elements and chrome spinel for the six typical ul-trabasic bodies within the ophiolitic sequence at Dalapaigou,West Qilian,have been thoroughly studied. It is concluded that the ophiolitictyped ultrabasic rocks from the Qilian orogenic belt, whose diagenesis is comparatively complex,are and all of them are mainly composed of Harzburgite and olivine and are mag-nesian ultrabasic rocks and fall under calcakaline Series, Compositionally having relatively high mgo , Na2O and low A12O3 ,Fe2O3 ,TiO2 ,CaO,K2O Contents Showing the rocks result from the differentiation of upper mantly. the result from the analysis of frace elements suggest that the rock bodies originate from the deep mantle having relatively weak diffrentiation.