白云鄂博海西期花岗杂岩体的稀土元素地球化学

Rare Earth Element Geochemistry of the Heicynian Granite Complex at Baiyunebo,Inner Mongolia,China

本文在综合研究白云鄂博海西期花岗杂岩体岩石学特征的基础上 ,系统地分析测定了该杂岩体不同阶段花岗质岩石的稀土元素、微量元素和铅同位素组成 ,提出杂岩体的形成演化由早到晚 ,从花岗闪长岩→中粗粒黑云母钾长花岗岩→细粒黑云母钾长 -碱长花岗岩 ,是下地壳古老变质岩石经部分熔融作用产生的岩浆经不同程度的分离结晶作用所形成。白云鄂博花岗岩属于同碰撞花岗岩 ,形成于蒙古板块与华北板块的碰撞期。白云鄂博花岗杂岩体的稀土元素和微量元素地球化学特征明显不同于白云鄂博 RE- Nb- Fe矿床赋矿白云石大理岩 ,暗示稀土元素的成矿作用与花岗岩岩浆活动没有直接的成因联系。

On the basis of study of petrological characteristics of the Heicynian granite complex at Baiyunebo,this paper systematically analyzes rare earth element,trace element and Pb isotope compositions of the different stage granites from the complex,and suggests that the granite complex,from the early to late stage,e.g.granodiorite→middle coarse grained biotite K feldspar granite→fine grained biotite alkali feldspar granite,is produced by fractional crystallization of the granitic magma derived from partial melting of the old lower crust.The Baiyunebo granites could be classified to be the type of syn collision granite,and is formed during the period of collision between the Mongolian plate and the North China plate.The rare earth element and trace element geochemistry of the granites are totally different from those of the ore hosted dolomite marbles in the Baiyunebo giant RE Nb Fe ore deposit,which imply that the RE mineralization of the deposit is not directly related to the granite magmatism.