北祁连东段西、南华山中酸性侵入岩地球化学特征  

Geochemical characteristics of the mid-acidity intrusive rocks in Nanhuashan and Xihuashan in the eastern segment of North Qilian Mountains,China

作　　者：姚志刚[1] 高珊[1] 王永东[2] 佘刚[1] 

机构地区：[1]西安石油大学油气资源学院,陕西西安710065 [2]延长油田股份有限公司,陕西延安716000

出　　处：《西安石油大学学报（自然科学版）》2010年第5期37-41,共5页Journal of Xi’an Shiyou University（Natural Science Edition）

基　　金：陕西省自然科学基金项目(编号:SJ08D03);中国博士后科学基金项目(编号:20070420214)

摘　　要：北祁连东段西、南华山中酸性侵入岩以花岗岩和花岗闪长岩为主，SiO2质量分数在66．23％～77．13％之间，具有钙碱系列的岩石组合特征和地球化学特征．微量元素Pb、Sr和La明显富集，Cs、Nb、Ti等元素呈现不同程度亏损，显示混合源岩浆的特征．∑REE的质量分数为（100．80～121．03）×10^-6，低于世界酸性岩平均值．稀土配分模式呈右倾型，δEu=0．31～0．33，有负Eu异常，与北秦岭加里东期岛弧型花岗岩地球化学特征相似．中酸性岩体总体表现为壳幔混合型岩浆结晶分异的产物，反映北祁连地区中奥陶世末处于具沟一弧一盆体系的俯冲背景．The mid-acidity intrusive rock in the studied area is mainly composed of granite and granodiorite,in which the mass fraction of SiO2 is 66.23% ~ 77.13%,and it is of the association characteristics and the geochemical characteristics of calc-alkaline rock series.In the intrusive rock,trace elements Pb,Sr,and La are enriched,while the elements Cs,Nb and Ti are lean in different degrees,which show the characteristics of mixed source magma.The total content of rare elements is 100.80~121.03 μg/g,which is lower than the world average value of acidic rocks.REE distribution pattern presents right dip type,δEu is in 0.31 ~ 0.33,and there is negative anomaly of Eu,which is similar to the geochemical characteristics of the island-arc granite from the northern Qinling in the Caledonian stage.In a whole,the mid-acidity intrusive rock is produced by the crystallization differentiation of mixed crust-mantle magmatic,which reflects the dive background of trench-arc-basin system in the northern Qilian area in the end of Middle Ordovician.

关 键 词：北祁连 西 、南华山岩体 地球化学特征 构造环境 

分 类 号：P588.13[天文地球—岩石学]