内蒙大青山地区黑云母花岗岩SHRIMP U-Pb定年及其构造意义  

SHRIMP U-Pb dating of biotite granites in Daqingshan,Inner Mongolia, and its significance.

作　　者：张臣[1] 韩宝福[1] 刘树文[1] 季建清[1] 赵磊[1] 张磊[1] 

机构地区：[1]北京大学地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京100871

出　　处：《岩石学报》2009年第3期561-567,共7页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40772142,40872120)资助.

摘　　要：大青山黑云母花岗岩主要由钾长石(45%)、斜长石(15%～25%)、石英(25%)、黑云母(5%～10%)组成。主元素SiO_2含量69.48%～72.40%,K_2O+Na_2O含量7.74%～9.58%,K_2O>Na_2O,A/CNK为1.0～1.17,具过铝质-强过铝质花岗岩特征;稀土元素分馏较强,REE配分型式具中等负Eu异常;微量元素在原始地幔(PM)标准化蛛网图上显示Rb、Th、K、Nd相对富集,Nb、Sr、Ti相对亏损,岩石地球化学特征与碰撞花岗岩类似。本文对大青山地区料木山黑云母花岗岩进行高精度锆石SHRIMP U-Pb定年研究,其形成时间为2430±19Ma,可能代表鄂尔多斯陆块与阴山微陆块碰撞造山岩浆热事件年龄。区域上埃达克质岩、赞歧岩、Colcepet花岗岩同位素年龄均为2470～2330Ma,预示着这一地区在古元古代早期可能已经出现与板块消减相关的陆-陆碰撞造山带。古元古代花岗岩的岩石地球化学和同位素年代学特征表明乌拉山-大青山麻粒岩相带是一条古元古代造山带。The Daqingshan biotite granites consist mainly of orthoclase (45%), oligoclase (15% similar to 25%), quartz (25%) and biotite(5% similar to 10%) in the Daqingshan area of Inner Mongolia.. The biotite granites are characterized with SiO(2) (69.48% similar to 72.40%), K(2)O + Na(2)O (7.74% similar to 9.58%) contents, K(2)O > Na(2)O and A/CNK = 1.0 similar to 1.17, as well as fractionated BEE patterns with middle negative Eu anomalies. The biotite granites are relatively enriched Rb, Th, K, Nd and depleted Nb, Sr, Ti. These geochemical characteristics are similar to collision granites. Using high-precision SHRIMP U-Pb zircon dating method, We determine the Daqingshan biotite granites were formed at 2430 +/- 19Ma, the-results indicate that the collision event of Erduosi block with Yinshan block. Integrated with that the adakitic granitoids, sanukitiods, Closepet-type granitiods of Guyang and Wuchuan area displaced at 2470 similar to 2330Ma, and it indicating that subduction bearing an analogy to modern plate has taken on the Early Paleoproterozoic. Base oil the geochemistry and geochronology of the Palcoproterozoic granitiods, we suggested that the granulite terrain of Wulashan-Daqingshan is an Early Paleoproterozoic continent-continent collision orogenic belt.

关 键 词：古元古代花岗岩 SHRIMP锆石年龄 内蒙古 

分 类 号：P597.3[天文地球—地球化学] P588.121[天文地球—地质学]