内蒙古锡林浩特、林西地区三叠纪过铝质花岗岩的成因及构造意义  

Petrogenesis and Tectonic Significance of Triassic Peraluminous Granitoids in Xilinhaote and Linxi Area,Inner Mongolia

作　　者：叶栩松[1,2] 廖群安[3] 葛梦春[3] 

机构地区：[1]中国地质大学研究生院,武汉430074 [2]广西壮族自治区遥感中心,南宁530023 [3]中国地质大学地球科学学院,武汉430074

出　　处：《地质科技情报》2011年第3期57-64,共8页Geological Science and Technology Information

基　　金：中国地质调查局华北地区基础地质调查项目(1212010510507)

摘　　要：在兴蒙造山带中段的内蒙古锡林浩特、林西地区新拟定了两条近东西向展布的过铝质花岗岩带,单颗粒锆石U-Pb表面年龄为(248.3±7.1)～(238.1±7.4)Ma,是印支期岩浆活动的产物。这套过铝质花岗岩岩性组合为花岗闪长岩和二长花岗岩,在岩相学特征上,呈浅灰-灰白色,暗色矿物含量低,部分岩体具淡色花岗岩的特点,并出现白云母和电气石等富铝矿物。岩石地球化学特征上属过铝质的高钾钙碱性系列,其高SiO2,低MgO、FeOT、CaO,高K2O及w(K2O)/w(Na2O)的特征,与典型的S型花岗岩特征类似,在主、微量元素的构造环境判别图中大部分落入同碰撞花岗岩区。结合新近有关该区微古化石、蛇绿岩及花岗岩方面的研究进展,认为兴蒙造山带是一多旋回造山带,三叠纪过铝质花岗岩是晚海西-印支旋回晚期的产物,即西伯利亚板块和华北板块最终的对接时间为三叠纪。This article newly plots out two belts of nearly east-westward peraluminous granitoids in Xilinhaote and Linxi area,Inner Mongolia,the middle of Xin′an-Mongolia orogen,North China.Zircons from four granite samples were dated using LA-ICP-MS method.A weighted average apparent age of（248.3±7.1）-（238.1±7.4） Ma（206Pb/238U） is attained,equal to the Indosinian era,which represents the crystal age of the source rocks of granitoids.The rock association of the peraluminous granitoids is granodiorite and monzogranite.Petrographically,with light grey to grey color and low dark minerals,some of the granitoid samples contain aluminous-rich minerals,such as muscovite and tourmaline,presenting the features of leucogranitoids.The petrochemical and geochemical characters of the peraluminous granitoids show peraluminous high-k calc-alkaline,with high SiO2,low MgO,FeOT,CaO,high K2O content and K2O/Na2O ratio,which are similar to the typical S-type granitoids.Most of the peraluminous granitoids are plotted in syn-collision granitoids field on the main and trace elements tectonic discrimination diagram of the peraluminous granitoids.Combining with the research advances in microfossils,ophiolites and granitoids in this area,the author concludes that Xing＇an-Mongolian orogenic belt is a multicycle orogenic belt,the Triassic peraluminous granitoids are the products of the last stage during the late Hercynian-Indosinian cycle,namely,the Siberia Plate and the North-China Plate was convergent in Trias.

关 键 词：三叠纪 过铝质 S型花岗岩 锡林浩特 林西 

分 类 号：P588.121[天文地球—岩石学]