内蒙古西部呼伦陶勒盖地区花岗岩类的初步研究  

A preliminary study of granitoids in western Inner Mongolia

作　　者：韩宝福[1] 张臣[1] 赵磊[1] 任荣[1] 徐钊[1] 陈家富[1] 张磊[1] 周印章[1] 宋彪[2] 

机构地区：[1]教育部造山带与地壳演化重点实验室,北京大学地球与空间科学学院,北京100871 [2]北京离子探针中心,中国地质科学院地质研究所,北京100037

出　　处：《岩石矿物学杂志》2010年第6期741-749,共9页Acta Petrologica et Mineralogica

基　　金：国家重点基础研究规划项目(2007CB411305);国家科技支撑计划重点项目(2006BAB07B08);中国地质调查局项目(1212010611803)

摘　　要：靠近中蒙边界的内蒙古西部呼伦陶勒盖地区的中元古界和石炭系中产出数个花岗岩体,其中以英格特-巴格毛道岩体的出露面积最大,岩性变化显著,包括石英闪长岩、花岗闪长岩和花岗岩,含有围岩的残留体,并被年轻的花岗岩和伟晶岩等侵入。以前的资料显示该岩体是晚古生代形成的,而其他红色的花岗岩和钾长花岗岩小岩体(如库楚乌拉和一连)是中生代形成的。SHRIMP锆石U-Pb定年结果显示,英格特-巴格毛德岩体的年龄为313±5Ma,相当于晚石炭世。原定为中生代的库楚乌拉和一连两个红色花岗岩体的年龄分别为277±2Ma和278±4Ma,相当于早二叠世,而侵入于英格特-巴格毛道岩体中的石英二长岩的年龄为130±2Ma,相当于早白垩世。晚石炭世花岗岩具有I-A型过渡的元素地球化学特征,而早二叠世花岗岩具有A型花岗岩的特征,属于铝质A型花岗岩。晚古生代花岗岩的共同特征是均以具正的εNd(t)值(0.90～3.43)为特征,具有新生地壳的性质,是内蒙古西部地区陆壳生长的标志。而早白垩世石英二长岩的εNd(t)值为-8.71,指示岩浆起源可能以壳源物质为主,有地幔物质参与。In the Huluntaolegai area of western Inner Mongolia,close to China-Mongolia border,several granitoid plutons occur in the Mesoproterozoic and Carboniferous country rocks,of which the Yinggete-Bagemaode pluton is the largest one.This pluton has greatly varied lithologies,composed of quartz diorite,granodiorite and granite,which contain abundant relicts of country rocks and have experienced intrusion of younger granites and pegmatites.According to previous data,the Yinggete-Bagemaode pluton may be Late Paleozoic in age,whereas other small plutons dominated by red granite and potassium feldspar granite such as the Kuchuwula and Yilian plutons,which occur within or to the west of the largest pluton,were possibly emplaced in the Mesozoic.Unfortunately,neither reliable chronological constraints nor geochemical data for these plutons are available.In view of this situation,the authors conducted a preliminary study of these plutons in order to determine their emplacement ages and geochemical characteristics.SHRIMP zircon U-Pb dating reveals that the Yinggete-Bagemaode pluton was emplaced at 313 ± 5 Ma （Late Carboniferous）,and this pluton was cut by the quartz monzonite at 130 ± 2 Ma （Early Cretaceous）,whereas the Kuchuwula and Yilian red granite plutons were emplaced at 277±2 and 278±4 Ma,respectively,suggesting products of Early Permian instead of Mesozoic magmatism.Geochemically,Yinggete-Bagemaode pluton shares characteristics of I-and A-type granites,with 10 000 Ga/Al of 2.15～3.04 and negative Ba,Nb,Ta,P,and Ti anomalies,while the Kuchuwula and Yilian plutons are aluminous A-type granites,showing significantly negative Ba,Nb,Ta,P and Ti anomalies and high 10 000 Ga/Al ratios （4.02～4.89）.All the Late Paleozoic plutons are characterized by positive εNd（t） values （0.90～3.43）,like the coeval granitoids in North Xinjiang,Mongolia,and Northeast China in this respect,and thus are indicative of crustal growth in the study area.In contrast,the Early Cretaceous quartz monzonite has significantly n

关 键 词：花岗岩类 锆石年代学 同位素 地壳生长 内蒙古 

分 类 号：P588.121[天文地球—岩石学] P597[天文地球—地质学]