内蒙古狼山乌和尔图花岗岩岩体锆石U-Pb年代学及地球化学特征  

ZIRCON U-PB CHRONOLOGY AND GEOCHEMICAL CHARACTERISTICS OF THE WUHEERTU GRANITE MASS IN LANGSHAN,INNER MONGOLIA

作　　者：王文龙 滕学建 刘洋[1] 滕飞 郭硕 何鹏[1] 田健 段霄龙 

机构地区：[1]中国地质调查局天津地质调查中心,天津300170

出　　处：《地质力学学报》2017年第3期382-396,共15页Journal of Geomechanics

基　　金：中国地质调查局地质调查项目<内蒙古1:5万查干呼舒庙;楚鲁庙;潮格;哈尔木格台;那仁宝力格公社;居力格台幅区域地质矿产调查>(编号:12120113056300)

摘　　要：乌和尔图花岗岩岩体位于华北板块北缘,内蒙古狼山地区,岩石类型主要为正长花岗岩及二长花岗岩。LA-ICP-MS锆石U-Pb年龄为236.1±1.0Ma,晚三叠世。岩石高硅(SiO_2为71.94~73.91%)、富碱(K_2O+Na_2O为8.34~8.88%)、弱过铝(A/CNK为0.98~1.07),贫钙、镁。在SiO_2-K_2O图中,样品点落入高钾钙碱性系列-钾玄系列的过渡区域。在原始地幔标准化蛛网图上,不同程度富集Rb、Th、K、Nd、Zr、Hf、Sm,亏损Ba、Nb、Ta、Sr、P、Ti,具中等-弱的负Eu异常(δEu=0.47-0.66)。主量元素、稀土元素和微量元素特征表明,乌和尔图花岗岩岩体形成于由挤压体制向拉张体制转换的构造背景,属后碰撞花岗岩类。锆石Hf同位素显示,乌和尔图花岗岩岩体的εHf(t)为-20.6~7.6,二阶模式年龄为780~2559Ma,变化范围较大,反映源区物质以古老地壳为主,可能有年轻组分的参与。对该岩体的综合研究有助于进一步认识和探讨华北板块北缘二叠纪末-三叠纪的构造-岩浆演化过程。The WuheErtu granite mass, with the m a i n rock types of syenogranite and monzogranite , are distributed in Langshan area, Inner Mongolia, northern margin of the North China Plate. Zircon U - P b ageis 236. 1 ± 1. O M a , indicating the WuherErtu granite mass formed in late Trias sic. Geochemical results show high content of Si0 2 （71. 94 -73. 91% ）,K 20 ＋ Na 20 （8. 34 -8. 88% ）,low content of C a and Mg , and w e a k content of a l u m i n u m （0. 98 〈 A/CNK 〈 1. 07 ） . In Si02-K 20 d i a g r a m, sample points fall into the transitional region between high-K calc-alkaline and Shoshonite series. In the primitive mantle-normalized spider d i a g r a m, the geochemical characteristics of the granite mass show in s o m e degree enrichment in R b、T h、K 、N d、Z r、H f、 S m and depletion in Ba、Nb、Ta、Sr、P 、Ti,with m e d i u m to negligible E u anomalies （ 8E u = 0. 47 -0. 66 ） ,which indicate the WuherErtu granite mass belong to the post-collisional granite formed in the tectonic setting transformed from compression system to extension system. Zircon H f isotopic displays that e H f （t） values vary from - 20. 6 to ＋ 7.6 and Hf model ages （ TDM 2 ） vary from 780 -2559 Ma,which suggest a mixed m a g m a source of oldcontinental crust with a small involvement of juvenile c o m p o n e n t s. T h e comprehensive study of this granite mass helps to further understand and explore the tectonic-magmatic evolution of the northern margin of the North China plate in late Permian- Triassic.

关 键 词：内蒙古 狼山地区 三叠纪花岗岩 后碰撞 地球化学 

分 类 号：P588.3[天文地球—岩石学]