内蒙古阿拉善右旗金长山早二叠世花岗闪长岩锆石U-Pb年代学及地球化学特征  

SUBDUCTION-RELATED EARLY PERMIAN GRANODIORITE IN JINCHANGSHAN OF ALASHAN,INNER MONGOLIA:EVIDENCES FROM ZIRCON U-Pb GEOCHRONOLOGY AND GEOCHEMISTRY

作　　者：陈炜[1,2] 周文平[2] 陈开旭[3] 刘明文[2] 王彤[2] 方明[2] 贺慧燕 张斌[2] 

机构地区：[1]中国地质大学地球科学学院,湖北武汉430074 [2]湖北省鄂东北地质大队,湖北孝感432000 [3]中国地质调查局武汉地质调查中心,湖北武汉430022

出　　处：《矿物岩石》2013年第4期53-60,共8页Mineralogy and Petrology

基　　金：内蒙古自治区阿拉善右旗月井子等五幅1:5×104区域矿产地质调查;项目编号NMKD2008-25

摘　　要：金长山侵入体位于内蒙古阿拉善右旗，为花岗闪长岩，岩石具钙碱性特征，w（SiO2）在63．33％～67．47％之间，K20／Na2O=0．84～0．95，相对富钠，A／CNK=0．90～1．17，w（Al2O3）变化于14．85％～15．68％之间，花岗闪长岩稀土元素总量∑REE变化于12．99×10^-6～70．24×10^-6之间；轻稀土元素富集，负Eu异常不明显，δEu=0．68～1．11；富K，Rb，Ba，Th等大离子亲石元素和亏损Nb，Y，Yb等高场强元素为特征。岩石学和岩石地球化学研究表明，该时期的花岗闪长岩具I型花岗岩和S型花岗岩的双重特征，形成于塔里木一华北板块与西伯利亚拼舍后拉张下的火山弧环境。用LA—ICP—MS法测试了金长山花岗闪长岩锆石的U—Pb年龄为294．6Ma±1．6Ma。暗示着在二叠纪早期本地区岩浆存在着剧烈地活动，是塔里木-华北板块与西伯利亚板块拼合后拉张作用的结果。Granodiorite rock with calc-alkaline characteristics occurred in Jinchangshan of Alas- han in Inner Mongolia. Content ofw（SiO2） ofthegranodioriteis63.33%-67.47%, K2O/Na2O =0.84-0.95,relatively rich in sodium, A/CNK=0.90-1.17 ,w（Al2O3） varied from 14.85% to 15.68%, belongs to metaluminous rocks. Y, REE change between12. 99 ×10 6470.24×10^-6 en- riched with light rare earth elements, with not obvious negative Eu anomaly（3Eu=0.68- 1.11）; rich in K,Rb,Ba, Th and other large ion lithophile elements and loss of Nb, Y, Yb in high field strength elements, Petrological and geochemical studies show that,Granodiorite formed the period is of dual characteristics of diorite and granodiorite granite of I type and S type. It formed in the condition of volcanic arc of post collision of Tarim plate, North China plate and Siberia plate. LA- ICP MS dating yields a 294.6 Ma± 1.6 Ma age, implying intense magmatic activity in the early Permian.

关 键 词：早二叠世花岗闪长岩 LA—ICP—MS U—Pb年龄 锆石 地球化学 金长山 内蒙古 阿拉善右旗 

分 类 号：P588.122[天文地球—岩石学] P597.3[天文地球—地质学]