内蒙古格勒敖包奥陶纪岩体锆石U-Pb年龄及地球化学特征  

Zircon U-Pb age and geochemical characteristics of Ordovician pluton in Geleaobao,Inner Mongolia

作　　者：曹磊 苏茂荣[1] 周飞 李磊[1] 杨宝宏 CAO Lei;SU Maorong;ZHOU Fei;LI Lei;YANG Baohong(Inner Mongolia Key Laboratory of Magmatic Mineralization and Ore-Prospecting/Geological Survey Institute of Inner Mongolia, Hohhot 010020, Inner Mongolia,China)

机构地区：[1]内蒙古自治区岩浆活动成矿与找矿重点实验室/内蒙古自治区地质调查院,内蒙古呼和浩特010020

出　　处：《地质通报》2019年第4期632-642,共11页Geological Bulletin of China

基　　金：中国地质调查局项目<二连-东乌旗成矿带西乌旗和白乃庙地区地质矿产调查>(编号:DD20160041);<内蒙古1:5万阿格廷查干陶乐盖等六幅区域矿产地质调查>(编号:DD2016041-17)

摘　　要：内蒙古格勒敖包位于兴蒙造山带内,对该区奥陶纪岩浆岩的研究,有助于进一步认识该造山带早古生代的构造格局及其演化。正长花岗岩和斑状二长花岗岩样品LA-ICP-MS锆石年龄为441.6±3.7～454.9±4.6Ma,形成时代为奥陶纪。经地球化学分析,岩体为高钾钙碱性系列;铝饱和指数显示其为过铝质花岗岩。岩石富集大离子亲石元素(LILEs)Rb、Th、U、K,亏损Ba、Sr;富集高场强元素(HFSEs)La、Ce、Nd、Zr,亏损Nb、P、Ti;稀土元素总量为38.7×10^(-6)～120.23×10^(-6),轻稀土元素较重稀土元素分异明显,分馏程度较高,表现出较弱的负Eu异常。综合区域地质资料,认为格勒敖包奥陶纪岩浆源区为上地壳物质的部分熔融,其形成环境为弧后盆地,在古亚洲洋向北俯冲之后经历了岛弧岩浆作用旋回,为弧后伸张阶段的产物。The Geleaobao area of Inner Mongolia is located in the Xingmeng orogenic belt. By studying the Ordovician magmatic rocks in this area, researchers can further understand the structure and evolution of the Early Paleozoic strata in this orogenic belt.The ages of the LA-ICP-MS zircons of syenite and mottled monzogranite samples studied in this work are 441.6±3.7 Ma to 454.9±4.6 Ma. The age of formation is Ordovician. Geochemical analysis shows that the pluton has high-K calc-alkaline characteristics.Aluminum saturation index shows that it is peraluminous granite. The characteristics of trace elements in rocks indicate that they are enriched in large ionic lithophilic elements(LILEs) Rb, Th, U, K, depleted in Ba, Sr;enriched in high field strength elements(HFSEs) La, Ce, Nd, Zr, and depleted in Nb, P, Ti. The total amount of rare earths in the rocks is 38.7×10-6 to 120.23×10-6, and the light rare earths exhibit obvious differences in heavier rare earths, with higher fractionation and weaker negative Eu anomalies.Based on regional geological data, it is believed that the source region of the Ordovician magma in the Geleaobao area is partially melted upper crustal materials, and the formation environment was a back-arc basin. After the subduction of the ancient Asian Ocean to the north, it experienced an island-arc magmatic process cycle, being product of extension stage.

关 键 词：格勒敖包 奥陶纪 侵入岩 地球化学特征 弧后盆地 

分 类 号：P534.42[天文地球—古生物学与地层学] P597.3[天文地球—地质学]