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内蒙古西乌珠穆沁旗晚二叠世花岗岩的锆石U- Pb年龄、地球化学特征及其构造意义
投稿时间:2018-06-13  修订日期:2018-10-13  点此下载全文
引用本文:范玉须,李廷栋,肖庆辉,程杨,李岩,郭灵俊,罗鹏跃.2019.内蒙古西乌珠穆沁旗晚二叠世花岗岩的锆石U- Pb年龄、地球化学特征及其构造意义[J].地质论评,65(1):248-266,[DOI]:.
FAN Yuxu,LI Tingdong,XIAO Qinghui,CHENG Yang,LI Yan,GUO Lingjun,LUO Pengyue.2019.Zircon U- Pb Ages, Geochemical Characteristics of Late Permian Granite in West Ujimqin Banner, Inner Mongolia, and Tectonic Significance[J].Geological Review,65(1):248-266.
DOI:10.16509/j.georeview.2019.01.017
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作者单位E-mail
范玉须 1) 中国地质科学院地质研究所北京100037 562442919@qq.com 
李廷栋 1) 中国地质科学院地质研究所北京100083 qinghuixiao@126.com 
肖庆辉 1) 中国地质科学院地质研究所北京100083  
程杨 2) 中国冶金地质总局矿产资源研究院北京101300  
李岩 2) 中国冶金地质总局矿产资源研究院北京101300  
郭灵俊 3) 内蒙古自治区地质调查院呼和浩特010020  
罗鹏跃 3) 内蒙古自治区地质调查院呼和浩特010020  
基金项目:注: 本文为内蒙古自治区地质矿产勘查基金资助项目(编号:2017 YS01)和中国地质调查项目(编号:DD20160345)的成果。
中文摘要:内容提要: 西乌珠穆沁旗西南部色尔崩岩体和努和亭沙拉岩体的锆石U- Pb年龄为255.3±1.4Ma和254.4±3.4Ma,是晚二叠世晚期岩浆活动的产物。岩石地球化学分析发现,花岗岩属于钙碱系列,富钠贫钾,具有高Sr(Sr≥741×10-6)低Y、Yb及高Sr/Y的特点,轻重稀土分异显著(10.25<(La/Yb)N<22.51),弱的正Eu异常(1.06<δEu<1.46),富集大离子亲石元素(LILE),亏损高场强元素(HFSE),与典型的高锶低钇中酸性岩(adakite,亦有人译为埃达克岩)地球化学特征相似。岩浆锆石具有正的εHf(t)值(+8.1~+13.3)和年轻的二阶段模式年龄(T2DM约为430~760Ma),高Mg#(55~59),表明岩浆熔体与地幔橄榄岩发生了相互作用,暗示这种高锶低钇型花岗岩的形成与俯冲板片在深部发生部分熔融有关。结合区域地质资料认为,古亚洲洋在晚二叠世还未完全闭合,研究区内高锶低钇型花岗岩形成于古亚洲洋持续向北俯冲且俯冲洋壳断离并发生部分熔融构造背景下。
中文关键词:晚二叠世  高锶低钇花岗岩  锆石U- Pb定年  古亚洲洋  构造环境
 
Zircon U- Pb Ages, Geochemical Characteristics of Late Permian Granite in West Ujimqin Banner, Inner Mongolia, and Tectonic Significance
NameInstitution
FAN Yuxu1) Institute of Geology, Chinese academy of Geological Sciences,Beijing,100037
LI Tingdong1) Institute of Geology, Chinese academy of Geological Sciences,Beijing,10037
XIAO Qinghui1) Institute of Geology, Chinese academy of Geological Sciences,Beijing,10037
CHENG Yang2) Institute of Mineral Resources, China Metallurgical Geology Administration,Beijing, 101300
LI Yan2) Institute of Mineral Resources, China Metallurgical Geology Administration,Beijing, 101300
GUO Lingjun3) Geological Survey Institute of Inner Mongolia, Hohhot,010020
LUO Pengyue3) Geological Survey Institute of Inner Mongolia, Hohhot,010020
Abstract:Objectives: Adakite is a kind of intermediate—acid rock with unique geochemical characteristics. It can track the oceanic crust subduction and crustal thickening and other related events in geological history, which is of great significance for the inversion of crustal composition and mineralization. According to previous studies, the granites of Seerbeng and Nuhetingshala in West Ujimqin have the characteristics of adakite, but lacked accurate chronology data. The study on the diagenetic age and tectonic background of the adakite granitoids is helpful to understand the tectonic evolution of the paleo- Asian Ocean. Methods: Based on the field work,through the microscope observation,the whole rock chemical analysis, LA- ICP- MS U- Pb zircon dating of the granitiods and the Hf isotopic analysis. Results:The U- Pb isotopic dating of zircon shows that the ages of Seerbeng pluton and Nuhetingshala pluton in West Ujimqin area are 255.3±0.71Ma and 254.4±1.2Ma, which are the products of magmatic activity in the late Permian.By lithology and rock geochemistry analysis found that belong to calc alkalic rock and high potassium calc alkali series, SiO2 content is 65%~73%, Na rich and K- poor, high Sr, low Yb Y and high Sr/Y, wich consistent with the characteristics of typical adakite.The magmatic zircons are positively εHf(t) values (+8.1~+13.3) and young two- stage model ages varied in 430~760Ma. Adakite rock formation is related to partial melting of young subduction plate,and the high Mg# indicates that magmatic melts interact with mantle peridotite. Conclusions: Combined with regional rock assemblages, the paleo Asian Ocean has not yet completely closed in late Permian. During this stage, the subducted oceanic crust broke off and partially melted, which formed the adakite granitoids and hight Mg andesite. The closing time of the paleo Asian ocean should be after the Permian.
keywords:Late Permian  high- Sr low- Yb granitoids (Adakite)  U- Pb age of zircon  tectonic setting  Inner Mongolia
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