内蒙古西部阿拉善地区哈里努登花岗岩LA-ICP-MS锆石U-Pb年龄和地球化学特征  

LA-ICP-MS zircon U-Pb age and geochemistry of the Early Permian Halinudeng granite in northern Alxa area,western Inner Mongolia

作　　者：史兴俊[1,2] 童英[2] 王涛[2] 张建军[1,2] 张招崇[1] 张磊[2] 郭磊[2] 曾涛[2] 耿建珍[3] 

机构地区：[1]中国地质大学,北京100083 [2]中国地质科学院地质研究所,北京100037 [3]中国地质调查局天津地质矿产研究所,天津300170

出　　处：《地质通报》2012年第5期662-670,共9页Geological Bulletin of China

基　　金：中国地质调查局项目<中国和亚洲不同造山带花岗岩>(编号:1212010611803);<全国地质志>(编号:1212010811033);国家自然科学基金项目<阿尔泰南缘晚古生代两期碱性花岗岩时空分布;成因特点及构造意义>(批准号:40702010)

摘　　要：哈里努登岩体位于阿拉善地块北缘,主要由花岗闪长岩、黑云母二长花岗岩组成。锆石LA-ICP-MS U-Pb测年显示其形成时代为284.0Ma±1.8Ma,并非以往认为的志留纪。岩石SiO2含量为67%~72%,CaO为2.2%~4.4%,Na2O为3.7%~4.3%,K2O为2.1%~2.9%,具有较高的全碱含量,属钙碱性—高钾钙碱性系列,Al2O3含量为14.5%~17.2%,为准铝—弱过铝质（A/CNK=0.90~1.07）,总体显示出I型花岗岩的特征。稀土元素总量较低（35.2×10-6~130.6×10-6）,轻稀土元素相对富集,Eu呈正异常（δEu=1.04~1.90）。在原始地幔标准化图解中,大离子亲石元素（K、Rb、Ba、Sr）富集,亏损高场强元素（Ta、Nb、P、Yb、Y等）,显示出弧花岗岩的特征。结合区域背景分析,阿拉善北缘在早二叠世时可能还存在与弧物质有关的岩浆活动。The Halinudeng pluton is located in the northern margin of Alxa area.LA-ICP-MS U-Pb dating of zircons from the pluton yields an age of 284.0±1.8 Ma,indicating that the formation of this pluton is Permian instead of Silurian as previous considered.The main rock types of the pluton include biotite-plagioclase granites and biotite monzogranites,with high SiO2（67%-72%）,CaO（2.2%-4.4%） and Al2O3（14.5%-17.2%）.Geochemical characteristics indicate that they are metaluminous-weakly peraluminous（A/CNK=0.90-1.07） and calc-alkaline to high-K calc-alkaline rocks（Na2O=3.7%-4.3%,K2O=2.1%-2.9%）,assuming characteristics of I-type granite.The rocks have lower REE contents（35.2×10-6-130.6×10-6） with relative enrichment of LREE and positive Eu anomaly（δEu=1.04-1.90）.The primitive mantle normalized trace element patterns are characterized by the enrichment of the LILE（K,Rb,Ba,Sr） and depletion of the HFSE（Ta,Nb,P,Yb,Y）,showing the features of arc granites.It is considered that the northern margin of Alxa might still have had some arc-related magmatic activities during the Early Permian period.

关 键 词：阿拉善地区 二叠纪 花岗岩 锆石U-PB年龄 弧 

分 类 号：P597.3[天文地球—地球化学] P595[天文地球—地质学]