东昆仑南缘布青山构造混杂岩带早古生代白日切特中酸性岩浆活动：来自锆石U-Pb测年及岩石地球化学证据  

Early Paleozoic intermediate-acid magmatic activity in Bairiqiete area along the Buqingshan tectonic melange belt on the southern margin of East Kunlun: Constraints from zircon U-Pb dating and geochemistry

作　　者：刘战庆[1] 裴先治[1] 李瑞保[1] 李佐臣[1] 陈国超[1] 陈有炘[1] 高景民[1] 刘成军[1] 魏方辉[1] 王学良[1] 张刚[1] 

机构地区：[1]长安大学西部矿产资源与地质工程教育部重点实验室,地球科学与资源学院,陕西西安710054

出　　处：《中国地质》2011年第5期1150-1167,共18页Geology in China

基　　金：国家自然科学基金项目(41172186、40972136、40572121);中央高校基本科研业务费专项资金(CHD2009JC053、CHD2009JC046、CHD2009JC070);青海省国土资源厅-中国铝业公司公益性区域地质矿产调查基金项目(中铝基金200801)联合资助

摘　　要：在1∶50000地质填图基础上,运用剖面测制、岩石学、岩石地球化学及LA-ICP-MS锆石U-Pb法测年等方法,对东昆仑南缘布青山构造混杂岩带内的白日切特中酸性岩浆岩岩块进行详细研究。结果表明:白日切特剖面中酸性岩浆岩岩块主要由花岗闪长岩岩块和中酸性火山岩岩块组成,其中花岗闪长岩锆石206Pb/238U加权平均年龄为(441±6)Ma(MSWD=0.76),流纹斑岩锆石206Pb/238U加权平均年龄为(438±3)Ma(MSWD=2.0)。花岗闪长岩为高硅,富铝、钠,准铝质,钠质钙碱性系列;中酸性火山岩为硅饱和,铝质,钙碱性系列。二者稀土元素总量(∑REE)较低,LREE相对富集,HREE相对亏损,REE配分曲线呈LREE分馏明显,HREE分馏不明显右倾特征,花岗闪长岩基本上无铕异常,而中酸性火山岩具有弱的负铕异常,均与岛弧钙碱性系列的特征相似,与洋壳的俯冲消减作用有关,代表了在早志留世东原特提斯洋壳俯冲消减而形成的火山弧产物,为研究东特提斯洋演化进程提供了新证据。Based on 1∶50 000 regional geological mapping on the southern margin of the East Kunlun Mountains and using methods of detailed field section measurement and petrologic analysis as well as LA-ICP-MS zircon U-Pb dating and geochemical investigation,the authors studied the intermediate-acid magmatic rocks in Bairiqiete area of the Buqingshan tectonic melange belt.The results show that the rocks are mainly granodiorite with 206Pb/238U average weighted age of 441±6 Ma（MSWD=0.75）and intermediate-acid volcanic rock such as rhyolite-porphyry with 206Pb/238U average weighted age of 438±3 Ma（MSWD=2.0）.Geochemically,the former is characterized by high content of Si,Al and Na and should belong to the Na-enriched calc-alkali series,whereas the latter is of Si-saturated,aluminous and calc-alkali series.These two kinds of rocks are characterized by low ∑REE content and relatively enriched LREE and depleted HREE,with LREE differentiated more evidently than HREE,and show right-inclination pattern in REE patterns,without or with weak Eu anomalies.All of these features are similar to features of the island-arc calc-alkali series in relation to subduction,representing the volcanic-arc products of the subduction of east proto-Tethys crust in Early Silurian.The results obtained by the authors provide new evidence for the study of the evolution of east proto-Tethys Ocean.

关 键 词：东昆仑南缘 白日切特 构造混杂岩 中酸性火山岩 花岗闪长岩 LA-ICP-MS锆石U-PB测年 岩石地球化学 

分 类 号：P588.11[天文地球—岩石学] P597.3[天文地球—地质学]