东昆仑闹仓坚沟组流纹质凝灰岩锆石U-Pb年龄及其地质意义  

ZIRCON U-Pb AGES FOR RHYOLITIC TUFFS OF THE NAOCANGJIANGOU FORMATION IN THE EAST KULUN OROGENIC BELT AND THEIR IMPLICATION

作　　者：吴芳[1] 张绪教[2] 张永清[3] 张耀玲[1] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]中国地质大学地球科学与资源学院,北京100083 [3]天津地质矿产研究所,天津300170

出　　处：《地质力学学报》2010年第1期44-50,共7页Journal of Geomechanics

基　　金：中国地质调查局地质调查项目(1212010711510)资助

摘　　要：应用激光烧蚀多接收器电感耦合等离子体质谱(LA-MC-ICP MS)方法对东昆仑秀沟盆地闹仓坚沟组火山岩样品进行了锆石U-Pb定年研究。流纹质凝灰岩(DG25-4)中锆石的阴极发光图像具有振荡环带结构,属于典型的岩浆锆石。15个岩浆锆石206Pb/238U表面年龄集中在239～249 Ma之间,206Pb/238U加权平均值为243.5±1.7 Ma,它记录了火山岩的形成年龄,说明该地区闹仓坚沟组形成于中三叠世早期。这一研究还在闹仓坚沟组火山岩中发现了早古生代和元古宇继承锆石,提供了昆南地体可能存在元古宇基底的信息。By using La-Mc-ICPMC method,accurate zircon U-Pb dating has been made for volcanic rock samples from the Naocangjiangou Formation in the Xiugou basin of the East Kunlun orogenic belt.The zircons from the rhyolitic tuff（sample DG25-4） showed oscillatory girdles in its cathodeluminescence image,indicating a typically magmatic origin.The 206Pb /238 U surface ages of 15 magmatic zircons are concentrated in the range of 239-249 Ma,averaging 243.5 ± 1.7 Ma,which records the forming age of those volcanic rocks,that is,the Naocangjiangou Formation was formed in the early Middle Triassic.Early Paleozoic and Proterozoic zircons were also found in volcanic rocks of the formation,suggesting the possible presence of Proterozoic basement in the Kunlun southern terrain.

关 键 词：闹仓坚沟组 凝灰岩 U-PB年龄 中三叠世 东昆仑造山带 

分 类 号：P597[天文地球—地球化学]