西藏罗布莎群中火山岩夹层LA-ICP-MS锆石U-Pb年龄及其意义  

LA-ICP-MS zircon U-Pb age of the tuffs from the Luobusha conglomerates in southeast Tibet and its implications

作　　者：孔明[1] 江万[2] 刘成东[1] 李晓雄[3] 杨云汉[1] 叶培盛[2] 

机构地区：[1]东华理工大学省部共建核资源与环境国家重点实验室培育基地,江西南昌330013 [2]中国地质科学院地质力学研究所,北京100081 [3]地质过程与矿产资源国家重点实验室中国地质大学地球科学与资源学院,北京100083

出　　处：《地质通报》2015年第2期328-336,共9页Geological Bulletin of China

基　　金：中国地质调查局项目(编号:1212011220937;1212011120182)

摘　　要：针对泽当西郊贡巴日北坡剖面罗布莎群砾岩下部厚约15m的火山岩夹层进行锆石定年,测试结果表明,该火山岩LAICP-MS锆石U-Pb年龄为18.7±0.2Ma,罗布莎群下伏花岗岩LA-ICP-MS锆石U-Pb年龄为29.9±0.4Ma。据此认为,罗布莎群砾岩初始沉积时代约为20Ma前。火山岩的出现表明,中新世布尔迪加尔期罗布莎群发育一期火山活动,结合前人研究认为,沿雅鲁藏布江结合带的狭长范围内自西向东发育一期火山活动,代表雅鲁藏布江缝合带的一次活化,其时空分布特征与冈底斯带中新世钾质—超钾质火山活动具有显著的相似性。The age of the felsic tuff interbedded with the Luobusha conglomerates in western Zetang County is reported for the first time in this paper. LA-ICP-MS zircon U-Pb analysis shows that the tuffs were formed at 18.7 ± 0.2Ma, and hence the time of the initial deposition should be about 20Ma, whereas the LA-ICP-MS zircon U-Pb age of granite underlying the Luobusa conglomer-ates is 29.9±0.4Ma. The existence of the tuff documents a volcanic activity developed at 18.7±0.2Ma. In combination with geochro-nologic data from previous work, the authors hold that volcanic activities were developed all along the Yarlung Zangbo suture zone, meaning the re-activation of the suture zone, which is remarkably similar to the potassic-ultrapotassic volcanism along the Gangdise zone in time and space.

关 键 词：LA-ICP-MS锆石U-PB年龄 火山岩 罗布莎群砾岩 泽当 

分 类 号：P588.14[天文地球—岩石学] P597.3[天文地球—地质学]