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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
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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.
出处 《地质通报》 CAS CSCD 北大核心 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)
关键词 LA-ICP-MS锆石U-PB年龄 火山岩 罗布莎群砾岩 泽当 LA-ICP-MS zircon U-Pb age volcanic rock Luobusha conglomerates Zetang
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