新疆西昆仑黑石北湖地区巴颜喀拉山群安山质沉凝灰岩LA-ICP-MS锆石U-Pb年龄

对新疆西昆仑黑石北湖地区巴颜喀拉山群碎屑岩系安山质沉凝灰岩夹层的锆石进行LA-ICP-MS U-Pb同位素年龄测定。研究结果表明,在去掉出现明显U亏损的4个点后,剩下的10个测点206Pb/238U年龄加权平均值为252.9±9.1 Ma,代表安山质沉凝灰岩岩浆物质的形成时间,时代为晚二叠世—早三叠世。但沉凝灰岩的形成时间一般晚于喷发时间,因此该火山岩夹层的形成时代为早三叠世。通过对该套地层时代的讨论,为本区进一步研究巴颜喀拉山群的物质组成及形成时代提供了新的证据。

LA-ICP-MS zircon U-Pb ages of andesic tuffite from Bayan Har Group,Heishi North Lake area,west Kunlun,Xinjiang

Using LA-ICP-MS method,the authors conducted zircon U-Pb isotopic dating of andesite tuffite of Bayan Har Group in the Heishi North Lake area,west Kunlun,Xinjiang.The results show that,after removing the 4 points with obvious U depletion,the weighted 206Pb/238U age of the remaining 10 measurement points is 252.9±9.1 Ma,which represents the formation time of the magmatic material of andesic tuffite,and the age suggests Late Permian-Early Triassic period.However,the formation of the andesic tuffite was usually later than the eruption,so the volcanic interlayer was formed in the Early Triassic.The discussion on andesic tuffite provides new evidence for the further study of the material composition and formation age of Bayan Har Group in this area.