工作得到国土资源部岩浆作用成矿与找矿重点实验室老师和同学的帮助; 长安大学段丰浩博士在论文写作过程中给予了指导和帮助，审稿专家对本文提出了许多宝贵意见，在此一并致谢！
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Abstract： The geological age of the Jimunai Formation has long been controversial in the Saur Mountain of West Junggar.It is also a volcanic-sedimentary stratum with the highest proportion of volcanic rocks to the total thickness of strata，and thus，it is an effective method to resolve the age divergences of the Jimunai Formation using accurate geological age of the volcanic rocks. LA-ICP-MS dating was used to determine the zircons from the newly discovered rhyolite of the upper Jimunai Formation，which yielded zircon U-Pb age of 304.1±2.5 Ma （n=15，MSWD=1.07），corresponding to the end of the Late Carboniferous. In view of predecessors′ fossil information，we suggest that the formation age of Jimunai Formation is Bashkirian to Kasimovian of Late Carboniferous.Isotopic dating of rhyolite accurately constrained the minimum age of the Jimunai Formation，and provided new chronological evidence for the establishment of regional stratigraphic framework and stratigraphic correlation.
Key words： West Junggar;Jimunai Formation;LA-ICP-MS zircon U-Pb dating of rhyolite; Late Carboniferous
