延边地区五道沟群变质英安岩的锆石SHRIMP U-Pb年龄及其地质意义  

SHRIMP U-Pb Ages of Zircon and Its Geological Implications from Metamorphic Dacite of the Wudaogou Group in Yanbian Area

作　　者：于介江[1] 门兰静[1] 陈雷[1] 赵俊康[1] 梁树能[1] 陈冬[1] 逄伟[1] 

机构地区：[1]吉林大学地球科学学院,长春130061

出　　处：《吉林大学学报（地球科学版）》2008年第3期363-367,共5页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(40472050;40772052);南京大学内生金属成矿机制国家重点实验室基金(2005-2006;2006-2008)

摘　　要：延边地区五道沟群变质英安岩中的锆石呈自形-半自形晶,具有较高的Th/U比值(0.28～0.81),表明为岩浆成因。定年结果表明,变质英安岩中锆石具有两组年龄。其中,10个测点的206Pb/238U年龄为(265±5)～(291±5)Ma,其加权平均年龄为(274±7)Ma(MSWD=3.4);另一组3颗锆石的206Pb/238U的加权平均年龄为(323±37)Ma(MSWD=3.6)。前者应代表变质英安岩原岩的形成时代,即早二叠世;后者应代表捕获锆石的年龄。结合最新定年结果,可以认为延边地区五道沟群的形成时代为早二叠世,它们与青龙村群一起,共同构成了晚古生代大陆边缘火山-沉积建造。Zircons from the metamorphic dacite of the Wudaogou Group in Yanbian area have euhedral-subhedral shapes and high Th/U ratios （0.28 - 0.81）, implying their magmatic origin. The dating of these zircons indicates that they can be divided into two groups according to their ages. One group, ^206 Pb/^238 U ages of 10 spots ranging from （265±5）Ma to （291±5）Ma, the weighted mean age of （274±7）Ma （MSWD= 3.4）, represents the formation time of the metamorphic dacite （the Early Permian）, the other include three zircon grains, and its weighted mean ^206 Pb/^238 U age of is （323±37）Ma （MSWD = 3.6）, should be interpreted as the captured zircon ages. Combining with the recently dating data, it is suggested that the Wudaogou Group formed in the Early Permian. Together with the Qinglongcun Group, it constitutes a volcanic - sedimentary formation in the Late Paleozoic continental margin.

关 键 词：五道沟群 变质英安岩 锆石U-PB定年 延边地区 

分 类 号：P534[天文地球—古生物学与地层学]