延边东部五道沟岩群的单颗粒锆石SHRIMP U-Pb年代学及其地质意义

Single grain zircon SHRIMP U-Pb chronology the geological significance of the Wudaogou rock group,Yanbian

通过对延边地区东部五道沟岩群黑云阳起石片岩的单颗粒锆石SHRIMPU-Pb年龄测定,获得21个单点年龄,其中包括7组谐和年龄和1组不谐和年龄。谐和年龄分别为1347.8Ma、844.8Ma、340.2～313.7Ma(平均值为323±23Ma,N=4,MSWD=0.23,置信度=0.88)、292.9～288.3Ma(平均值=291±25Ma,N=3,MSWD=0.031,置信度=0.86)、279.2～266.2Ma(平均值为279±28Ma,N=4,MSWD=0.031,置信度=0.86)、127.4～124.2Ma(206Pb/208U年龄平均值为126.5±3.7Ma,N=5,MSWD=0.12;置信度=0.97)、116.1～106.3Ma(平均值为115±39Ma,N=2,MSWD=1.2,置信度=0.27),不谐和年龄的下交点年龄为(451±120)Ma、上交点年龄为(1811±400)Ma(MSWD=7.2);这一结果表明:阳起石片岩的原岩主要是来自中元古代、新元古代和早古生代的碎屑物,指示五道沟群的沉积成岩作用发生在石炭世(323±23Ma),变质作用发生在晚二叠世(291±25Ma),之后在279.2～266.2Ma、126.5～106.3Ma先后受两次岩浆用和蚀变作用的改造。

The single grain zircon CL images and the SHRIMP U-Pb zircon dating for the Biotite-actinolite schist of the Wudaogou Group in the east of Yanbian, yield seven sets of concordant ages and one set of discord ages for 21 zircon spots. The concordant ages are 1347.8 Ma, 844.8 Ma, 340.2-313.7 Ma（Mean=323±23Ma,MSWD = 0.23, reliability = 0.88）, 292.9-288.3 Ma（Mean=291±25 Ma,MSWD = 0.031, reliability=0.86）,279.2-266.2 Ma （Mean= 279 ±28 Ma,MSWD = 0.031,reliability=0.86）,127.4-124.2 Ma （Mean =126.5±3.7 Ma,N=5,MSWD =0.12; reliability=0.97）and 116.1-106.3 Ma（Mean= 115 ±39 Ma,N=2,MSWD =1.2, reliability= 0.27）,respectively;and the discord ages show that the lower and upper intercept ages are 451±120 Ma and 1811±400 Ma （MSWD = 7.2）, respectively. The results indicate that the provenance of the biotite-actinolite schist is clastic materials from Mesoproterozoic, Neoproterozoic and early Paleozoic;the sedimentary diagenesis and metamorphism of Wudaogou Group accurred in Carboniferous and lower-Permian. The wudaogou Group has been reworked two times by magmatism and alteration during the periods of279.2-266.2 Ma and 126.5-106.3 Ma.