• 责任者：Zhang Cong (State Key Laboratory of Continental Tectonics and Dynamics ; Institute of Geology ; CAGS ; Beijing 100037 ; China) ; Zhang Lifei
• 刊名：Acta Petrologica et Mineralogica
• 出版年：2013
• 卷期：33(6)
• 关键词：片麻岩 ; gneisses ; 铀—钍—铅计时 ; U-Th-Pb dating ; 柴达木盆地 ; Qaidam Basin
• 页码：p.1037-1056
• 图表：6 illus., 3 tables, 60 refs.
• 分类号：0802
• issnNo：ISSN1000-6524
• isbnNo：CN11-1966/P

     The metamorphism and age of UHP eclogites and their country rocks constitute the key to understanding the formation and evolution of the UHP metamorphic terranes.However,because of simple mineral assemblages and lack of P-T sensitive minerals,it is difficult to relate the petrological characteristics with the metamorphic ages of the country rock paragneiss.This paper focused on the petrology and in-situ electronic microprobe monazite U-Th-total Pb dating of three paragneisse samples from Dulan terrane in North Qaidam UHP metamorphic belt.As a result,ages of 433 ± 15.4 Ma （8S01 from Shaliuhe cross-section）,440 ± 11.2 Ma （8S55 from Yematan in North Dulan） and 435 ± 14.7 Ma （8S116 from South Dulan） were obtained respectively.Monazites in paragneiss from Shaliuhe section and South Dulan yielded similar ages,which are different from ages of samples from North Dulan by about 5 Ma.The analyses of the three monazite samples from the Dulan terrane show that they are enriched in LREE and lack of HREE,characterized by positive Eu anomaly.The Eu/ Eu ＊ ratios of monazite have coupling relationship with Ca content in garnet in the matrix.In combination with petrological investigation,P-T calculation and monazite microprobe analysis,the authors hold that the monazite in this study grew or recrystallized under the arnphibolite facies metamorphic conditions during retrogression.The monazite analyses with ages from 440 Ma to 430 Ma in paragneiss from South Dulan are characterized by relatively high Y content.Furthermore,the Y content has an obvious negative correlation with Eu/Eu ＊,suggesting that part of the paragneiss in Dulan terrane had experienced amphibolite facies metamorphism during 440 ～430 Ma.