Zircon U-Pb ages of olivine pyroxenite xenolith from Hannuoba: Links between the 97—158 Ma basaltic underplating and granulite-facies metamorphism  

作　　者：LIUYongsheng YUANHonglin GAOShan HUZhaochu WANGXuance LIUXiaoming LINWenli 

机构地区：[1]FacultyofEarthSciences,ChinaUniversityofGeosciences.Wuhan430074.China [2]KeyLaboratoryofContinentalDynamics,DepartmentofGeology.NorthwestUniversity,Xi'an710069.China

出　　处：《Chinese Science Bulletin》2004年第10期1055-1062,共8页

摘　　要：U-Pb zircon dating by LA-ICP-MS andSHRIMP for one olivine pyroxenite yields complex agepopulations including Mesozoic ages of 97-158 Ma and 228 ±8.7 Ma, Early Paleozoic ages of 418—427 Ma, Paleoprotero-zoic age of 1844±13 Ma, Neoarchean age of 2541 ± 54 Ma andmiddle Archean age of 3123 ± 4.4 Ma. The 97—158 Ma and228 ± 8.7 Ma zircons show typical igneous oscillatory zona-tion in CL images, suggesting two episodes of magmaticevents. Overlapping of the 97-158 Ma ages with that ofgranulite xenoliths indicates that the Mesozoic granu-lite-facies metamorphism was induced by heating from thebasaltic underplating at the base of the lower crust. Bothprocesses lasted at least from about 158 to 97 Ma. Ages of 418--427 Ma could be records of the subduction of Mongoliaoceanic crust under the North China craton. Ages of 1.84 Ga, 2.54 Ga and 3.12 Ga correspond to the three importantcrust-mantle evolutionary events in the North China craton,and imply preservation of Precambrian lower crust in thepresent-day lower crust.U-Pb zircon dating by LA-ICP-MS andSHRIMP for one olivine pyroxenite yields complex agepopulations including Mesozoic ages of 97-158 Ma and 228±8.7 Ma, Early Paleozoic ages of 418--427 Ma, Paleoprotero-zoic age of 1844±13 Ma, Neoarchean age of 2541±54 Ma andmiddle Archean age of 3123±4.4 Ma. The 97--158 Ma and228±8.7 Ma zircons show typical igneous oscillatory zona-tion in CL images, suggesting two episodes of magmaticevents. Overlapping of the 97-158 Ma ages with that ofgranulite xenoliths indicates that the Mesozoic granu-lite-facies metamorphism was induced by heating from thebasaltic underplating at the base of the lower crust. Bothprocesses lastcd at least from about 158 to 97 Ma. Ages of 418--427 Ma could be records of the subduction of Mongoliaoceanic crust under the North China craton. Ages of 1.84 Ga,2.54 Ga and 3.12 Ga correspond to the three importantcrust-mantle evolutionary events in the North China craton,and imply preservation of Precambrian lower crust in thepresent-day lower crust.

关 键 词：锆石U-Pb定年 橄榄辉石岩捕虏岩 玄武岩板块 变质作用 

分 类 号：P597[天文地球—地球化学]