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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.
U-Pb zircon dating by LA-ICP-MS and SHRIMP 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 and Paleoproterozoic age of 1844 ± 13 Ma, Neoarchean age of 2541 ± 54 Ma andmiddle Archean age of 3123 ± 4.4 Ma. The 97--158 Ma and 228 ± 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 that that Mesozoic granu-lite-facies metamorphism was induced by heating from the basaltic 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 important crust evolutionary events in the North China craton, and imply preservation of Precambrian lower crust in thepresen t-day lower crust.