An analysis of major and trace element geochemistry and SHRIMP U-Pb zircon dating of mafic,intermediate,and felsic rocks from the Mianning metamorphic complex of Si-chuan Province was conducted.One of our conclusions ...An analysis of major and trace element geochemistry and SHRIMP U-Pb zircon dating of mafic,intermediate,and felsic rocks from the Mianning metamorphic complex of Si-chuan Province was conducted.One of our conclusions is that a majority of the zircons crystal-lized between 721 and 773 Ma in a magmatic regime.The complexes contain early to late Pa-leo-proterozoic relict zircons from ancient continental crust.The oldest age,2468 Ma,may rep-resent the basement of the Yangtze block.Overgrowth zircon rims and palingenetic zircons have been observed and dated,and are believed to have formed after crystallization,during Paleozoic and Mesozoic metamorphic-anatexis.We also conclude that depletion of Nb,Ta,HREE,in a spider-diagram normalized to primitive mantle and calc-alkaline association,implies that they formed in island-arc or under-plating settings.展开更多
基金the National Natural Science Foundation of China(Grant Nos.40173007 and 40234052)the Key Project of Ministry of Education of China(Grant No.03032).
文摘An analysis of major and trace element geochemistry and SHRIMP U-Pb zircon dating of mafic,intermediate,and felsic rocks from the Mianning metamorphic complex of Si-chuan Province was conducted.One of our conclusions is that a majority of the zircons crystal-lized between 721 and 773 Ma in a magmatic regime.The complexes contain early to late Pa-leo-proterozoic relict zircons from ancient continental crust.The oldest age,2468 Ma,may rep-resent the basement of the Yangtze block.Overgrowth zircon rims and palingenetic zircons have been observed and dated,and are believed to have formed after crystallization,during Paleozoic and Mesozoic metamorphic-anatexis.We also conclude that depletion of Nb,Ta,HREE,in a spider-diagram normalized to primitive mantle and calc-alkaline association,implies that they formed in island-arc or under-plating settings.
