Petrogenesis and dating of the Kangding complex, Sichuan Province

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 Sichuan Province was conducted. One of our conclusions is that a majority of the zircons crystallized between 721 and 773 Ma in a magmatic regime. The complexes contain early to late Paleo-proterozoic relict zircons from ancient continental crust. The oldest age, 2468 Ma, may represent 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.