Paleoproterozoic lower crust beneath Nushan in Anhui Province Evidence from zircon SHRIMP U-Pb dating on granulite xenoliths in Cenozoic alkali basalt
Abstract Zircon SHRIMP U-Pb dating was carried out for an intermediate granulite xenolith in Cenozoic alkali basalt from Nushan. The results suggest that the lower crust beneath Nushan may have formed at about 2400—2200 Ma,and have been subjected to granulite-facies metamorphism at 1915±27 Ma. The old age of the Nushan lower crust is consistent with the geochemical similarities between Nushan granulite xenoliths and Archean-Paleoproterozoic granulite terrains in the North China craton, but it is not distinguishable from high-grade metamorphic rocks in the Yangtze craton where such old ages were also reported.Significant Pb-loss occurs in the Nushan zircons, implying important influence of widespread Mesozoic to Cenozoic underplating in East China on the lower crust beneath Nushan.
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