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Paleoproterozoic-Archean Basement beneath Southeast Hubei Province: Evidence from U-Pb-Hf Isotopes in Zircons from the Tonggushan Pluton
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摘要


     This paper has reported the integrated study of zircon U-Pb age and Lu-Hf isotope composition in zircons from the Tonggushan pluton, southeast Hubei Province. Tonggushan pluton is composed of quartz diorite porphyry. The 206pb/238U mean age of magmatic zircon is 147k2.6 Ma, indicating that Tonggnshan pluton was formed in the Late Jurassic-Early Cretaceous, which is consistent with the formation time of other plutons in this area. A large number of inherited zircons, formed in 1798-2888 Ma, exist in Tonggushan pluton. The Paleoproterozoic zircons are of magmatic origin and have similar 176Hf/177Hf and 176Lu/177Hf ratios, suggesting that they were probably derived from the same igneous basement rock. The Paleoproterozoic zircons have low Hf-isotope compositions and characteristics of crustal source. Hf model ages of these zircons and the presence of older inherited cores within them suggest that the source of Paleoproterozoic magma was Neoarchaean crust, implying the existence of an unexposed old basement beneath southeast Hubei Province and the whole Yangtze block. These data supply new clue to the study of the Precambrian basement evolution of Yangtze block. The Paleoproterozoic-Archean basement of the Yangtze Block most likely spreads from the Sichuan Basin throughwestern Huebei Province to southeastern Hubei Province.

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