The oldest basement rock in the Yangtze Craton revealed by zircon U-Pb age and Hf isotope composition
Here we report an integrated study of zircon U-Pb age and Hf isotope composition for a gneiss sample from the Kongling terrain in the Yangtze Craton. CL imaging reveals that most zircons are magmatic, and a few of them have thin metamorphic rims. The magmatic zircons gave a weighted mean U-Pb age of 3218±13 Ma, indicating the gneiss is the oldest basement rock in the Yangtze Craton found to date. They have ɛ Hf(t) value of −2.33±0.51, and two-stage Hf model age of 3679±49 Ma, indicating that the gneiss was derived from partial melting of >3.6 Ga crustal rock. The metamorphic rims yielded an age of 2732±16 Ma, implying that the metamorphic event occurred in the Neoarchean era, which may be also a major tectono-thermal event in the Yangtze Craton.
KeywordsKongling zircon U-Pb age Hf isotope composition oldest basement rock
Unable to display preview. Download preview PDF.
- 8.Gao S, Ling W L, Qiu Y M. Contrasting geochemical and Sm-Nd isotopic compositions of Archean metasediments from the Kongling high-grade terrane of the Yangtze craton: Evidence for cratonic evolution and redistribution of REE during crustal anatomies. Geochim Cosmichim Acta, 1999, 63: 2071–2088CrossRefGoogle Scholar
- 9.Yuan H H, Zhang Z L, Liu W, et al. Dating of zircons by evaporation method and its application (in Chinese). Mineral Petrol, 1991, 11: 72–79Google Scholar
- 10.Ma G G, Li H Q, Zhang Z C. An investigation of the age limits of the Sinian System in South China (in Chinese with English abstract). Yichang Inst Geol Min Resour Bull, 1984, 8: 1–29Google Scholar
- 13.Ludwig K R. Users Manual for Isoplot/Ex (rev. 2.49): A Geochronological Toolkit for Microsoft Excel. Berkeley Geochronology Center, Special Publication, 2001. 1: 55Google Scholar
- 19.Griffin W L, Wang X, Jackson S E, et al. Zircon chemistry and magma mixing, SE China: in-situ analysis of Hf isotopes. Tonglu and Pingtan igneous complexes. Lithos, 2002, 61: 237–269Google Scholar
- 24.Ling W L, Gao S, Zheng H F, et al. Sm-Nd isotopic dating of Kongling terrain. Chin Sci Bull, 1998, 1: 86–89Google Scholar