Episodic Precambrian crust growth: Evidence from U–Pb ages and Hf–O isotopes of zircon in the Nanhua Basin, central South China
MetadataShow full item record
We report here the first integrated U–Pb dating and hafnium–oxygen isotope analyses of detrital zircon grains from sedimentary and volcaniclastic rocks in the Neoproterozoic Nanhua Basin, central South China. These data provide vital information on the depositional cycles of the Cryogenian strata and their bearings on the breakup of the Rodinia supercontinent, and the characteristics of Precambrian crustal growth in the South China Block and neighboring continents. Zircon SIMS U–Pb ages indicate that the Qingshuijiang Formation was deposited at 772 ± 5 Ma and the Fanzhao Formation was deposited between 800 and 770 Ma. The onset time of the Sturtian (Jiangkou) glaciation is constrained to be no older than 730 Ma. Together with compilations of all available high precision zircon U–Pb data on tuff beds in the Nanhua Basin, our work demonstrates that the Cryogenian deposition in South China began at about 850 Ma and had three depositional cycles at ca. 850–820 Ma, 820–720 Ma and 720–635 Ma. Hf isotope analyses and U–Pb dating, combined with existing O isotope analyses, of detrital zircon have revealed three striking features for grains with 1.0–0.7 Ga ages: (1) about 22% of total analysed grains have Hf isotope compositions that plot between the new continental crust and depleted mantle growth curves; (2) about 80% of zircon grains have δ18O values below 6.5‰; and (3) 950–700 Ma is the most dominant age group in the total of 1616 concordant detrital zircon ages from the Cryogenian sedimentary rocks. The Early Neoproterozoic (1.0–0.7 Ga) thus appears to have witnessed significant juvenile crustal growth in South China. In addition, zircon analyses of the Cryogenian sedimentary rocks revealed 3.2–2.9 Ga and possibly 2.7–2.4 Ga as two additional episodes of juvenile crust growth in South China and neighboring continents.
Showing items related by title, author, creator and subject.
Integrated in situ U–Pb age and Hf–O analyses of zircon from Suixian Group in northern Yangtze: New insights into the Neoproterozoic low-δ18O magmas in the South China BlockYang, Y.; Wang, Xuan-Ce; Li, Q.; Li, X. (2016)The mid- to late-Neoproterozoic magmatic rocks from the northern margin of the Yangtze Block are major protoliths of high-pressure (HP) and ultrahigh-pressure (UHP) metamorphic rocks in the Dabie–Sulu orogenic belt along ...
Mid-Neoproterozoic angular unconformity in the Yangtze Block revisited: Insights from detrital zircon U-Pb age and Hf-O isotopesYang, C.; Li, X.; Wang, Xuan-Ce; Lan, Z. (2015)Middle Neoproterozoic sedimentary rocks are widespread in the South China Block, especially around the periphery of the Yangtze Block. They are separated into the Sibao and Danzhou groups (and their equivalents) by a ...
U-Pb age and Hf isotope composition of detrital zircons from Neoproterozoic sedimentary units in southern Anhui Province, South China: Implications for the provenance, tectonic evolution and glacial history of the eastern Jiangnan OrogenCui, X.; Zhu, W.; Fitzsimons, Ian; He, J.; Lu, Y.; Wang, X.; Ge, R.; Zheng, B.; Wu, X. (2015)Neoproterozoic sedimentary units at the southeastern margin of the Yangtze Block, South China, record a complex geological history including development of the Jiangnan Orogen during assembly of the Yangtze and Cathaysia ...