Crustal Growth of the Eastern North China Craton and Sulu Orogen as Revealed by U-Pb Dating and Hf Isotopes of Detrital Zircons from Modern Rivers

Detrial zircon from clastic sediment or sands of modern rivers is an ideal sample for studying the growth and evolution of the continental crust. In order to reveal the crustal growth of eastern North China craton and Sulu orogen, 396 concordant detrital zircons in three sand samples from the Daqing River, Chaobai River, Liao River, Dagu River and Jiaolai River in eastern North China were measured for U-Pb age and Hf isotopic compositions by excimer laser-ablation ICP-MS and MC-ICP-MS, respectively. The Daqing River, Chaobai River and Liao River are characterized by two age peaks of 2.4-2.5 Ga and 1.8-1.9 Ga, which indicate contributions from the eastern North China craton. Some 100-500 Ma zircons from the Liao River with positive ε_Hf(t) values and young Hf model ages, suggesting Phanerozoic crustal growth. In contrast, U-Pb ages of the Dagu River and Jiaolai River, which run through the Sulu orogen, are more complicated and characterized by age groups of 2.4-2.5 Ga, 1.8-1.9 Ga and 700-800 Ma, implying a mixed provenance of eastern North China craton and Yangtze craton. The Lu-Hf isotope compositions of the Daqing River, Chaobai River and Liao River demonstrate the dominant growth at 2.4-3.0 Ga, with a peak at 2.6-2.7 Ga and minor growth during 1.3-2.3 Ga. However, there is insignificant crustal growth during other periods. In addition, 80% of the existing crust in eastern North China craton was produced before Paleoproterozoic and reworking of preexisting continental crust became dominant since then. Meanwhile, a Paleozoic (300-500 Ma) crustal growth characterizes zircon Hf isotopes of the Dagu River of the Sulu orogen.