U–Pb and Hf isotope analyses of detrital zircons from Late Paleozoic sediments: Insights into interactions of the North China Craton with surrounding plates

Abstract

U–Pb dating and Hf isotope analyses were performed on detrital zircons from the Upper Permian sandstones in the Ordos and Jiyuan basins, with aims of defining the sediment provenance, and by inference, to determine the influence of the surrounding plates on the evolution of the North China Craton (NCC). Detrital Zircons from these two basins fall into three major groups based on their U–Pb ages: Phanerozoic, Paleoproterozoic, and Neoarchean. The youngest grain from every sample is only slightly younger than the real depositional age of strata. The Phanerozoic zircons from the Jiyuan basin (244–390 Ma) show ε Hf ( t) ranging from −30.3 to −1.3, suggesting a provenance from the Inner Mongolia Paleo-uplift (245–376 Ma, ε Hf ( t) = −18.9 to −1.7). A bi-modal distribution of ages and ε Hf ( t) is noted for detrital zircons from the Ordos basin; one resembles that of the Jiyuan basin, the other is characterized by Early Paleozoic ages and relatively high ε Hf ( t) values (−10.9 to 7.7). A hybrid source is thus inferred for the Ordos sediments; the Northern Qinling Orogen (428–478 Ma, ε Hf ( t) = −10.9–7.7) must have served as a source in addition to the Inner Mongolia Paleo-uplift source. This interpretation is consistent with the fact that the Northern Qinling Orogen was an active margin during the Early Paleozoic and suggests that the western part of the Northern Qinling Orogen was elevated relative to the center of the craton during the Late Paleozoic. It is likely that the Early Paleozoic arc-trench in the northern part of the Dabie Orogen was under-thrusted below the NCC due to the subduction of the Yangtze plate during the Triassic. The Inner Mongolia Paleo-uplift was strongly uplifted by subduction of the Paleo-Asian Ocean Plate underneath the northern NCC and functioned as a sediment source for the inner craton during the Late Paleozoic. These results reveal a heterogeneous pattern of destruction of the North China Craton, with its northern margin starting to be activated no later than Late Paleozoic.