South China in Rodinia: Constrains from the Neoproterozoic Suixian volcano-sedimentary group of the South Qinling Belt

Abstract

The South Qinling Belt, incorporating the northern margin of the Yangtze Block, South China Craton, records a series of Neoproterozoic to Triassic cycles of ocean opening and closing. The Neoproterozoic Suixian Group provides a record of breakup of the Rodinia supercontinent. New zircon U-Pb ages, Hf isotopes and whole-rock elemental data from the group constrain the broader tectonic evolution of the South Qinling Belt and the position of South China within Rodinia. The Suixian Group comprises sandstone and siltstone associated with minor interlayered volcanic rocks. Detrital zircons show three U-Pb age peaks at ∼2450 Ma, ∼1990 Ma and ∼750 Ma, with a minimum age of ∼700 Ma. Their εHf(t) values range from –22.5 to +11.1. Zircon U-Pb and Hf isotopic data are similar to the age range and Hf isotopic character of magmatic zircons from the Precambrian igneous rocks in the South Qinling Belt, which in combination with the euhedral to subhedral apperance of the detrital zircons, suggests local derivation from rock units within the belt. The sedimentary rocks from the Suixian Group have high La/Sc (0.91–7.28), Th/Sc (0.56–2.16) and low Cr/Th ratios (0.94–5.28), implying derivation from felsic volcanic rocks. Their elemental contents and ratios are similar to those accumulating in a continental arc environment. Similarly, the detrital zircons from the late Neoproterozoic sedimentary rocks along the margins of the Yangtze Block show a dominant U-Pb age peak of 770 Ma to 710 Ma, suggesting significant input from an approximately syn-depositional magmatic source. The Neoproterozoic detrital zircons show similar age distributions and εHf(t) values to those of the Neoproterozoic igneous rocks around of the Yangtze Block, suggesting that these sedimentary rocks were sourced from a magmatic arc. The Yangtze Block and northern India preserve similar Neoproterozoic sedimentary successions and detrital age populations indicating that they were closely connected and located along either the margin of Rodinia or on a plate isolated from Rodinia.