Development of a mid-Neoproterozoic arched rift in eastern South China as a response to the Rodinia breakup

Abstract

The initial time (before or after ∼ 820 Ma) and geodynamic mechanism (bottom-up rising mantle plume or top-down deep subduction) of Rodinia breakup remain unresolved. This issue has impacted our current understanding of the tectonic evolution of South China. Some scholars believe that separation of the South China Craton (SCC) from the Rodinia supercontinent and contemporary SCC rifting began at ca. 860 Ma and was induced by a subduction-related extension event. In addition, other researchers consider that the SCC rifting occurred after ca. 820 Ma. We show that renewed Rodinia breakup within or along the margin of South China occurred ca. 820–740 Ma, which is supported by early studies and our newly obtained U–Pb zircon ages of 755.4 ± 1.0 and 801.6 ± 5.2 Ma from basalts and mafic intrusive bodies in an arched (arc-shaped) belt. Major elemental variations and calculated datasets for the rift-related igneous rocks suggest a mantle plume origin for the dated rocks, which indicates that the SCC rifting was driven by a rising mantle plume and formed several rifts. This arched belt, including < 820 Ma sedimentary and igneous rocks within it, may well have been the eastern part of the original Nanhua Rift, i.e., the prototype of the Nanhua Rift should be a “T” shape. Owing to a barren magmatic area at the “T” junction, the Nanhua Rift must have split into the Nanhua Rift and arched rift. We suggest that the first stage of rifting event during 860–825 Ma may occurred in the interior Yangtze or Cathaysia Block and was associated with a subduction-related extension event.