Hydrothermal origin of elevated iron, manganese and redox-sensitive trace elements in the c. 635 Ma Doushantuo cap carbonate

Major and trace element, including REE, concentrations of the Doushantuo cap carbonate (c. 635 Ma) in South China show enrichment in Fe, Mn and redox-sensitive elements and slightly negative Ce anomalies, indicating anoxic environments during cap carbonate precipitation. High Fe-T/Al ratios but very low concentration of extractable pyrites suggest ferruginous rather than euxinic conditions. The REE + Y patterns of samples show enrichment of heavy REE (HREE), positive Eu anomalies and positive Yanomalies, implying a hydrothermal origin for elevated concentration of Fe, Mn and redox-sensitive elements. The results suggest that ferruginous Ediacaran oceans may have rooted from hydrothermally induced iron accumulation in severely glaciated Cryogenian oceans.