A petrographic and geochemical study of carbonate and silica phases from the Ediacaran Doushantuo Formation in the Three Gorges area of South China: Implications for diagenetic conditions

Those silica phases without evidence of contamination of continental silicate detritus show characteristic REE + Y patterns, with minor light REE depletions, positive La, Eu and Gd anomalies, negative Ce anomalies and slightly super-chondritic Y/Ho ratios, implying that the source of silica may be derived from seawater. Negative Ce anomalies in the silica phases in D2 through D4 subunits indicate that the bottom seawater or early diagenetic porewater was oxic at the time of silica precipitation.