A comparative discussion of the evidence for biogenic silica in Wufeng-Longmaxi siliceous shale reservoir in the Sichuan basin, China

The siliceous Wufeng-Longmaxi Formation is the main shale gas play in China. It contains a large amount of silica, which has been reported to be of biogenic origin. The previous evidences for a biogenic origin include the presence of siliceous skeletal debris resembling organisms, such as sponge spicules, various parameters, such as the ratios of Al/(Al + Fe + Mn) and Si/(Si + Fe + Al + Ca), and a number of different correlations, such as a...