Microbial Silicon Cycling Promoted Shallow-Sea Chert Deposition in Mesoproterozoic Ocean
Shi Qing
Shi Xiaoying
Jiang Ganqing
Tang Dongjie
Wang Xinqiang
Abstract：To reveal the silicon cycling and potential mechanism of chert deposition in Mesoproterozoic shallow seas,an integrated study of sedimentology,mineralogy,geobiology and geochemistry was conducted on the Wumishan cherts(～1.48 Ga)using multiple techniques.The results show that the cherts are predominated by microquartz(～90%)in composition,with some silica-replaced carbonate(～5%)and minor pyrite(～1%)grains,indicating that the cherts largely originated from primary silica precipitation.High Ge/Si molar ratios(～8.83 μmol/mol)and positive Eu anomalies(～1.41)in the cherts suggest silica largely deriving from seawater(～94%),with a small contribution of thermally derived Si(～6%).Diverse microbial components(e.g.,microbial filaments,EPS(extracellular polymeric substances)relics,mat fragments)and picocyanobacterian fossils were closely associated with organominerals,suggesting that microbial activities played important roles in silica precipitation.The Si liberated from degraded EPS and organo-Si complexes locally increased the dissolved Si concentrations and changed the chemical conditions in shallow substrate and pore-waters,promoting silica precipitation.The flourishing picocyanobacteria and certain prokaryotes that can accumulate silica in their cells or EPS may have changed the Si-cycling in Mesoproterozoic ocean,and the biogenic silica released from the microbial biomass may have promoted the silica precipitation in the Mesoproterozoic shallow-sea environments.
Keywords：Mesoproterozoic marine silicon cyclebiogenic silicamicrobial silicificationseawater dissolved silica concentrationsNorth China Platformsedimentologymineralogy
Publication Date：2025-03-14
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：23( 1082-1104 )