Experimental and Field Constraints on the Role of Silica–Organic Complexation and Silica–Microbial Interactions during Sediment Diagenesis

Summary

This paper reviews the results of experiments and field studies that examine the role of silica–organic interactions that may influence Si transport during sediment diagenesis. Three types of influences are reviewed: (i) aqueous silica–organic complexation; (ii) mineral surface silica–organic complexation; and (iii) microbial influences. The available evidence suggests that aqueous silica–organic complexation does not exert a significant effect on Simobilities in the deep subsurface. Mineral surface silica–organic complexation can lead to enhanced quartz dissolution rates, but not at the temperatures, or for the organic acid anions, currently known to exist in sedimentary basin formation waters. The role of microorganisms on Si transport during diagenesis is just beginning to be investigated, although it is possible that microbial influences such as enhanced quartz dissolution due to microbial exudates, or bacterial-induced silicate mineral precipitation, can significantly affect Si mobilities. Although microorganisms have been found at extreme depths within sedimentary basins, more research must be conducted to determine the importance of microbial processes during deep sedimentary diagenesis.