STRUCTURE AND KINETICS OF AUTHIGENIC CLAY FORMATION IN TERRESTRIAL AND MARINE ENVIRONMENTS

The structure and chemical composition of clay minerals play an important role in controlling many Earth surface physical and chemical processes. Accumulating research findings are pointing to the important role of clay minerals in trapping trace elements, organic carbon, inorganic and organic contaminants, and nutrients in soils and marine sediments irrespective of the weak clay mineral binding efficiency of many of these species, suggesting the role of clay minerals in kinetically slow reactions involving adsorption and structural incorporation. Yet the nucleation of clay minerals, and their structural evolution in lower temperature environments is widely debated. Information on the genesis of clay minerals in low-temperature environments is vital in the prediction of elemental cycles.

Many observations from both laboratory and field studies suggest that clay minerals can form from the structural modification and weathering of high temperature layered silicates, such as micas, epitaxial growth on layered silicates, and from the precipitation and alteration of Al-silicate gels. Although the kinetics are slow, the latter is considered as the predominant pathway in soil and marine settings. I present a summary of these observations, our findings on the nucleation and growth of clay minerals, and possible pathways for the formation of clay minerals and their kinetics of formation in low temperature settings.