Research on the smectite-illite reaction: Past history, current status, and future trends
Hailiang Dong, Department of Geology, Miami University, 114 Shideler Hall, Oxford, OH 45056, Fax: 513-529-1542, dongh@muohio.edu, Phone: 513-529-2517

The smectite to illite (S-I) reaction is one of the most important reactions in clay-rich rocks during sedimentary diagenesis, as the degree of the reaction is linked to the maturation, migration and trapping of hydrocarbons, rock cementation, and water chemistry. Early studies largely depended on X-ray diffraction. Application of transmission electron microcopy since late 1980's has contributed much to our understanding of the crystal chemical relations and the reaction mechanisms. At the same time, microbes were recognized as important agents mediating the iron redox cycle in smectites. Recent evidence (after 2000's) demonstrated that iron-reducing microbes can accomplish the S-I reaction at much lower temperature and pressure than those in absence of microbes, with important implications for refining the S-I reaction kinetic models. Currently technologies are being developed to use microbially reduced smectites/illites to remediate environmental contaminants. Research on this important reaction will likely continue with important theoretical and practical implications.