The Thermal Transformation of Smectite to Illite

  • A. M. Pytte
  • R. C. Reynolds


Mixed-layered illite/smectite minerals composed of 80% illite layers have been identified from different argillaceous rocks that have been subjected to estimated peak temperatures that ranged from 250°C to 70°C, for durations of approximately 10 yr to 300 my. These observations strongly suggest that the reaction progress or extent is controlled by kinetic factors rather than by equilibrium factors. A sixth-order kinetic expression (first-order with respect to the pore-fluid activity ratio K/Na, and fifth-order with respect to the mole fraction of smectite) was successfully applied to the progressive illitization of smectite in the contact metamorphic zone adjacent to an 8.5-m-thick basalt dike that penetrates the upper Pierre Shale near Walsenberg, Colorado. The kinetic expression, together with its preexponential constant and activation energy (33 kcal/mol), provides a fair to good transformation model for a young geothermal sequence, and for burial diagenetic profiles that range in stratigraphic age from approximately a few million to 300 Ma.

The sixth-order model is an empirical device that explains the field evidence, but probably has little or no fundamental physical-chemical significance. The correct kinetic law is likely to be a chain of low-order reactions, each of which has kinetic constants that differ from the others.


Clay Mineral Gulf Coast Reaction Profile Contact Metamorphism Burial Diagenesis 
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  1. Altaner, S.P., Hower, J., Whitney, G., and Aronson, J.L. 1984. Model for K-bentonite formation: Evidence from zoned K-bentonites in the disturbed belt, Montana. Geology 12:412–415.CrossRefGoogle Scholar
  2. Aronson, J.L., and Hower, J. 1976. Mechanism of burial metamorphism of argillaceous sediment: 2. Radiogenic argon evidence. Geological Society of America Bulletin 87:738–744.CrossRefGoogle Scholar
  3. Aronson, J.L., and Lee, M. 1986. K/Ar systematics of bentonite and shale in a contact metamorphic zone, Cerrillos, New Mexico. Clays and Clay Minerals 34:483–487.CrossRefGoogle Scholar
  4. Boles, J.R., and.Franks, S.G. 1979. Clay diagenesis in Wilcox sandstones of southwest Texas: Implications of smectite diagenesis on sandstone cementation. Journal of Sedimentary Petrology 49:55–70.Google Scholar
  5. Bruce, C.H. 1984 Smectite dehydration—its relation to structural development and hydrocarbon accumulation in northern Gulf of Mexico Basin. American Association of Petroleum Geologists Bulletin 68:673–683.Google Scholar
  6. Burst, J.F., Jr. 1969. Diagenesis of Gulf Coast clayey sediments and its possible relation to petroleum migration. American Association of Petroleum Geologists Bulletin 53:73–93.Google Scholar
  7. Eberl, D.D. 1978a. Reaction series for dioctahedral smectites. Clays and Clay Minerals 26:327–340.CrossRefGoogle Scholar
  8. Eberl, D.D. 1978b. The reaction of montmorillonite to mixed-layered clay: The effect of interlayer alkali and alkaline earth cations. Geochimica et Cosmochimica Acta 42:1–7.CrossRefGoogle Scholar
  9. Eberl, D.D., and Hower, J. 1976. Kinetics of illite formation. Geological Society of America Bulletin 87: 1326–1330.CrossRefGoogle Scholar
  10. Hoffman, J., and Hower, J. 1979. Clay mineral assemblages as low grade metamorphic geothermometers: Application to the thrust faulted disturbed belt of Montana, U.S.A. In: Scholle, P.A., and Schluger, P.R. (eds.): Aspects of Diagenesis. Society of Economic Paleontologists and Mineralogists Special Publication 26, pp. 55–79.Google Scholar
  11. Hower, J., Eslinger, E., Hower, M.E., and Perry, E.A. 1976. Mechanism of burial metamorphism of argillaceous sediment: 1. Mineralogical and chemical evidence. Geological Society of America Bulletin 87: 725–737.CrossRefGoogle Scholar
  12. Huff, W.D., and Turkmenoglu, A.G. 1981. Chemical characteristics and origin of Ordovician K-Bentonites along the Cincinnati Arch. Clays and Clay Minerals 29:113–123.CrossRefGoogle Scholar
  13. Jaeger, J.C., 1964. Thermal effects of intrusions. Reviews of Geophysics 2:443–466.CrossRefGoogle Scholar
  14. Jennings, S., and Thompson, G.R. 1986. Diagenesis of Plio-Pleistocene sediments of the Colorado River delta, southern California. Journal of Sedimentary Petrology 56:89–98.Google Scholar
  15. Johnsson, M.J. 1984. The thermal and burial history of south-central New York: Evidence from vitrinite reflectance, clay mineral diagenesis, and fission track dating of apatite and zircon. M.A. thesis, Dartmouth College, Hanover, NH, 155 pp.Google Scholar
  16. Kramer, M.S. 1981 Contact metamorphism of the Mancos Shale associated with the intrusion at Cerrillos, New Mexico. M.A. thesis, Dartmouth College, Hanover, NH, 102 pp.Google Scholar
  17. Lippmann, F. 1982. The thermodynamic status of clay minerals. In: van Olphen, H., and Veniale, F. (eds.): International Clay Conference 1981. Amsterdam, Elsevier Scientific Publishing Co., pp. 475–485.Google Scholar
  18. Lynch, L., and Reynolds, R.C., 1984. The stoichiometry of the illite-smectite reaction (abst.). Twenty-First Annual Meeting of the Clay Minerals Society, Baton Rouge, LA, p. 84.Google Scholar
  19. Nadeau, PH., and Reynolds, R.C., 1981. Burial and contact metamorphism in the Mancos shale. Clays and Clay Minerals 29:249–259.CrossRefGoogle Scholar
  20. Perry, E.A., and Hower, J. 1970. Burial diagenesis in Gulf Coast peletic sediments. Clays and Clay Minerals 18:165–177.CrossRefGoogle Scholar
  21. Perry, E.A., and Hower, J. 1972. Late-stage dehydration in deeply buried peletic sediments. American Association of Petroleum Geologists Bulletin 56:2013–2021.Google Scholar
  22. Pytte, A.M. 1982. The kinetics of the smectite to illite reaction in contact metamorphic shales. M.A. thesis, Dartmouth College, Hanover, NH, 78 pp.Google Scholar
  23. Reynolds, R.C., 1980. Interstratified clay minerals. In: Brindley, G.W., and Brown, G., (eds.): Crystal Structures of the Clay Minerals and Their X-Ray Identification. London, Mineralogical Society, 495 pp.Google Scholar
  24. Reynolds, R.C., 1981. Mixed-layered illite-smectite in a contact metamorphic environment (abst.). Eighteenth Annual Meeting of the Clay Minerals Society, University of Illinois at Urbana-Champaign, Urbana, IL, p. 5.Google Scholar
  25. Reynolds, R.C., and Hower, J. 1970. The nature of interlayering in mixed layer illite/montmorillonite. Clays and Clay Minerals 18:25–36.CrossRefGoogle Scholar
  26. Roberson, H.E., and Lahann, R.W. 1981. Smectite to illite conversion rates: Effect of solution chemistry. Clays and Clay Minerals 29:129–135.CrossRefGoogle Scholar
  27. Robie, R.A., Hemingway, B.S., and Fisher, J.R. 1978. Thermodynamic properties of minerals and related substances at 298.15 K and 1 bar (105 Pascals) pressure and at higher temperatures. U.S. Geological Survey Bulletin 1452, 456 pp.Google Scholar
  28. Środoń, J., and Eberl, D.D. 1984. Illite. In: Bailey, S.W. (ed.): Micas: Reviews in Mineralogy: Vol. 13. Reno, NV, Mineralogical Society of America, 584 pp.Google Scholar
  29. Tyler, L.D., Cuderman, J.F., Kruhansl, J.L., and Lappin, A.R. 1978. Near-surface heater experiments in argillaceous rocks. In: Seminar on In Situ Heating Experiments in Geologic Formations, Ludvika, Stripa, Sweden. Brussels, Belgium, Organization of Economic Cooperation and Development, pp. 31–43.Google Scholar
  30. Weaver, C.E. 1953. Mineralogy and petrology of some Ordovician K-bentonites and related limestones. Geological Society of America Bulletin 64:921–964.CrossRefGoogle Scholar

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© Springer-Verlag New York Inc. 1989

Authors and Affiliations

  • A. M. Pytte
  • R. C. Reynolds

There are no affiliations available

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