Skip to main content Accessibility help

Fluid composition, mineralogy and morphological changes associated with the smectite-to-illite reaction: an experimental investigation of the effect of organic acid anions

  • J. S. Small (a1)


The smectite-to-illite reaction (illitization) was examined in a dilute suspension of Wyoming bentonite in the presence of oxalate and acetate. Experiments were performed using fluidsampling apparatus at 200°C, 50 MPa, in which progressive changes in both clay mineralogy and fluid composition were monitored. The presence of K-oxalate and K-acetate under neutral-alkaline conditions produced significant reaction of smectite to either R1 or R2 ordered illite-smectite with 60–70% illite layers. Experiments at the same temperature with KCl, or oxalic acid plus KCl, produced no reaction. Fluid chemistry showed that K-oxalate and K-acetate resulted in the establishment of aK+/aH+ conditions within the muscovite stability field, favouring the formation of illite. The extent of dissolution and precipitation indicated by fluid data is insufficient to account for the amount of illitization evident in the mineralogy. This implies that a localized dissolution-precipitation process occurs, perhaps on the scale of a single clay particle. These experiments highlight the importance of pH as a control over illitization and show that organic anions can buffer fluid composition into the optimum aK+/aH+ condition for illitization. These findings are highly significant for the smectite-to-illite reaction occurring in organic bearing sediments where organic acid anions are generated during kerogen maturation.



Hide All
Ahn, J.H. & Peacor, D.R. (1986) Transmission and analytical electron microscopy of the smectite-to-illite transition. Clays Clay Miner. 34, 165179.
Aja, S.U., Rosenberg, P.E. & Kirrrick, J.A. (1991) lllite equilibria in solutions: I. Phase relationships in the system K2O-Al2O3-SiO2-H2O between 25 and 250°C. Geochim. Cosmochim. Acta 55, 13531364.
Cliff, G. & Lorimer, G.W. (1975) The quantitative analysis of thin specimens. J. Mierosc. 103, 203207.
Crossey, L.J. (1991) Thermal degradation of aqueous oxalate species. Geochim. Cosmochim. Acta 55, 15151527.
Eberl, D.D. (1993) Three zones for illite formation during burial diagenesis and metamorphism. Clays Clay Miner. 41, 2637.
Eberl, D.D. & Hower, J. (1976) Kinetics of illite formation. Bull. Geol. Soc. Am. 87, 132–1330.
Eberl, D.D. & Środotń, J. (1988) Ostwald ripening and interparticle-diffraction effects for illite crystals. Am Miner. 73, 1335-1345.
Eberl, D.D., Velde, B. & Mccormick, T. (1993) Synthesis of illite-smectite from smectite at earth surface temperatures and high pH. Clay Miner. 28, 49–60.
Fein, J.B. (1991) Experimental study of aluminium-oxalate complexing at 80°C Implications for the formation of secondary porosity within sedimentary reservoirs. Geology 19, 10371040.
Furrer, G., Zysett, M. & Schindler, P.W. (1993) Weathering kinetics of montmorillonite: Investigations in batch and mixed-flow reactors, Pp. 243-262. in: Geochemistry of Clay Pore Fluid Interactions (Manning, D.A.C., Hall, P.L. & Hughes, C.R., editors) Mineralogical Society/ Chapman & Hall, London.
Gites, M.R. & Deboer, R.B. (1990) Origin and significance of redistributional secondary porosity. Mar. Pet. Geol. 7, 378397.
Harrison, N.J. & Thyne, G.D. (1992) Predictions of diagenetic reactions in the presence of organic acids. Geochim. Cosmochim. Acta 56, 565586.
Hower, J., Eslinger, E., Hower, M.E. & Perry, E.A. (1976) Mechanism of burial metamorphism of argillaceous sediments—1. Mineralogical and chemical evidence. Bull. Geol. Soc. Am. 87, 725737.
Huang, W.L., Longo, J.M. & Pevear, D.R. (1993) An experimentally derived kinetic model for smectite-toillite conversion and its use as a geothermometer. Clays Clay Miner. 41, 162177.
Inoue, A., Kohyama, N., Kitagawa, R. & Watanabe, T. (1987) Chemical and morphological evidence for the conversion of smectite to illite. Clays Clay Miner. 35, 111120.
Inoue, A., Velde, B., Meunier, A. & Toucharo, G. (1988) Mechanism of illite formation during smecite to illite conversion in a hydrothermal system. Am Miner. 73, 13251334.
Johnson, J.W., Oelkers, E.H. & Helgeson, H.C. (1992) SUPCRT92: software package for calculating the standard molar thermodynamic properties of minerals, gases aqueous species, and reaction from 1 to 5000 bars and 0° to 1000°. Computers Geosci. 18, 899947.
Nadeau, P.H., Wilson, M.J., Mchardv, W.J. & Tarrj W. (1985) The conversion of smectite to illite during diagenesis: Evidence from some illitic clays from bentonites and sandstones. Mineral. Mag. 49, 393400.
Pearson, M.J. & Small, J.S. (1988) Illite-smectite diagenesis and palaeotemperatures in northern North Sea Quaternary to Mesozoic shale sequences. Clay Miner. 23, 109132.
Powell, T.G., Foscolos, A.E., GUNTHERP.R. & Snowoon, L.R. (1978) Diagenesis of organic matter and fine clay minerals: a comparative study. Geochim. Cosmochim. Acta 42, 11811197.
Seyfried, W.E., Janecky, D.R. & Berndt, H.E. (1987) Rocking autoclaves for hydrothermal experiments II. The flexible reaction-cell system. Pp. 216-239 in: Hydrothermal Experimental Techniques. (Ulmer, G.C. & Barnes, H.L., editors). John Wiley, New York.
Small, J.S. (1993a) An experimental study of the thermal and redox stability of dicarboxylic acid anions and their aluminium complexing behaviour. Pp. 420-422 in: Geofluids 93, Contributions to an International Conference on Fluid Evolution Migration and Interaction in Rocks. (Parnell, J., Ruffell, A. & Moles, N., editors). Geological Society, London.
Small, J.S. (1993b) Experimental determination of the rates of precipitation of authigenic illite and kaolinite in the presence of aqueous oxalate and comparison to the K/Ar ages of authigenic illite in reservoir sandstones. Clays Clay Miner. 41, 191208.
Small, J.S. & Manning, D.A.C. (1993) Laboratory reproduction of morphological variation in petroleum reservoir clays: monitoring of fluid composition during illite precipitation. Pp. 181-212. in: Geochemistry of Clay Pore Fluid Interactions (Manning, D.A.C., Hall, P.L. & Hughes, C.R., editors) Mineralogical Society/Chapman & Hall, London.
Surdam, R.C., Crossey, L.J., Hagen, E.S. & Heasler, H.P. (1980) Organic-inorganic interactions and sandstone diagenesis. Bull. Am. Assoc. Petrol. Geol. 73, 123.
Whitney, G. (1990) Role of water in the smectite-to-illite reaction. Clays Clay Miner. 38, 343350.
Whitney, G. & Northrop, H.R. (1988) Experimental investigation of the smectite to illite reaction: Dual reaction mechanisms and oxygen-isotope systematics. Am. Miner. 73, 7790.
Whitney, G. & Velde, B. (1993) Changes in particle morphology during illitization: An experimental study. Clays Clay Miner. 41, 209218.
Wolery, T.J. (1992) EQ3/6, A Software Package for Geochemical Modeling of Aqueous Systems: Package Overview & Installation Guide (Version 7). Lawrence Livermore Laboratory, University of California, Livermore, California. (UCRL-MA-110662).
Yau, Y.C., Peacor, D.R. & Mcdowell, S.D. (1987a) Smectite-to-illite reactions in Salton Sea shales: A transmission and analytical electron microscopy study. J. Sed. Pet. 57, 335342.
Yau, Y.C., Peacor, D.R., Essene, E.J., Lee, J.H., Kuo, L.C. & Cosca, M.A. (1987b) Hydrothermal treatment of smectite, illite and basalt to 460°C: Comparison of natural with hydrothermally formed clay minerals. Clays Clay Miner.. 35, 241250.

Related content

Powered by UNSILO

Fluid composition, mineralogy and morphological changes associated with the smectite-to-illite reaction: an experimental investigation of the effect of organic acid anions

  • J. S. Small (a1)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.