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Illitization of Kaolinite: The Effect of Pressure on the Reaction Rate

Published online by Cambridge University Press:  01 January 2024

Marco Mantovani  and
Ana Isabel Becerro
Marco Mantovani*
Affiliation:
Instituto de Ciencia de Materiales, Departamento de Química Inorgánica (CSIC-US), c/ Américo Vespucio, 49, 41092 Sevilla, Spain
Ana Isabel Becerro
Affiliation:
Instituto de Ciencia de Materiales, Departamento de Química Inorgánica (CSIC-US), c/ Américo Vespucio, 49, 41092 Sevilla, Spain
*
* E-mail address of corresponding author: [email protected]
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Abstract

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Studies of the paragenesis of authigenic illite in arkosic sandstones of various regions and ages have revealed that the illitization of kaolinite is an important reaction accounting for the formation of authigenic illite in sandstones during burial diagenesis. The illitization of kaolinite takes place at an intermediate burial depth of 3–4 km, where pressure can reach values of 100 MPa (≈ 1000 bars). The purpose of the present study was to analyze the effect of pressure on the rate of kaolinite illitization in alkaline conditions. Hydrothermal reactions were conducted on KGa-1b kaolinite in KOH solution at 300°C and under pressures of 500, 1000, and 3000 bars for 1 to 24 h. The visual examination of the X-ray diffraction (XRD) patterns indicated a notable influence of pressure on the reaction rate. Molar percentages of muscovite/illite formed at each time interval were calculated from the analysis of two diagnostic XRD peaks, representing the 060 reflections of kaolinite and muscovite/illite. The data were modeled to obtain the initial rate of conversion at each pressure. The results indicated that the initial rate of kaolinite to muscovite/illite conversion is one order of magnitude greater at 3000 bars than at 500 or 1000 bars. Comparison of these data with those in the literature show a faster conversion rate (several orders of magnitude) in an initially high-alkaline solution than in a near-neutral solution.

Keywords

Hydrothermal ReactionKaoliniteKOHMuscovite/illitePressureReaction RateXRD
Type
Article
Information
Clays and Clay Minerals , Volume 58 , Issue 6 , December 2010 , pp. 766 - 771
Copyright
Copyright © Clay Minerals Society 2010

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