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GEOREF RECORD

Illitization of kaolinite; the effect of pressure on the reaction rate

Marco Mantovani and Ana Isabel Becerro
Illitization of kaolinite; the effect of pressure on the reaction rate
Clays and Clay Minerals (December 2010) 58 (6): 766-771

Abstract

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 ( nearly equal 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 degrees 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.


ISSN: 0009-8604
EISSN: 1552-8367
Coden: CLCMAB
Serial Title: Clays and Clay Minerals
Serial Volume: 58
Serial Issue: 6
Title: Illitization of kaolinite; the effect of pressure on the reaction rate
Affiliation: Instituto de Ciencia de Materiales, Departamento de Quimica Inorganica (CSIC-US), Seville, Spain
Pages: 766-771
Published: 201012
Text Language: English
Publisher: Clay Minerals Society, Clarkson, NY, United States
References: 11
Accession Number: 2011-019916
Categories: Geochemistry of rocks, soils, and sedimentsSedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, 1 plate
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Clay Minerals Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201112
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