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Authigenic kaolin and illitic minerals during burial diagenesis of sandstones: a review

Published online by Cambridge University Press:  09 July 2018

B. Lanson*
Affiliation:
Environmental Geochemistry Group, LGIT-IRIGM, CNRS - University of Grenoble, 38041 Grenoble Cedex 9, France
D. Beaufort
Affiliation:
HydrASA, University of Poitiers - CNRS, 40 av. Recteur Pineau, 86022 Poitiers Cedex, France
G. Berger
Affiliation:
Geochemistry Lab., CNRS - University Paul Sabatier, 38 rue des Trente-Six Ponts, 31400 Toulouse, France
A. Bauer
Affiliation:
For schungszentrum Karlsruhe, Institut für Nukleare Entsorgungstechnik, PO Box 3640, 76021 Karlsruhe, Germany
A. Cassagnabère
Affiliation:
Etudes Recherches Matériaux, Espace 10 - République 2, Rue A. Haller, 86000 Poitiers, France
A. Meunier
Affiliation:
HydrASA, University of Poitiers - CNRS, 40 av. Recteur Pineau, 86022 Poitiers Cedex, France

Abstract

The diagenetic evolution of kaolin and illitic minerals in sandstones is described here. The structural characterization of these minerals, the possible reaction pathways leading to their crystallization, and the origin of the fluids involved are discussed specifically.

While early precipitation of kaolinite is in general related to flushing by meteoric waters, subsequent diagenetic kaolinite-to-dickite transformation probably results from invasion by acidic fluids of organic origin. Dickite is the stable polytype in most sandstone formations and the kaoliniteto- dickite conversion is kinetically controlled.

The conventional model of kaolin illitization, assuming a thermodynamic control in a closed system, is discussed and compared to an alternative model in which illitization of kaolin is not coupled to dissolution of K-feldspar (Berger et al., 1997). In the latter model, illite crystallization at the expense of kaolin implies that an energy barrier is overcome either by an increased K+/H+ activity ratio in solution or by a considerable temperature increase.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2002

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