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Illite neoformation in plagioclase during weathering: Evidence from semi-arid Northeast Brazil

Bétard François, Caner Laurent, Gunnell Yanni, Bourgeon Gérard. 2009. Illite neoformation in plagioclase during weathering: Evidence from semi-arid Northeast Brazil. Geoderma, 152 (1-2) : pp. 53-62.

Journal article ; Article de revue à facteur d'impact
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Quartile : Q1, Sujet : SOIL SCIENCE

Abstract : Illite minerals in soils and weathered rocks are usually interpreted as secondary clays derived from the transformation of primary rock-forming minerals with similar properties (e.g. muscovite), or as direct products of hydrothermal alteration after feldspar (i.e. sericite). With the help of detailed investigations involving X-ray diffraction, scanning electron microscopy and X-ray element mapping, this study testifies to the neoformation of illite inside plagioclase feldspar crystals after their partial dissolution in the weathering zone of Luvisols in semi-arid Northeast Brazil. Our results thus reveal that meteoric weathering can produce illite not only from mica, i.e., by a transformation process, but also within non-alkali feldspar by a neoformation process, at least under the semi-arid conditions that have long prevailed in the study area. Given that illite in weathering mantles has recurrently been attributed, often by default, to hydrothermal processes, results shown here provide new focus to an alternative pathway of illite formation primarily controlled by climate. (Résumé d'auteur)

Mots-clés Agrovoc : Silicate, Minéral argileux, Potassium

Mots-clés géographiques Agrovoc : Ceara

Mots-clés géographiques complémentaires : Nordeste

Classification Agris : P33 - Soil chemistry and physics
P40 - Meteorology and climatology

Champ stratégique Cirad : Hors axes (2005-2013)

Auteurs et affiliations

  • Bétard François, Université de Paris-Val-de-Marne (FRA)
  • Caner Laurent, Université de Poitiers (FRA)
  • Gunnell Yanni, CNRS (FRA)
  • Bourgeon Gérard, CIRAD-PERSYST-UPR Recyclage et risque (FRA)

Autres liens de la publication

Source : Cirad - Agritrop (https://agritrop.cirad.fr/550168/)

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