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Amphibole weathering in a glaucophane-schist (Île de Groix, Morbihan, France)

Published online by Cambridge University Press:  09 July 2018

D. Proust
D. Proust*
Affiliation:
ERA no. 220 du CNRS “Pédologie, Pétrologie et Métallogénie de la Surface”, Université de Poitiers, 86022 Poitiers Cédex, France
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Abstract

The weathering of two co-existing sodic (glaucophane) and calcic (actinolite) amphiboles in a glaucophane-schist was studied by optical microscopy. XRD and the electron microprobe. In the early stages of weathering, two trioctahedral expandable phases occur as internal weathering products in the amphiboles: a sodic saponite in the glaucophane and a calcic ‘hectorite’ in the actinolite. Further weathering leads to the replacement of the ‘hectorite’ by a calcic saponite in the actinolite, while the saponites formed in the weathered glaucophane exhibit progressive calcium enrichment in their interlayer sites. These observations demonstrate the influence of the primary mineral compositions on initial weathering products.

Type
Research Article
Information
Clay Minerals , Volume 20 , Issue 2 , June 1985 , pp. 161 - 170
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1985

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