A New Insight into the Nature of the Leached Layers Formed on Basaltic Glasses in Relation to the Choice of Constraints for Long Term Modelling

• Published in: MRS Proceedings
• Main Authors: Crovisier, J. L., Atassi, H., Daux, V., Honnorez, J., Petit, J. C., Eberhart, J. P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 1988
• Subjects: General Engineering; Iceland
• Online Access: http://dx.doi.org/10.1557/proc-127-41; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400539451

ABSTRACT Experimental basaltic glass dissolution in fresh water is compared with analyses made on subglacial hyaloclastites from Iceland. The dissolution is initially selective and remains selective if the solution is renewed, whereas it becomes apparently congruent in non-renewed conditions. The congruent dissolution is ascribed to a pH increase (up to 7.0–7.5) which is hampered in the former conditions. The palagonite hydrated layer on the Icelandic basaltic glasses is made up of amorphous to crystallized clay-like materials. The chemical composition of palagonite is close to that of the intergranular clayey material, thus, it is inferred that in most cases no significant chemical gradient exists in the solution between the reaction zone, namely the glass/palagonite interface, and the intergranular solution. We conclude that the dissolution of basaltic glass under subglacial conditions is controlled by thermodynamics and that kinetic constraints, such as the diffusion of species through the altered layers, do not play a major role.