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Coupled fluctuations in element release during dolomite dissolution

Published online by Cambridge University Press:  05 July 2018

Christine V. Putnis ,
Encarnación Ruiz-Agudo  and
Jörn Hövelmann
Christine V. Putnis*
Affiliation:
Institut für Mineralogie, Universität Münster, Corrensstrasse 24, 48149, Münster, Germany
Encarnación Ruiz-Agudo
Affiliation:
Dept. Mineralogy and Petrology, University of Granada, Fuentenueva s/n, 18071 Granada, Spain
Jörn Hövelmann
Affiliation:
Institut für Mineralogie, Universität Münster, Corrensstrasse 24, 48149, Münster, Germany
*
* E-mail: putnisc@nwz.uni-muenster.de
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Abstract

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Atomic force microscopy has been used to determine more precisely the mechanism of the initial stages of dolomite dissolution. Analysis of outflow solutions initially shows fluctuations of both Ca and Mg release with concentrations of Ca >> Mg. The dolomite surface dissolves congruently in the presence of slightly acidified water as confirmed by the regular spreading of characteristic rhombohedral etch pits. Direct in situ observations show that a new phase precipitates on the dissolving surface simultaneously. As the Ca and Mg release decreases with time, the precipitated phase can be seen to spread across the dolomite surface. These observations indicate that the apparent incongruent dissolution of dolomite is a two-step process involving stoichiometric dissolution with the release of Ca, Mg and CO3 ions to solution at the mineral–fluid interface coupled with precipitation of a new Mg-carbonate phase. The coupled element release confirms the interface-coupled dissolutionprecipitation mechanism.

Keywords

dolomitedissolutioninterface-coupled dissolution-precipitationincongruent dissolution
Type
Research Article
Information
Mineralogical Magazine , Volume 78 , Issue 6 , November 2014 , pp. 1355 - 1362
Creative Commons
Creative Common License - CCCreative Common License - BY
© [2014] The Mineralogical Society of Great Britain and Ireland. This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY) licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2014

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