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The dependence of albite feldspar dissolution kinetics on fluid saturation state at acid and basic pH: Progress towards a universal relation

By Roland Hellmann, Damien Daval and Delphine Tisserand

Abstract

International audienceHere we report on two separate ongoing, multi-year investigations on the dependence of the dissolution rate (R) of albite feldspar on fluid saturation state, as defined by the Gibbs free energy of reaction (ΔGr) for dissolution. The investigations are based on dissolution at pH 9.2, 150 °C and pH 3.3, 100 °C. Both studies reveal that the R–ΔGr relation is highly non-linear and sigmoidal. The kinetic data from the first study, being the most complete, can be fitted with a sigmoidal rate curve that is composed of two separate, parallel rate laws that represent distinct mechanisms of dissolution. The switch between one dominant mechanism and the other may be controlled by a critical free energy. The fact that in both studies the same type of sigmoidal R–ΔGr relation exists for dissolution at different pH and temperature condition suggests that this behavior may be universal for albite and other feldspars. Moreover, the experimental data contradict the commonly used R–ΔGr relation that is loosely based on transition state theory (TST). This has important implications with respect to the accuracy of geochemical codes that model water–rock interactions at near-equilibrium conditions

Topics: Feldspar, Albite, Dissolution, Kinetic rate laws, Gibbs free energy, Water–rock interaction, CO2 sequestration, [ SDU.STU.GC ] Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [ SDE.MCG ] Environmental Sciences/Global Changes
Publisher: Elsevier Masson
Year: 2010
DOI identifier: 10.1016/J.CRTE.2009.06.004
OAI identifier: oai:HAL:insu-00565084v1
Provided by: Hal-Diderot
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