Experimental Study of Dissolution Kinetics of K-feldspar as a Function of Crystal Structure Anisotropy under Hydrothermal Conditions

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• 作者：M. Pollet-Villard^a ; D. Daval^a ; ^b ; P. Ackerer^a ; G.D. Saldi^b ; ^c ; K.G. Knauss^b ; B. Wild^a ; B. Fritz^a ; ^{bfritz@unistra.fr}
• 关键词：experimental study ; dissolution kinetics ; anisotropy ; K-feldspar ; hydrothermal conditions
• 刊名：Procedia Earth and Planetary Science
• 出版年：2017
• 出版时间：2017
• 年：2017
• 卷：17
• 期：Complete
• 页码：165-168
• 全文大小：391 K
• 卷排序：17

文摘

We present the results of an experimental study of the effect of anisotropy on the kinetics of K-Feldspar dissolution under hydrothermal conditions as encountered in the Soultz-sous-Forêts enhanced geothermal system. We try to quantify the impact of K-feldspar anisotropy on dissolution rates in order to develop a more comprehensive model of the evolution of the reactive surface of silicate minerals in order to propose alternate kinetic rate laws to be implemented into water-rock interaction models and reactive transport codes. Our results evidence a relation between K-spar dissolution rate and the Gibbs free energy of reaction (ΔGr) which clearly differs from the transition state theory usually implemented into geochemical codes: it depends on the crystallographic orientation of K-spar mineral with significant differences between the different crystal faces. As for the far-from-equilibrium dissolution rate, this result highlights that using a unique theoretical rate law to describe dissolution rate as a function of ΔGr remains highly questionable. These results are very important for our challenge of understanding and modelling the dissolution mechanisms and they evidence that the dissolution anisotropy plays a fundamental role in these mechanisms.