Carbonate-based rocks, such as limestone and dolomite, abound in lithosphere. When the mineral surface is compressed by a counter-surface in aqueous environment, surface forces are responsible for the presence of a thin film of aqueous solution that remains confined between the two mineral surfaces. This thin film provides a pathway for the ions and water to diffuse into the confined space and react with the mineral surfaces, which leads to several geochemical phenomena. In this work, calcite is selected as the model mineral and Atomic Force Microscopy is used to perform surface force measurements in electrolytes with a wide range of geologically relevant compositions. Both DLVO forces and non-DLVO forces are scrutinized with nanoscale resolution to reveal the electrochemical surface properties and the composition of the confined calcite-solution interface with molecular insight. The comparison between two electrolytes, NaCl and CaCl<sub>2</sub> solutions, reveals ion-specific effects of the interfacial composition, reflecting the difference in the structure of the calcite’s hydration layer. When the confining pressure is high, pressure solution of the mineral occurs and our novel studies with an extended Surface Forces Apparatus provide new (nanoscale) insight of this process. Broadly speaking, this work brings about implications for diverse areas of inquiry, such as nanoconfined biomineralization, CO<sub>2</sub> sequestration in porous aquifers, and pressure solution and crystallization in confined hydrosystems.

Molecular insight into the properties of the nanoconfined calcite-solution Interface

2019 Fall National Meeting

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