Abstract

Pressure solution of carbonate-based rocks participates in many geophysical and geochemical processes occurring at or near the Earth’s surface, but fundamental knowledge is still lacking. Here, the pressure solution of calcite single crystals in water, NaCl and CaCl2 brines was investigated with an extended surface forces apparatus (SFA). This highly mechanically and thermally stable measuring technique enables to measure the deformation of two single calcite crystals undergoing pressure solution and the deformation rates with high precision as a function of load and fluid composition. The measurements in water reveal both diffusion- and dissolution-limited scenarios. Further, the pressure solution of calcite decelerates with a small concentration of NaCl compared to CaCO3-saturated solution, while the rate is promoted with an increase to 100 mM NaCl, reflecting the competition of at least two different mechanisms. In contrast, the addition of small concentrations of CaCl2 already speeds up calcite’s pressure solution. These experimental results cannot be solely explained via the increase in solubility of calcite with ionic strength, as generally proposed. Instead, they are consistent with the ion-specific effects of the interfacial composition and the distortion of the hydration structure of calcite under an applied pressure smaller than ∼25 MPa. This work advances the fundamental knowledge of pressure solution of calcite. More broadly, the novel technique developed here can be applied to other brittle and unexfoliable minerals, which notably expands the applications of SFA.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.