Measuring pressure-solution mitigated friction forces between calcite surfaces with an extended surface forces apparatus
Yjiue Diao, Rosa M. Espinosa-Marzal
The friction between two adjacent tectonic plates under shear loading may dictate seismic activities, while water has been recognized to alter the fault dynamics and earthquake nucleation. Recently, we have investigated the frictional behavior of a single-asperity contact composed of a naturally oxidized silicon AFM tip and an atomically flat calcite surface, which was selected as a model of reactive carbonate-based rock in nature. A pressure-solution facilitated slip has been identified to be a possible friction weakening mechanism of calcite-rich fault materials at high applied pressures and sufficiently slow sliding velocities. In this work, we aim to further scrutinize the effect of the interfacial composition on the pressure solution of calcite, and on the frictional characteristics and weakening mechanisms of single-asperity calcite contacts in aqueous solution. We have extended our surface forces apparatus (SFA) to measure the deformation of atomically flat substrates like calcite and to quantify the pressure solution kinetics as a function of the applied load and solution composition, while friction is concurrently measured. The findings of this novel study directly contribute to the understanding of mechanisms underlying the frictional strength of fault rocks in presence of aqueous solutions. More broadly, the development of a new methodology for the investigation of interfacial reactions between mineral surfaces expands the range of applications of the SFA.