Nanoscale Insight Into Tribomechanical and Hydrothermal Process at Calcite Surface
Advisor: Professor Rosa M. Espinosa-Marzal
Teams: : https://teams.microsoft.com/l/meetup-join/19%3ameeting_NzhjNzQyMTgtMmI5Yi00ZTNmLTlmODUtMmNkNjdhMTFiY2Vm%40thread.v2/0?context=%7b%22Tid%22%3a%2244467e6f-462c-4ea2-823f-7800de5434e3%22%2c%22Oid%22%3a%22e0061843-43f7-4cd3-ae19-2fef0f697af2%22%7d
Abstract:
Fault slip and earthquake nucleation are controlled by interfacial processes that operate at the nanoscale, where chemical, mechanical, and thermal effects converge to regulate frictional behavior. Calcite-bearing rocks are abundant in the lithosphere, and they are particularly significant due to its ductility and its strong propensity for dissolution and precipitation. These processes, commonly described as pressure solution and cementation, actively reconstruct calcite surfaces in aqueous environments and are hypothesized to play a decisive role in modulating fault behaviors. Yet, the mechanisms linking nanoscale interfacial processes with macroscopic fault slip remain poorly understood. Our goal is to investigate the tribomechanical behavior of calcite and provide fundamental understanding to connect nanoscale interfacial dynamics with macroscopic fault mechanics. To achieve this objective, ion-specific effects, surface roughness, and hydrothermal conditions were examined, and calcite’s mechanochemical and tribomechanical behavior was modeled within the rate-and-state friction framework.
Surface force measurements—including friction, hydration, and Derjaguin–Landau–Verwey–Overbeek (DLVO) forces—were conducted using atomic force microscopy (AFM) under various conditions. Load-dependent friction measurements in Ca²⁺, Mg²⁺, and Ni²⁺ solutions, paired with in situ calcite thickness analysis by Surface Force Apparatus (SFA), revealed that confined fluid chemistry and ion–surface interactions regulate the onset and magnitude of pressure solution, thereby affecting frictional strength. Velocity-dependent friction studies on polished calcite surfaces of varying grain size demonstrated that nanoscale roughness promotes aseismic slip, whereas the presence of water suppresses the roughness effect by activating pressure solution. The temperature-dependent friction measurements at nanoscale provide thorough insights into the complex change of calcite surface. At elevated temperatures, AFM measurements under dry conditions revealed competition between stick–slip and reduction in energy barrier for thermally activated slip, accompanied by surface reconstruction through hydration layer. In comparison, hydrothermal experiments with calcite probes demonstrated the frictional weakening behavior in solution for the first time, and both the evolution of contact area and bond quality, which is related with changes in interfacial ion structures, were carefully monitored and contribute to advancement in RSF model.
The findings of this research employed nanoscale evidence to inspect the influence of water, surface roughness, and temperature on the interfacial reactions occurring on calcite, which has advanced the fundamental knowledge of tribomechanical processes at fault interface. These results support the extension of the RSF framework to nanoscale contacts and motivate a generalized friction model that incorporates chemical, mechanical, and thermal effects. In the context of earthquake science, this work helps to identify the microphysical conditions that favor either stable creep or unstable slip in carbonate-bearing faults, contributing to improved models of earthquake nucleation in the seismogenic zone. More broadly, the tribomechanical and mechanochemical understandings can inform strategies for subsurface engineering applications where calcite is abundant, including carbon sequestration, geothermal energy production, and hydrocarbon recovery. By bridging nanoscale processes with fault-scale behavior, this research not only enriches the theoretical framework of rock slip but also provides a scientific foundation for anticipating and mitigating seismic hazards in carbonate-dominated geological systems.