Carbonation of Serpentinite in Creeping Faults of California

Several large strike slip faults in central and northern California accommodate plate motions through aseismic creep. Although there is no consensus regarding the underlying cause of aseismic creep, aqueous fluids and mechanically weak, velocity-strengthening minerals appear to play a central role. This study integrates field observations and thermodynamic modeling to examine possible relationships between the occurrence of serpentinite, silica-carbonate rock, and CO2-rich aqueous fluids in creeping faults of California. Our models predict that carbonation of serpentinite leads to the formation of talc and magnesite, followed by silica-carbonate rock. While abundant exposures of silica-carbonate rock indicate complete carbonation, serpentinite-hosted CO2-rich spring fluids are strongly supersaturated with talc at elevated temperatures. Hence, carbonation of serpentinite is likely ongoing in parts of the San Andres Fault system and operates in conjunction with other modes of talc formation that may further enhance the potential for aseismic creep, thereby limiting the potential for large earthquakes.

Automated summary

This study investigates the relationships between serpentinite, silica-carbonate rock, and CO2-rich aqueous fluids in creeping faults of California. The carbonation of serpentinite is found to play a crucial role in aseismic creep, leading to the formation of talc and magnesite. These findings have significant implications for understanding the mechanisms behind earthquake generation in the California region.