Temperature Dependence of Fault Frictional Healing in Quartz Gouges at Hydrothermal Conditions

Fault healing allows the accumulation of stress along faults during interseismic periods. In this critical stage, temperature-dependent fluid-rock interactions within fault zones become crucial at seismogenic depth in controlling fault strength recovery. However, frictional healing at hydrothermal conditions is still underexplored. We conducted hydrothermal friction experiments to investigate the temperature dependence of fault healing in quartz gouges, performing slide-hold-slide tests with a rotary shear apparatus. Quartz gouges (with different initial grain sizes) were sheared for large slip distances (up to ∼90 mm), subjected to temperatures of 23, 100, 200, and 400°C, pore fluid pressures of 6 and 36 MPa and effective normal stresses of 10 and 20 MPa. This allowed us to explore the role of temperature, strain and fluid state (liquid, vapor or supercritical) on friction and frictional healing. Our results reveal that temperature-enhanced reaction kinetics of quartz-water interaction increases fault healing which is governed by a combination of competing deformation mechanisms. Microstructural observations and data analysis show that cataclastic processes at low temperatures progressively give way to dissolution-precipitation processes at high temperatures, promoting elevated frictional healing. Theoretical modeling suggests an activation energy Q = 40 kJ/mol for the underlying rate-limiting processes, which is consistent with a fault strengthening mechanism regulated by subcritical crack growth and pressure solution. Finally, we propose a novel formulation to incorporate the temperature dependence of fault healing in quartz gouge into classical empirical laws for frictional healing, providing a quantitative framework to describe fault strength at seismogenic depths in the Earth's crust.