Experimental investigation of chemically aided fracture growth in silicified fault rocks

•Subcritical fracture growth in silicified rocks depends on chemical environment.•Aqueous conditions increase fracture velocity by up to two orders of magnitude.•Fracture propagation velocity depends on dissolution rate at fracture tips.•Elevated temperature, pH, salinity promote fracture growth in silicified rocks. Using double-torsion load-relaxation tests, we evaluated the effect of chemical environment on fracture toughness and subcritical fracture growth index (SCI) in silicified fault rocks collected in the vicinity of the Dixie Valley, NV, geothermal system. Testing environments included: ambient air, deionized water, dilute HCl, NaOH, and NaCl solutions, and deionized water at elevated temperatures. We observed reductions in SCI in all aqueous environments, with >60% reduction in alkaline solutions. These results suggest that physiochemical conditions in hydrothermal systems may facilitate fracture growth, with chemically aided fracture growth and flow conduit formation competing with precipitation and sealing in reactive systems.