Frictional and microanalytical data of basalts sheared with pressurized H2O- and CO2- rich fluids

Here we report the raw data of the friction experiments performed on basalt-built faults pressurized with de-ionized H2O, pure CO2, pure Ar, and H2O+CO2 mixtures, respectively (Dataset_friction_basalts.zip). The experiments were designed to assess the effects of the fluid chemistry on fault reactivation in faults juxtaposing basalts with different state of hydrothermal alteration. The experiments setup and data are further described in Giacomel et al (2018) to which these data are supplementary material. Laboratory faults were deformed at a constant normal stress over the range from 10 to 20 MPa, at a shear stress of 5 MPa and a starting fluid pressure from 0.5 to 5 MPa. Fluid pressure was increased stepwise of 0.1 MPa/100 s up to induce macroscopic frictional instability, i.e. the equivalent to a main shock in nature. Our mechanical data point to the paucity of any significant chemical weakening due to fluid-rock interation, regardless of the composition of the injected fluid and the degree of hydrothermal alteration of basalts. Moreover, microRaman investigation evidenced a few carbonate patches at the end of the tests performed in H2O+CO2 mixtures (Dataset_raman_calcite_s1018.txt and Dataset_raman_dolomite_s1018.txt).