Mechanical properties and recrystallization of quartz in presence of H2O: Combination of cracking, subgrain rotation and dissolution-precipitation processes

Quartz rheology constrained from constant-load experiments: Consequences for the strength of the continental crust

“…Another advantage of load-stepping is that the bulk strain of the sample is smaller than in ε-stepping tests, so that geometrical problems due to change in the sample shape are minimized. We compare our results with εstepping experiments using the same Tana quartzite to understand the effect of much larger final strain, hence, significant recrystallization (Pongrac et al, 2022). A comparison between our newly established flow law with previous results provides the opportunity to further explore the effects of using different apparatuses, choice of the sample, and the deformation mechanism on the mechanical properties of wet quartzite.…”

“…3b, c). A recent communication (Pongrac et al, 2022) has reported n ≈ 2 from co-axial ε-stepping experiments using the same Tana quartzite. These experiments (plotted as PP in Fig.…”

“…The mean grain size is ∼200 μm and the H 2 O has been measured as of the order of ∼1700 H/10 6 Si for grain interiors and ∼2100 H/10 6 Si for grain boundaries in a previous study (Nègre et al, 2021). Further details on chemical and microstructural characterizations of the starting material can be found in Nègre et al (2021) and Pongrac et al (2022). Deformed samples were cut through the centre, parallel to the compression direction, and then characterized using Polarized light microscopy (LM), SEM-cathodoluminescence (CL) and Electron backscatter diffraction (EBSD) (see supplementary text S1).…”

“…Due to the filling of the pore space by authigenic SiO 2 cement, no visible porosity was detected by the LM or SEM. Detailed microstructural characterizations and H 2 O content of the deformed (Tana) samples have been presented in two earlier studies (Nègre et al, 2021;Pongrac et al, 2022). Therefore, in the present contribution, we will only summarize the microstructural observations and put the observed grain-scale deformation mechanism into context with our new flow law data.…”

“…5e). Such 'axial splitting' cracks typically form at low confining pressures, most likely early in the experimental procedure, before attaining the deformation conditions (Pongrac et al, 2022). These mode-I cracks are volumetrically small (<1%) and discrete.…”