Effect of pressure on the deformation of quartz aggregates in the presence of H2O

Abstract

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

“…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).…”

“…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).…”

“…It is noteworthy that the earlier ε-stepping experiments (e.g., Nègre et al, 2021, Pongrac et al, 2022 required higher strain to achieve steady-state conditions. Yet, we can express all the previously obtained experimental results from different groups using coarse-grained natural quartzites based on similar ε dependencies on σ and T as our mechanical data.…”

“…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.…”

“…The finest grain size samples are expected to show a contribution of grain size sensitive (GSS) diffusion creep as is found in polycrystalline mineral aggregates of olivine, or clinopyroxene (Yabe et al, 2020;Ghosh et al, 2021). Importantly, different interpretations for the grain-scale deformation mechanisms, from climb-controlled dislocation creep to a combination of dislocation and diffusion creep for quartz were postulated among different studies (G&T95; Richter et al, 2018;Fukuda et al, 2018;Nègre et al, 2021). In other words, it still remains difficult to constrain the intra-and inter-grain processes responsible for plastic deformation and related flow law parameters.…”