Figure 1
From: Excess water storage induced by viscous strain localization during high-pressure shear experiment
Distribution of H2O across the experimental shear zone. (a) Three-dimensional section of the sample assembly used to hot-press and deform 70 wt% of fine-grained olivine (~2 µm) plus 30 wt% of coarse-grained diopside (~100 µm) at 1.2 GPa and 900 °C. While the pressure (σ3) is applied using NaCl as the confining medium, the sample is deformed within a platinum jacket by pushing on alumina pistons (σ1) partly cut at 45° of the piston axis25 (non-coaxial assembly; see Supplementary Fig. S1). After deformation, the H2O content is documented for the olivine matrix using secondary ion mass spectrometry (SIMS) in spots of 10 × 10 × 4 µm3, which necessarily includes several grain boundaries (green lines). (b) Backscattered electron (BSE) image of the strain gradient that results from localization of deformation in the top part of the sample (high-strain zone). Each spot and related colour coding refers to the measured H2O content, including the crystal lattice and grain boundaries. All analyses surrounded by a dotted circle are used in Fig. 3. (c) Mapping of the SIMS dataset across the strain gradient. The interpolation was processed using the griddata function of MATLAB with isocontours increment of 125 ppm. The white line gives the isocontour of added water before experiment. Ol = olivine; Di = diopside; FIB = Focused Ion Beam zone documented in Précigout and Stünitz25.
