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Matlab code used to analyse Melt Volume Orientation (MVO) data as shown and described in Bader, J.A., W. Zhu, L. Montési, C. Qi, B. Cordonnier, D. Kohlstedt, & J. Warren, Effects of Stress-driven Melt Segregation on Melt Orientation, Melt Connectivity and Anisotropic Permeability, Journal of Geophysical Research: Solid Earth, DOI 10.1029/2023JB028065 

Abstract Stress‐driven melt segregation may have important geochemical and geophysical effects but remains a poorly understood process. Few constraints exist on the permeability and distribution of melt in deformed partially molten rocks. Here, we characterize the 3D melt network and resulting permeability of an experimentally deformed partially molten rock containing several melt‐rich bands based on an X‐ray microtomography data set. Melt fractions range from 0.08 to 0.28 in the ∼20‐μm‐thick melt‐rich bands, and from 0.02 to 0.07 in the intervening ∼30‐μm‐thick regions. We simulated melt flow through subvolumes extracted from the reconstructed rock at five length scales ranging from the grain scale (3 μm) to the minimum length required to fully encompass two melt‐rich bands (64 μm). At grain scale, few subvolumes contain interconnected melt, and permeability is isotropic. As the length scale increases, more subvolumes contain melt that is interconnected parallel to the melt bands, but connectivity diminishes in the direction perpendicular to them. Even if melt is connected in all directions, permeability is lower perpendicular to the bands, in agreement with the elongation of melt pockets. Permeability parallel to the bands is proportional to melt fraction to the power of an exponent that increases from ∼2 to 5 with increasing length scale. The permeability in directions parallel to the bands is comparable to that for an isotropic partially molten rock. However, no flow is possible perpendicular to the bands over distances similar to the band spacing. Melt connectivity limits sample scale melt flow to the plane of the melt‐rich bands. 

Key Points High pore fluid pressure stabilizes fault propagation in porous sandstone deformed under drained conditions Slow faulting was associated with pervasive microcracking and diffuse shear bands only in samples deformed sufficiently slow Pervasive subcritical cracking enables slow faulting at high pore fluid pressure under drained conditions at the sample scale 

The dataset includes the measurements of individual subduction zones defined in the convergence-parallel, trench-perpendicular, and spreading-parallel direction. </p>  </p> Table S3. Location of each trench, arc, and back-arc defined in a direction parallel to the convergence, and the corresponding distance from the trench to the arc (D_TA), subarc slab depth (H), and from the trench to the back-arc spreading center (D_TB). The slab dip is measured at 50km (Dip50), 100km (Dip100), and 200km (Dip200) and averaged from 0 to 50 km (Dip050), 0 to 100km (Dip0100), 0 to 200km (Dip0200), and 50 to 200km (Dip50200). </p> Table S4. Location of each trench, arc, and back-arc defined in a direction perpendicular to the trench, and the corresponding distance from the trench to the arc (D_TA), subarc slab depth (H), and from the trench to the back-arc spreading center (D_TB). The slab dip is measured at 50km (Dip50), 100km (Dip100), and 200km (Dip200) and averaged from 0 to 50 km (Dip050), 0 to 100km (Dip0100), 0 to 200km (Dip0200), and 50 to 200km (Dip50200). </p> Table S5. Location of each trench, arc, and back-arc defined in a direction parallel to the spreading direction, and the corresponding distance from the trench to the arc (D_TA), subarc slab depth (H), and from the trench to the back-arc spreading center (D_TB). The slab dip is measured at 50km (Dip50), 100km (Dip100), and 200km (Dip200) and averaged from 0 to 50 km (Dip050), 0 to 100km (Dip0100), 0 to 200km (Dip0200), and 50 to 200km (Dip50200). </p>  </p> 

Abstract The onset of brittle failure in rocks includes dilatancy and strain localization. To better understand this nucleation process, we analyze the evolution of the local three‐dimensional strain tensor using X‐ray tomograms acquired during triaxial compression experiments on granite and sandstone. The onset of the localization of the compaction, dilation, and shear strain occurs when ∼65% of the rock volume experiences dilation. Tracking the locations of the high strains throughout loading suggests that the deformation that occurs early in loading influences the location of the system‐sized fracture network that produces macroscopic failure. This influence is larger in the sandstone experiments than the granite experiments, likely due to the microstructure of the sandstone. These results have important implications for detecting precursors to catastrophic failure. 

Abstract A global study of subduction zone dynamics indicates that the thermal structure of the overriding plate may control arc location. A fast convergence rate and a steep slab dip bring a hotter mantle further into the wedge corner, forming arc volcanoes closer to the trench. Separately, laboratory and numerical experiments showed that the development of a back‐arc spreading center (BASC) is driven by the migration of the subducting hinge, especially following changes in the slab geometry. As both arc location and the deformation regime of the overriding plate depend on slab kinematics and geometry, we investigate the possible correlations between BASC, the position of volcanic arcs, and slab dip at the scale of individual subduction zones. To do this, we compare the distance from trench to arc and trench to BASC at the Mariana, Scotia, Vanuatu, Tonga, and Kermadec subduction zones. In most cases, the arc and BASC are closer to the trench when the slab is dipping steeply. The correlation could result from an interplay between progressive changes in slab geometry and overriding plate deformation. This assumes, on the one hand, that the isotherm at the apex of which the arc forms is tied to a constant slab decoupling depth and, on the other hand, that back‐arc opening accommodates a change in slab dip. As slab dip decreases, both the BASC and the apex of the isotherm controlling the melt focusing move further from the trench. The observed trends are consistent with a slab anchored at 660 km depth. 

Image data of sample QC0705, with analysis scripts and derived data 

Abstract. The continuum of behavior that emerges during fracturenetwork development in crystalline rock may be categorized into threeend-member modes: fracture nucleation, isolated fracture propagation, andfracture coalescence. These different modes of fracture growth producefracture networks with distinctive geometric attributes, such as clusteringand connectivity, that exert important controls on permeability and theextent of fluid–rock interactions. To track how these modes of fracturedevelopment vary in dominance throughout loading toward failure and thushow the geometric attributes of fracture networks may vary under theseconditions, we perform in situ X-ray tomography triaxial compressionexperiments on low-porosity crystalline rock (monzonite) under upper-crustalstress conditions. To examine the influence of pore fluid on the varyingdominance of the three modes of growth, we perform two experiments undernominally dry conditions and one under water-saturated conditions with 5 MPa ofpore fluid pressure. We impose a confining pressure of 20–35 MPa and thenincrease the differential stress in steps until the rock failsmacroscopically. After each stress step of 1–5 MPa we acquire athree-dimensional (3D) X-ray adsorption coefficient field from which weextract the 3D fracture network. We develop a novel method of trackingindividual fractures between subsequent tomographic scans that identifieswhether fractures grow from the coalescence and linkage of several fracturesor from the propagation of a single fracture. Throughout loading in all ofthe experiments, the volume of preexisting fractures is larger than that ofnucleating fractures, indicating that the growth of preexisting fracturesdominates the nucleation of new fractures. Throughout loading until close tomacroscopic failure in all of the experiments, the volume of coalescingfractures is smaller than the volume of propagating fractures, indicatingthat fracture propagation dominates coalescence. Immediately precedingfailure, however, the volume of coalescing fractures is at least double thevolume of propagating fractures in the experiments performed at nominallydry conditions. In the water-saturated sample, in contrast, although thevolume of coalescing fractures increases during the stage preceding failure,the volume of propagating fractures remains dominant. The influence ofstress corrosion cracking associated with hydration reactions at fracturetips and/or dilatant hardening may explain the observed difference infracture development under dry and water-saturated conditions.