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(Ed.)
Core samples from International Ocean Discovery Program (IODP) Expedition 366 were tested in the laboratory to determine permeability, porosity, density, and frictional strength and their relation to mineralogy as part of an effort to understand hydromechanical processes at convergent plate margins. Seven samples were tested from a depth range of 19.6 to 197.9 m below seafloor. The samples were derived from three serpentinite mud volcanoes in the Mariana forearc region that formed where slab-derived fluids and materials ascend along faults. The physical characteristics mirror compositional differences between predominantly serpentine-rich and saponite-rich samples. Permeability values ranged from 10−17 to 10−19 m2, low enough to facilitate the formation of high fluid pressures that have been observed in the Mariana and other subduction megathrust environments. Porosity ranged from 0.37 to 0.51 and density ranged from 1.66 to 2.01 g/cm3. Serpentine-rich samples have coefficients of friction of 0.2–0.4, consistent with crustal serpentinite from a variety of fault zones, whereas saponite-rich samples have friction values less than 0.2, consistent with saponite fault gouge from the San Andreas Fault Observatory at Depth (SAFOD) drill hole in California (USA).
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