Yield stress and jamming in concentrated suspensions of particles in viscous liquids

Presence of crystals significantly influences magma dynamics from mush zone inside the magma chamber to Pinian eruptions of basaltic magma with abundant microlites. We measure the strain and stress-dependent viscosity of poly-disperse suspensions of micron-size (3 -100 micron) particles in silicone oil (10-100 Pa s), at packing fraction of >70%. We find over three orders of magnitude changes in relative viscosity and yield strengths of >1000 Pa s. Particle packing fractions were determined using tap-density measurements and our results are consistent for both, simple and oscillatory shear tests. We integrate our rheological findings of yield strength, strain and strain rate dependent melt rheology to evaluate crystalline magma dynamics.