Solid-state sintering can cause explosivity and seismogenic unstable sliding during dome-building eruptions

Data accompanying manuscript of the same name.

The hydraulic and rheological properties of the shear zones that develop during lava dome eruptions govern the potential for explosive and seismic behavior at those volcanoes. In previous hot-pressing experiments we showed solid-state sintering can cause the crystalline gouge that fills volcanic shear zones to lose porosity and permeability and lithify on the timescale of years. We present the results of torsion experiments in which we document, for the first time, the rheological behavior of gouge at the temperature-normal stress-strain rate conditions expected in volcanic shear zones, and determine the effect of shear on the rate of solid-state sintering. Gouge sheared at 500°C, 50 or 100 MPa normal stress and 10-4 to 10-3 s-1 does not sinter, exhibits strain-independent behavior and deforms by distributed granular flow. In contrast, gouge sheared at 900°C, 50 or 100 MPa normal stress and 10-5 to 10-3 s-1 is sintered, exhibits strain-weakening behavior and shows microstructural evidence of strain localization as well as significant lithification. Samples sheared at 900°C for <1 h have measured final porosities and permeabilities comparable to gouge samples hot-pressed at the similar temperature-pressure conditions for 60 h, indicating shearing significantly enhances sintering. We use results to develop a model that can predict time-temperature-pressure-dependent densification by solid-state sintering under both static conditions and during shear. Finally, we propose that sintering-driven lithification can cause deforming shear zones to transition from aseismic stable sliding to unstable seismogenic sliding, perhaps resulting in the drumbeat seismicity observed at dome-building volcanoes.

Included in data repository:
- experimental log, including conditions of experiment, date, sample dimensions, UMN Paterson ID number, etc.
- mechanical data for all deformation experiments
- mechanical data for experiments used for jacket correction
- measured porosities, determined by image analysis
- BSE images used for image analysis
- measured permeabilities, determined using flow-through permeameter
- BSE mosaics (in power point, affinity designer, pdf files) for all samples