2.2 Granular nature of crystal-rich magma reservoirs
Another obstacle towards our ability to accurately model compacting
magmatic systems is whether the deformation of these systems is suitable
for a continuum description, or if granular models which describe
individual interactions between crystals are instead required. While
magma mushes are often simplified as porous media for continuum
calculations, in reality they are complex multiphase mixtures where
forces can be transmitted at the particle-particle scale (Bergantzet al. , 2017). Such hydrogranular behavior leads to local energy
dissipation and phase segregation such that the final state of the
mixture cannot be predicted even if the initial conditions are
constrained (Bergantz et al. , 2017, Philpotts et al. ,
1998, Qin & Suckale, 2020, Schleicher & Bergantz, 2017). Numerical
approaches to modeling magma mushes as granular media have been pursued
by studies including Bergantz et al. (2017), who developed
granular models capable of capturing such complex particle-particle
behavior in magma mushes. However, one of the challenges for such models
includes upscaling results to the magmatic (spatial and temporal) scale.
2 Derivation of a physics-based forward model
To explore the issues outlined above, we develop a numerical model of
compaction and apply it first to the phase separation experiments of
Hoyos et al. (2022). Hoyos et al. (2022) performed a
series of analog “French Press” experiments on monodisperse (and in
some cases, bi-disperse) particles immersed in corn syrup (Fig.
2a ). In these experiments, the bottom boundary of the experimental
domain migrates upwards at a constant boundary velocity,\(\mathbf{v}_{\mathbf{h}}\), of 0.3 mm/min resulting in an applied force
on the piston of the syringe (Fig. 2a ) and residual liquid
being extracted. A full summary of the symbols and definitions used is
provided in table 1 . The experimental setup is such that the
average porosity in the suspensions, the displacement of the piston, and
the applied force, are all recorded over the duration of the
experiments. The experiments were performed on monodisperse particles
shape distributions with aspect ratios of 1:1, 2:1, and 4:1. Only
selected load curves are included in the main text of the manuscript,
however, the load data for all the experiments can be found in the
supplementary material.
Table 1 – Symbols and definitions.