Improved understanding of the impact of crystal mush rheology on the response of magma chambers to magmatic events is critical for better understanding crustal igneous systems with abundant crystals. In this study, we extend an earlier model by (Liao et al, 2018) which considers the mechanical response of a magma chamber with poroelastic crystal mush, by including poroviscoelastic rheology of crystal mush. We find that the coexistence of the two mechanisms of poroelastic diffusion and viscoelastic relaxation causes the magma chamber to react to a magma injection event with more complex time-dependent behaviors. Specifically, we find that the system’s short-term evolution is dominated by the poroelastic diffusion process, while its long-term evolution is dominated by the viscoelastic relaxation process. We identify two post-injection timescales that represent these two stages and examine their relation to the material properties of the system. We find that better constraints on the poroelastic diffusion time are more important for the potential interpretation of surface deformation using the model. We also find that the combination of the two mechanisms causes magma transport to reverse direction in the system, which would successively expose crystals to magma with different chemical compositions.

Saturn’s moon Enceladus has a global subsurface ocean and a porous rocky core in which water-rock reactions likely occur; it is thus regarded as a potentially habitable environment. For icy moons like Enceladus, tidal heating is considered to be the main heating mechanism, which has generally been modeled using viscoelastic solid rheologies in existing studies. Here we provide a new framework for calculating tidal heating based on a poroviscoelastic model in which the porous solid and interstitial fluid deformation are coupled. We show that the total heating rate predicted for a poroviscoelastic core is significantly larger than that predicted using a classical viscoelastic model for intermediate to large (> 10 14 Pa.s) rock viscosities. The periodic deformation of the porous rock matrix is accompanied by interstitial pore fluid flow, and the combined effects through viscous dissipation result in high heat fluxes particularly at the poles. The heat generated in the rock matrix is also enhanced due to the high compressibility of the porous matrix structure. For a sufficiently compressible core and high permeability, the total heat production can exceed 10 GW-a large fraction of the moon’s total heat budget without requiring unrealistically low solid viscosities. The partitioning of heating between rock and fluid constituents depends most sensitively on the viscosity of the rock matrix. As the core of Enceladus warms and weakens over time, pore fluid motion likely shifts from pressure-driven local oscillations to buoyancy-driven global hydrothermal convection, and the core transitions from fluid-dominated to rock-dominated heating.

Long-duration, continuous geodetic timeseries suggest that volcanoes exhibit a wide range of deformation patterns that vary between episodes of unrest. Viscoelastic deformation around crustal magma storage zones is an expected contributor to such observations, but is challenging to characterize robustly. Here we present an analytic approach for modeling crustal deformation around magma reservoirs that highlights frequency-domain signatures of viscoelastic response for temperature-dependent crustal rheology. We develop a transfer function that links frequency spectra of chamber pressure to surface displacement, finding that properties of the magmatic system are encoded at periods where geodetic observations are routinely made. Inhomogeneous viscoelastic response is characterized by a frequency-dependent elastic-viscous transition around the reservoir. We explore the consequences of this frequency dependence by examining broadband forcing consisting of multiple impulsive pressurization episodes, and identify a history dependence of volcano deformation in which past activity influences the stress state and surface deformation of future episodes.

Crustal magmatic systems likely consist of magmatic reservoirs dominated by crystal mush. Recent studies suggest that the physical processes occurring in crystal mush could alter the response of magmatic reservoirs during volcanic unrest. Here, we present a magma chamber deformation model that incorporates two new aspects in crystal mush: heat and exsolved gas. The model is based on earlier studies by Liao et. al. (2021) with additional processes including thermal-mechanical coupling, dependence of material properties on gas content, and temperature evolution following an injection of hotter magma. The post-injection time-dependent evolution of the system can be grouped into three periods, which are dominated by poroelastic diffusion (short term), viscoelastic relaxation (mid term), and thermal equilibration (long term). All three time-regimes are strongly affected by gas distribution, which alters the relative compressibility of the crystal-rich and crystal-poor regions in the chamber. The contribution of thermal evolution emerges during the mid-term evolution. The time-dependent evolution of the system highlights the intrinsic ability of a gas-bearing mushy magma chamber to generate non-monotonic time series of stresses, deformation, and magma transport.