Energy budget during magma ascent: using viscous fluid-filled crack in laboratory models to investigate magmatic dike intrusions in natural settings

Dikes play a significant role in transporting magma from the Earth's depth to the surface. Likewise, dikes constitute a network of intrusions connected to storage bodies that form the volcanic plumbing system promoting magma transport beneath and inside active volcanic centers, channeling its ascent during volcanic eruptions.

Characterizing the dike properties is critical for determining whether a dike will reach the surface and estimating the time it needs to do so. Increasing our understanding of diking could contribute to assessing the volcanic hazard.

We implement laboratory models by means of viscous-oil injections in solidified gelatin to study the dynamic properties of magmatic dikes propagating in the upper crust. We prepare gelatin at 1.5 wt.% gel and 15 wt.% salt to produce a host medium with lower resistance to fracturing and higher density that facilitates the propagation of viscous fluids. Salty gelatin is carefully prepared following a protocol that ensures the elastic properties remain consistent over all our experiments. We inject oils 1000 and 10000 times more viscous than water from the bottom of the gelatin tank. Injection volumes range from 10 to 50 ml. Such experimental setting ensures a correct scaling of magma buoyancy and viscosity to study dike dynamics. A camera facing the models follows the vertical trajectory of the dike. The second camera positioned above the models records the opening and width of the crack just before the eruption.

From camera data recorded for a large set of experiments, we constrain the propagation velocity for different dike volumes. We implemented these experiments to study fluid-filled crack velocity and velocity variations as a function of fluid volume, buoyancy, viscosity, and gelatin fracture toughness. We simulate the laboratory experiments using a numerical model for dike propagation to address fundamental questions about the total energy budget involved in the fluid-filled fracture propagation process. Here we present preliminary results concerning the energy budget, in particular, comparing the energy needed to extend the brittle fracture with respect to the energy dissipated by the viscous fluid motion and better characterizing the propagation regime of the experiments versus magmatic dikes.

We foresee the application of these models to caldera settings, focusing on Campi Flegrei, Italy.