Magma dynamics and cooling in sub-volcanic intrusions: insights on eruption potential from finite element modelling

Abstract The emplacement of high-viscosity magma at shallow crustal levels involves a risk for volcanic eruptions but may also produce accessible heat sources for geothermal exploration. Assessing the volcanic risk and the geothermal potential of newly forming and existing sub-volcanic intrusions requires an understanding of their growth and subsequent cooling dynamics. As these processes cannot be directly observed in nature, modelling can deliver useful insights. Here, we present a series of finite element method (FEM) models that simulate the dynamics of magma movement and cooling during the formation of a shallow cryptodome inflating from a sill. The melt and solid volume fraction and temperature-dependent physical properties of the crystallizing magma are determined by simulations conducted with the Rhyolite-MELTS code. The results of the FEM models allow us to investigate the role of magma influx rate on the fluid dynamics and magma cooling inside the intrusion during and after magma influx. We conclude that magma inflow dynamics governs the volume and distribution of eruptible magma, as well as the duration for which the magma remains sufficiently hot to either be remobilized for an eruption or used as heat source for geothermal energy production. These results advance our understanding of the hidden processes that occur in growing and cooling sub-volcanic intrusions in nature.