Reactive melt channelization in an upwelling mantle

Partial melting occurs in the upwelling mantle due to adiabatic decompression, and melt is thought to be transported through a channelized network formed by reaction-infiltration instability. Earlier studies of melt channelization primarily focused on melt transport while neglecting the melt production process, whereas recent models that incorporate decompression melting argue that adiabatic melting stabilizes reactive flow and suppresses channel formation. Therefore, how reactive flow interacts with decompression melting remains poorly understood for the mantle melt transport problem.

To better understand this problem, we present a two-phase flow model in an upwelling, compacting, and chemically reactive medium, based on conservation of mass, momentum, and composition for a solid-melt system. The mass transfer rate from solid to melt includes contributions from both chemical reaction and adiabatic decompression melting. Using this framework, we first derive a vertical, one-dimensional steady-state melting model. We then introduce small perturbations to this base state and perform two-dimensional, time-dependent simulations. The results demonstrate that significant melt channelization can occur in the presence of melting driven by adiabatic decompression.

We further explore the evolution of magmatic channels across parameter space and identify the key controls on this behaviour. In particular, we find that the porosity-dependent bulk viscosity, which controls the solid compaction, is a key stabilizing mechanism in the system. We analyse the balance between reactive melting and compaction associated with decompression melting, and explore the parameter regime under which melt channelization may occur in the mid-ocean ridge system dominated by decompression melting.