Channels or waves: controls on the reaction infiltration instability in the upper mantle

The reaction-infiltration instability has been identified as an important mechanism responsible for the formation of high-porosity melt channels in the upper mantle. To better understand this mechanism, we perform linear stability analysis and nonlinear numerical simulations in a compacting, chemically reactive porous medium. Strong interactions between compaction and reaction lead to two distinct unstable features: (1) high-porosity channels and (2) compaction-dissolution waves. Here we present a regime diagram to show that, compared to high-porosity channels, compaction-dissolution waves are favoured in systems with lower reaction rate, lower compaction viscosity (i.e. more easily compactible medium) and smaller solubility gradients. This regime diagram predicted by linear stability analysis shows good agreement with the nonlinear numerical simulations. Under geologically relevant conditions, both high-porosity channels and compaction-dissolution waves may form in the mantle, although channels are more commonly expected.