Coupled effects of cooling history, growth kinetics, and compositional convection on magma mush solidification

Compositional convection is one of the primary physical processes responsible for redistributing solute during the solidification of crystal mushes from multicomponent melts, a phenomenon frequently encountered in geological fluid mechanics, in particular during the cooling of magma intrusions. The key factor controlling solidification is the rate of cooling through contact with the surroundings. In this study, we focus on understanding the interplay between the cooling history, compositional convection, and the growth of a crystal mush driven by local supercooling. We analyze a mathematical model that describes the growth of the mushy region cooled from below, bounded from above by a melt region of finite volume. The melt region is assumed to have a well-mixed composition as a result of compositional convection. Contrary to initial expectations, we found that increasing the rate of bottom cooling does not necessarily result in a thinner mush with a higher solid fraction. Instead, the response depends on the kinetic law governing the mush growth rate as a function of local supercooling. Our results contribute to the current open debate within the volcanological and petrological communities about the effects of compositional convection on magma crystallization.