Volatile bubble growth in a decompressing magmatic system: A many‐bubble model

Abstract

Recently, a new model of volatile bubble growth in magma with coupling to the melt advection field was proposed. In that model, the competitive effects of the other (randomly located) bubbles on the growth dynamics were treated in a mean‐field sense. That model predicts the possibility of dynamical transitions to or from inflationary regimes, whereby the growth rate and the average bubble radius increase rapidly. We present here numerical results pertaining to a decompressing magma, in which the fluid pressure explicitly decreases at a constant rate, thus simulating the ascent of the magma from a state of low volatile supersaturation. It is seen that, as the supersaturation increases (due to decompression), the system may undergo a transition to an inflationary regime, leading to a sudden increase in vesicularity. The numerical results show that the system dynamics may exhibit an oscillatory behavior characterized by a decompression‐induced succession of transitions to and from inflationary regimes. The model also shows that a constant bubble growth rate solution exists for intermediate times. This feature is in agreement with some experimental observations reported in the literature.