Pressurization vs. flushing in the modelling of volcanic gases at basaltic volcanoes

When modelling the composition of chemical gases released at basaltic volcanoes, two end-member processes can be quantitatively constrained by means of thermochemical techniques: closed-system magma degassing or, alternatively, the ascent of gas-bubbles, separated from the reservoir melt at some depth and flushing through the surrounding melt up to surface. In the first scenario, the ascent of volatile-rich (bubbles+melt) magmas from the reservoir is followed by gas/melt separation and fast ascent of the gas phase without any further re-equilibration with the residual melt filling the shallower conduit system. The features of this mechanism must be realized within the lumped approximation i…