Effects on the solubility and the volatile release from magmatic intrusions

The process of fractional crystallization within a magma body has an influence on the solubility and thus on the associated release of volatiles. Nevertheless, this mechanism is widely neglected in the literature. Due to cooling of an intrusion, nominally anhydrous minerals precipitate from the melt. These minerals mainly incorporate elements that are compatible with their crystal lattice. Since volatiles such as H₂O and CO₂ behave like incompatible elements, they accumulate in the remaining melt. At a certain point, the melt is saturated and the exsolution of the volatiles initiates. The solubility is determined by several parameters like the lithostatic and the partial pressure, the temperature and the melt composition. 
In this study, we investigate the effect of these parameters as well as the impact of fractional crystallization on the solubility and the related volatile release. We focus on the exsolution of H₂O and CO₂ from basaltic magma bodies within the lithosphere. To determine the fate of the accumulating volatiles, we compare the density of the developing liquid phase (volatiles and residual melt) with the density of the host rock. If the host rock has a higher density, the liquid phase will ascent either directly to the surface or to shallower levels of the crust. Furthermore, we take into account the possibility that hydrous minerals (e.g., amphibole) are precipitated during fractional crystallization or due to a reaction with the surrounding rock.