The role of water in the 1944 Vesuvius eruption

Abstract

The P-T path of magma associated with the 1944 Vesuvius eruption has been outlined on the basis of probe mineralogy and the relationships between the crystallising phases. Equilibrium P-T values, obtained from the reactions: The H2O content in the magma has been estimated from an experimental calibration of $$a_{^{CaMgSi_2 O_6 } }^{liq}$$ as a function of $$X_{H_2 O}^{liq}$$ at P tot = 2 kbar. The estimated water contents of the magma for the three stages, I) 0.7%; II) 0.9%; III) 1.1%, are consistent with the pattern of activity of the 1944 Vesuvius eruption and with the relationship between the lavas. The shallow depth of H2O-saturation of the magma, 0.24 kbar at 1100 °C, is consistent with the eruption sequence of lava flows followed by lava fountain activity.