The role of water in the 1944 Vesuvius eruption |
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| Authors: | Daniela Dolfi Raffaello Trigila |
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| Institution: | 1. Istituto di Mineralogia e Petrografia, Università di Roma, Italy
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| 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: - CaMgSi2O6(liq) = CaMgSi2O6(cpx)
- NaAlSi3O8 (liq) = NaAlSi3O8 (plag)
- CaAl2Si2O8 (plag)=CaAl2SiO6(cpx)+SiO2(liq) have been established for three intracrustal crystallisation stages: I) 8.0 kbar and 1255 °C; II) 4.0 kbar and 1178 °C; III) 0.5 kbar and 1105 °C.
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. |
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