Book Description

The study of fluid (FI) and melt inclusions (MI) can be a powerful tool for understanding melt generation, crystallization, mixing histories of magmas and the conditions of magma evolution during their ascent to the surface. FI and MI data from the alkali syenite xenoliths of different subvolcanic igneous systems in the Neapolitan volcanic area (Vesuvius, Campi Flegrei, Ponza and Ventotene) in Italy provide valuable information on the nature of fluid and melt phases trapped during the late evolutionary stages of these alkaline magmatic systems. They also document liquid immiscibility at pre-eruptive magma conditions and furnish evidence that high salinity fluids (brines) exsolve directly from magma in the upper part of chambers at the magmatic/hydrothermal transition and play critical roles in ore metal transport. Magma chamber margins are of particular significance because FI and MI may record the various evolutionary processes during the crystallization of the magmatic system. The complex daughter crystal assemblages seen in the silicate melt + CO2 + H2O and silicate melt, hypersaline or S-rich aqueous inclusions found in xenoliths of some samples record high solute contents in the fluid(s) during entrapment and provide direct evidence of the magmatic source of these metals. The latter inclusions could be of considerable interest for the interpretation of ore genesis, because FI and MI demonstrate a linkage of these systems with low sulfidation epithermal deposits and some porphyry systems. In addition, FI and MI data are used to address the problem of frequent ground movements (bradyseism) in the Campi Flegrei, interpreted as representing a modern analog behaving physically like a porphyry system.