Fluid and Melt Inclusions from Subvolcanic to Surface Environment in the Campi Flegrei (Napoli, Italy) Active Volcanic System

Abstract

ABSTRACT We present a summary of the results obtained on more than 25 years of research achieved on Campi Flegrei (CF) past eruptions, focusing our attention on the role played by fluids in the magmatic system based on fluid (FI) and melt inclusions (MI). Particularly FI and MI data from subvolcanic igneous systems in the CF area provide valuable information on the nature of fluid and melt phases trapped during the late evolutionary stages of the alkaline magmatic systems. They also document liquid immiscibility at pre-eruptive magma conditions and furnish evidence of high salinity fluids (brines) exsolving directly from magma in the upper part of the plumbing system at the magmatic/hydrothermal transition and playing critical roles in ore metal transport. CF volcanic system can be interpreted as representing a modern analogue of low sulfidation epithermal deposits or a porphyry copper system. This interpretation led to the formulation of a model to explain ground movements (bradyseism) in the CF. Finally new finding for the estimations of pre-eruptive volatile contents in CF through MI are discussed. MI are the only direct samples to measure volatile contents of undegassed melt at sub-volcanic conditions. Since the depth of formation of MI is estimated using H2O-CO2-silicate melt solubility models, it is important to emphasize that, to obtain a more accurate measure of the pre-eruptive CO2 concentration, not only the CO2 in the glass but also in the bubble have to be measured otherwise the minimum CO2 content in MI is obtained.