Genesis and evolution of the fumaroles of vulcano (Aeolian Islands,Italy): a geochemical model |
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| Authors: | M Carapezza P M Nuccio M Valenza |
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| Institution: | 1. Istituto di Mineralogia, Petrografia e Geochimica, Università Palermo, Italy
2. Istituto di Geochimica dei Fluidi, CNR, Palermo, Italy
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| Abstract: | A geochemical model explaining the presence of fumaroles having different gas composition and temperature at the top of the crater and along the northeastern coast of Vulcano island is proposed. A pressurized biphase (liquid-vapor) reservoir at the depth of about 2 km is hypothesized. Energy and mass balance sheets controlP-T conditions in the system.P-T must vary along a boiling curve of brine as liquid is present. The CO2 content in the steam is governed by the thermodynamic properties of the fluids in the H2-NaCl-CO2 system. On the assumption that oxygen fugacity in the system is between the HM-FMQ oxygen buffers, observed SO2/H2S, CO2/CO, CO/CH4 ratios in the fumarolic gases at the Fossa crater appear in equilibrium with a temperature higher than that observed, such as may exist at depth. The more reduced gas phases present on the sea-side may result from re-equilibrium processes in shallower aquifers. The suggested model would help in monitoring changes in volcanic activity by analyzing fumarolic gases. |
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