Evolution of fumarolic gases - boundary conditions set by measured parameters: case study at Vulcano, Italy.

Autor: Mazor, E., Cioni, R., Corazza, E., Fratta, M., Magro, G., Matsuo, S., Hirabayashi, J., Shinohara, H., Martini, M., Piccardi, G., Cellini-Legittimo, P.
Zdroj: Bulletin of Volcanology; Apr1988, Vol. 50 Issue 2, p71-85, 15p
Abstrakt: Physical, chemical and isotopic parameters were measured in fumaroles at the Vulcano crater and in drowned fumaroles near the beach. The data were used to define boundary conditions for possible conceptual models of the system. Crater fumaroles: time variations of CO and SO concentrations indicate mixing of saline gas-rich water with local fresh water. Cl/Br ratios of 300- 400 favour sea-water as a major source for Cl, Brand part of the water in the fumaroles. Cl concentrations and δD values revealed, independently, amixing of 0.75 sea-water with 0.25 local freshwaterin furmarole F-5 during September 1982.Patterns of parameter correlation and mass balances reveal that CO, S, NH and B originate from sources other than sea water. The CO value of δC = − 2% favours, at least partial, origin from decomposition of sedimentary rocks rather than mantle-derived material. RadiogenicHe(1.3 × lO ccSTP/g water) and radiogenicAr(10.6 × 10 ccSTP/g water) are observed, (He/Ar) = 1.2, well in the range of values observed in geothermal systems. Drowned fumaroles: strongly bubbling gas at a pond and at the beachappears to have the same origin and initial compositionas the crater fumaroles (2 km away). The fumarolic gas is modified by depletion of the reactive gases, caused by dissolution in shallow-water. Atmospheric Ne, Ar, Kr and Xe are addeden route, some radiogenic He and Ar are maintained. The Vulcano system seems to be strongly influenced by the contribution of sea-water and decomposition of sedimentary rocks. Evidence of magmatic contributions is mainly derived from heat. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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