HR: 0830h
AN: V21C-0537    [PDF]
TI: CO$_{2}$ budget from active volcanoes of central Mediterranean: preliminary estimate for Ischia Island (Italy).
AU: * Pecoraino, G
EM: pecorain@pa.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Palermo, Via Ugo La Malfa 153, Palermo, I-90146 Italy
AU: Brusca, L
EM: brusca@pa.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Palermo, Via Ugo La Malfa 153, Palermo, I-90146 Italy
AU: D'Alessandro, W
EM: walter@pa.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Palermo, Via Ugo La Malfa 153, Palermo, I-90146 Italy
AU: Giammanco, S
EM: giamm@pa.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Palermo, Via Ugo La Malfa 153, Palermo, I-90146 Italy
AU: Inguaggiato, S
EM: inguagg@pa.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Palermo, Via Ugo La Malfa 153, Palermo, I-90146 Italy
AU: Longo, M
EM: longo@pa.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Palermo, Via Ugo La Malfa 153, Palermo, I-90146 Italy
AB: Ischia Island (46 km$^{2}$) is an active volcano located a few kilometres northwest of the bay of Naples (Central Italy). It last erupted in 1302 A.D. and its activity is currently characterised only by low-temperature ($T\deg$ max. = $100\deg$ C) gas emissions, such as fumaroles and anomalous soil degassing. A geothermal reservoir (estimated reservoir temperature near $280\deg$ C; Inguaggiato et al., 2000) is also present in the island. The emitted gases are mostly water vapour and CO$_{2}$. Also H$_{2}$ is present in appreciable amounts (up to 2.5 % v/v of dry gas), together with minor concentrations of CH$_{4}$ He and CO. Based on helium and carbon isotopic ratios (R/Ra $\sim$ 3.6; $\delta^{13}$C$_{(CO2)}$ $\sim$ -2 \permil), a magmatic source can be inferred for these gases. The present study was mainly aimed at carrying out a preliminary estimate of the total output of magmatic CO$_{2}$ from Ischia, considering all types of fluids emitted there. Soil CO$_{2}$ fluxes (measured with the accumulation chamber) gave a value of about 2.5 Mt a$^{-1}$, that is much lower than the amount estimated at Mt. Etna (13 to 25 Mt a$^{-1}$; Allard et al., 1991; D'Alessandro et al., 1997), but more than an order of magnitude higher than that estimated at Pantelleria Island and at Vulcano (Favara et al., 2001). The amount of CO$_{2}$ dissolved into ground water as carbonatic species is only 0.025 Mt a$^{-1}$, considering an annual volume of infiltrated water of about 8 $\times 10^{6}$ m$^{3}$. The overall output of CO$_{2}$ from Ischia indicates that this island is site of active volcanic degassing and deserves a more careful volcanological monitoring.
DE: 1040 Isotopic composition/chemistry
DE: 1094 Instruments and techniques
DE: 1099 General or miscellaneous
DE: 8424 Hydrothermal systems (8135)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting