HR: 0800h
AN: V31C-0606    [Abstracts]
TI: Experimental Constraints on Ar and Ne Solubility in H2O-CO2 Bearing Basaltic Melts
AU: Rizzo, A
EM: a.rizzo@pa.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, sezione di Palermo, via Ugo La Malfa 153, Palermo, 90146, Italy
AU: * Iacono Marziano, G
EM: g.iacono@pa.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, sezione di Palermo, via Ugo La Malfa 153, Palermo, 90146, Italy
AU: Paonita, A
EM: a.paonita@pa.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, sezione di Palermo, via Ugo La Malfa 153, Palermo, 90146, Italy
AU: Scaillet, B
EM: bscaille@cnrs-orleans.fr
AF: Institut des Sciences de la Terre d'Orléans, UMR 6113 CNRS, 1A rue de la Ferollerie, Orléans CEDEX 2, Orleans, 45071, France
AU: Gaillard, F
EM: fabrice.gaillard@cnrs-orleans.fr
AF: Institut des Sciences de la Terre d'Orléans, UMR 6113 CNRS, 1A rue de la Ferollerie, Orléans CEDEX 2, Orleans, 45071, France
AU: Nuccio, P M
EM: nucciopm@libero.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, sezione di Palermo, via Ugo La Malfa 153, Palermo, 90146, Italy
AB: Although noble gases are only trace components of magmatic volatile phases, generally dominated by H2O and CO2, they represent a powerful tool to study the degassing behavior of ascending magmas. Current models of noble gas degassing from magmas use theoretical values of noble gas solubilities, because experimental measurements in hydrous melts are very rare. Here we report an experimental study of Ar and Ne solubilities in anhydrous and H2O-CO2 bearing basaltic melts. The starting material was represented by an Etnean lava erupted in 2002. High pressure experiments were performed at superliquidus temperature (1200°C) and pressures of 1-3 kbar in internally heated pressure vessels. Investigated volatile phases were represented either by Ar or Ne (open capsule experiments) or by Ar, Ne, H2O and/or CO2 (sealed capsule experiments). In sealed capsule experiments the charged amounts of volatiles were computed to have a H2O-CO2 dominated vapor, with noble gases as minor species (partial pressure of a few bars), similarly to natural magmatic systems. Rapidly quenched glasses have been analyzed by electron microprobe (major elements), FTIR spectroscopy (H2O and CO2), bulk extraction and quadrupole mass spectrometry (noble gases). Ne and Ar molar fractions in the vapor were calculated by mass balance considering loaded and dissolved aliquots of volatiles. In some cases, the capsule was directly opened in an ultra-high-vacuum line and the pressure of each volatile was measured by a vacuometer, cryogenically separating the species. Experimental Ar solubility is comparable to the theoretical one predicted by the IP model, while Ne solubility results much higher. The effect of water on Ar and Ne solubility is in agreement with the predictions by the EIP model: increasing concentrations of dissolved water decrease the Henry's constant values for both Ar and Ne. Nonetheless, the model overestimates the intensity of the water effect on Ar solubility. The theoretical model has been therefore refitted to the experimental data. The obtained results can be directly employed for a reliable modeling of noble gas degassing from Etnean melts. The adopted experimental setting avoids any extrapolation and/or assumption deriving from the use of experimental data achieved in conditions unlike those of natural magmatic systems.
DE: 1011 Thermodynamics (0766, 3611, 8411)
DE: 3630 Experimental mineralogy and petrology
DE: 8430 Volcanic gases
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting