Variations of Cl, F, and S in Mount Etna's plume, Italy, between 1992 and 1995

Abstract

Abstract. This study investigates data on the C1, F, and S concentrations of plume-filter samples collected between 1992 and 1995 from Mount Etna. The samples were collected during eruptive and noneruptive activity and show fairly constant C1/F ratios but wide variation in the C1/S ratios. The determination of the C1/F ratio (between 5 and 14) allows an estimate of F degassing to be derived that ranges from 10 to 30% of the initial F content of the magma. The variation in the C1/S ratio fits an empirical two-stage degassing model where gas with high C1/S ratio is discharged during quiescient degassing and gas with low C1/S ratios is discharged during eruptive degassing. The typical permanent degassing occurs from a depth at which chlorine exsolution exceeds sulfur exsolution (C1/S> 1). The opposite of this behavior is observed during eruptive periods when significant sulfur degassing occurs because magma degasses at near atmospheric pressure (C1/SN0.1). The C1/S ratio in the plume, characterizing the type of degassing, has the potential to be a useful geochemical tool for monitoring the volcano.

A distinct metal fingerprint in arc volcanic emissions

“…c Emanation coefficient calculated assuming the degassing of 1100 ppm sulfur, from 1500 ppm to 400 ppm 28 and using the X/SO 2 ratio of the plume to reconstruct the concentration of element X prior to degassing. 1,29 , which causes the emanation coefficients to be anomalously high when using the X/SO 2 ratio, combined with the melt inclusion sulfur contents, to reconstruct the metal contents of the melts (main paper, figure 2). 25 .…”

BrO/SO<sub>2</sub> molar ratios from scanning DOAS measurements in the NOVAC network

“…Noguchi and Kamiya, 1963;Menyailov, 1975;Pennisi and Le Cloarec, 1998). This is due to the different solubility of volatiles in magma (e.g.…”

Radionuclide behavior in high-temperature gases from Satsuma Iwojima volcano, Japan

“…The ( 210 Bi/ 210 Pb) ratios are lower at the crater rim (23 ± 18) than in gases sampled at the end of silica tubes (68 ± 13). In the plume, the ( 210 Bi/ 210 Pb) ratios can be compared to those observed in plumes from an open conduit volcano: about 20 at Stromboli in 1996 (Gauthier et al, 2000) and about 25 at Mount Etna during the period 1976-1995(Le Cloarec and Pennisi, 2001). Higher ( 210 Bi/ 210 Pb) ratios are currently observed in fumarolic gases, and are ascribed to the decay of 210 Pb sublimates deposited along the pathway of the gases toward the surface (Le Cloarec and Gauthier, 2001).…”

“…We assume that gases emitted at 3-5 km depth from the basaltic layer do not contain significant 210 Pb,210 Bi or 210 Po, due to their very low vapor pressure at 90 MPa (Pennisi and Le Cloarec, 1998). Therefore, these radionuclides are here considered to be emitted mainly from the rhyolitic magma.…”