HR: 14:55h
AN: V53E-06    [Abstracts]
TI: Abundance, degassing and chemistry of halogens at Kilauea Volcano
AU: * Edmonds, M
EM: medm06@esc.cam.ac.uk
AF: University of Cambridge, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, United Kingdom
AB: The source concentration of halogens in the mantle, as well as other volatiles, is heterogeneous and related to tectonic setting. Intra-plate magmas, which give rise to ocean island basalts and are derived from a mantle plume source, are typically enriched in halogens relative to mid-oceanic ridge basalts but depleted relative to arc magmas. Fourier Transform Infra Red (FTIR) spectroscopy measurements of volcanic gases were supplemented with electron microprobe analyses of glasses in erupted products from Kilauea Volcano, Hawaii, to provide the first detailed picture of the abundance, degassing and plume chemistry of halogens at this volcano. This study reveals that typical fluxes of both HCl and HF are 50-100 t/d; Cl/S ranges from 0.01 to 0.07 and F/S from 0.01 to 0.05. SiF₄ and HBr are below detection. The abundance of halogens in melt inclusions and matrix glasses in the lavas allow formulation of their degassing path prior to eruption. Kilauea volcanic gases have lower Cl/S than volcanoes in arc settings, but are similar to those measured at other volcanoes in plume settings. F/S, on the other hand, is within range of that measured at Soufriere Hills, Masaya and Etna, indicating that there is a higher degree of homogeneity in the mantle distribution of F. The relative proportion of Cl, F and S in the volcanic plume varies considerably over time and space. This variability may be due to a number of factors: the depth of vapour-melt separation in the conduit; the degree of degassing of shallow, stagnant magma (S-rich gases exsolve first); interaction between vapour and a hydrothermal system; the relative rates of diffusion between the species; or processes occurring in the plume such as adsorption of or reaction between acidic gases and silicate particles.
DE: 8410 Geochemical modeling (1009, 3610)
DE: 8415 Intra-plate processes (1033, 3615)
DE: 8419 Volcano monitoring (7280)
DE: 8430 Volcanic gases
DE: 8439 Physics and chemistry of magma bodies
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting