HR: 15:10h
AN: V33G-07    [Abstracts]
TI: Rare gas isotopic compositions in single vesicles from oceanic basalt glasses using UV laser ablation
AU: Moreira, M A
EM: moreira@ipgp.jussieu.fr
AF: IPGP, 4 place jussieu, Paris, 75005 France
AU: Lecomte, A
EM: lecomte@ipgp.jussieu.fr
AF: IPGP, 4 place jussieu, Paris, 75005 France
AU: * Allegre, C J
EM: allegre@ipgp.jussieu.fr
AF: IPGP, 4 place jussieu, Paris, 75005 France
AB: A 193nm laser (ArF) was installed on the mass spectrometer ARESIBO II in order to analyze single vesicles in oceanic basalt glasses. Pieces of 1/2 cm in size of glasses (MORB and OIB) were loaded in a cell under vacuum, connected to the purification and extraction line. After purification, rare gases were introduced in the mass spectrometer for analyze with the standard procedure. Measurement of the CO2 abundance was performed using a MKS Baratron before gas purification, by assuming that the gas in MORB vesicles is mainly CO2. We want to address three issues. One is the origin of the atmospheric component observed in some oceanic basalts, that is similar to modern air for both isotopic and elemental ratios. The second is to constrain the vesiculation process when the magma is en route to the surface as well the nature of the degassing (e.g. distillation vs. closed system vesiculation depending of the tectonic context). The last issue is to constrain the mixing process between MORB and OIB magmas when a hotspot is located on the ridge (e.g. Shona and Discovery ridge anomalies in the south atlantic). The preliminary results show important variations for the isotopic ratios and gas abundances in the vesicles of a single sample, suggesting that the air component is located in vesicles, associated with mantle derived helium and CO2.
DE: 1025 Composition of the mantle
DE: 1040 Isotopic composition/chemistry
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting