Consulta: subjectFacets:"Helium isotopes"
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Data/hora: 12/06/2024 05:36:20

Helium isotopes on the Pacific-Antarctic ridge (52.5°–41.5°S)
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Moreira, M; Dosso, Laure; Ondreas, Helene.
The first isotopic data and concentrations of helium are reported for the Pacific-Antarctic ridge between 52.5 degrees S and 41.5 degrees S. The He-4/He-3 ratio is extremely homogeneous over more than 1200 km, with a mean ratio of 99,275 (R/Ra = 7.29) and a standard deviation of 2719 (0.19), which is the lowest dispersion observed for the global mid oceanic ridge system. Moreover, the Menard T. F. is a frontier between two mantles with slightly different helium isotopic ratios (96,595 +/- 1520 and 100,347 +/- 2330). No difference in the helium concentration between the two ridge segments defined by the Menard T. F. can be observed, as well as no significant difference in the U and Th contents suggesting that the difference in helium isotopic ratio is old...
Tipo: Text
Palavras-chave: Pacific Antarctic ridge; Mantle geochemistry; Helium isotopes.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-4348.pdf

Distribution and behavior of dissolved hydrogen sulfide in hydrothermal plumes
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Radford Knoery, Joel; German, C; Charlou, Jean-luc; Donval, Jean-pierre; Fouquet, Yves.
Through the deep ocean, hydrothermal plumes disperse high concentrations of key chemical tracers including He-3, CH4, Mn, Fe, H2S, etc. This paper focuses on the distribution and behavior of total dissolved sulfide (sulfide hereafter) in hydrothermal plumes to show that its plume concentration decreases to subnanomolar a few kilometers from the vents. We also report on sulfide removal rates determined at in situ conditions; we observe that they are two orders of magnitude greater than for open ocean seawater, consistent with sulfide being detected only in the vicinity of hydrothermal vents. From our observations, we infer that the sole presence of sulfide in hydrothermal plumes locates active venting at the kilometer scale.
Tipo: Text
Palavras-chave: Chemical oceanography; Mid ocean ridges; Metals; Helium isotopes; Methane; Tracers; Hydrogen sulphide; Plumes; Hydrothermal activity.
Ano: 2001
URL: https://archimer.ifremer.fr/doc/2001/publication-688.pdf

Helium isotopic composition of hydrothermal fluids from the Manus back-arc Basin, Papua New Guinea
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Fourre, E; Jean Baptiste, P; Charlou, Jean-luc; Donval, Jean-pierre; Ishibashi, J.
We present isotopic analysis of helium in hydrothermal fluids from the Manus back-arc basin, collected during the French-Japanese Manusflux and Manaute cruises in 1995 and 2000, respectively. The helium isotope composition of the fluids is comparable to that measured elsewhere in similar subduction environments, with He-3/He-4 values (7.4 to 7.9 R-a) slightly lower than typical MORB values, except on the Manus Spreading Center (MSC) where higher values (12 +/- 0.1 R-a) are observed. The causal link between the narrow spatial extent of the He-3/He-4 anomaly at the MSC and a He-3-rich deep mantle component remains elusive, based on available geophysical data. Thus, the Manus Spreading Center results may be an interesting example of small scale upper-mantle...
Tipo: Text
Palavras-chave: Western Pacific; Manus Basin; Back arc basins; Hydrothermal fluids; Helium isotopes.
Ano: 2006
URL: http://archimer.ifremer.fr/doc/2006/publication-4203.pdf