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Helium isotopes at the Rainbow hydrothermal site (Mid-Atlantic Ridge, 36 degrees 14 ' N) ArchiMer
Jean Baptiste, Philippe; Fourre, Elise; Charlou, Jean-luc; German, Christopher; Radford Knoery, Joel.
The He-3/He-4 ratio and helium concentration have been measured in the vent fluids and the dispersing plume of the Rainbow hydrothermal site, on the Mid-Atlantic Ridge (MAR). The He-3/He-4 ratio (7.51 R-a) and He-3 end-member concentration (25 pmol/kg) are in the range of observed values elsewhere on mid-ocean ridges, pointing to the relative homogeneity of the upper mantle with respect to helium isotope geochemistry. He-3 is linearly correlated with methane and manganese throughout the plume, with CH4/He-3 and Mn/He-3 ratios identical to those measured in the hot fluids. The bulk residence time of the plume in the rift valley estimated from the plume He-3 budget is similar to20 days. The He-3 flux transported by the plume, calculated from current-meter...
Tipo: Text Palavras-chave: Mid Atlantic Ridge; Heat flux; Isotopes; Hydrothermal vents; Helium.
Ano: 2004 URL: https://archimer.ifremer.fr/doc/2004/publication-772.pdf
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Helium transport in sediment pore fluids of the Congo-Angola margin ArchiMer
Chaduteau, Carine; Jean-baptiste, Philippe; Fourre, Elise; Charlou, Jean-luc; Donval, Jean-pierre.
During the ZaiRov2 cruise of the ZaiAngo project (1998-2000) on the passive Congo-Angola margin, several gravity cores were analyzed for helium isotopic composition of sedimentary pore waters in two cold fluid seepage zones: the Astrid slide area and the Regab giant pockmark. Gas concentration and isotopic composition are presented along with thermal data in terms of the origin and circulation of fluids. Helium isotope data lie on a mixing line between bottom seawater and an almost pure radiogenic. Helium and temperature vertical profiles are well described by the classic diffusion-advection equation. On the basis of He profiles, we estimate the advection rate on the rim of the pockmark between 1.2 and 2.3 mm/a. The He flux derived for a pure diffusive...
Tipo: Text Palavras-chave: Zaire Angola margin; Sediment; Regab; Pore fluids; Pockmark; Helium.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6112.pdf
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Gaining insight into Clipperton's lagoon hydrology using tritium ArchiMer
Jean-baptiste, Philippe; Fourre, Elise; Charlou, Jean-luc; Donval, Jean-pierre; Correge, Thierry.
Historical descriptions of the Clipperton lagoon appear to converge on the fact that it became isolated from the surrounding ocean around 1858. Since then, because of the high precipitation rate which largely exceeds evaporation in this region of the eastern tropical Pacific, a brackish lens has formed on top of the saline oceanic waters. In 1980, literature data show that the thickness of this water body was reaching 14 m. During the 2005 Etienne's Clipperton expedition, we collected lagoon water on two vertical profiles. Salinity, delta O-18 and tritium analyses were performed on these samples with the objective of gaining further insight into the lagoon hydrology and age of the deep waters. The upper 15 m were characterized by low salinities (5.4 +/-...
Tipo: Text Palavras-chave: Oxygen isotopes; Tritium; Enclosed lagoon hydrology; Clipperton atoll.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6457.pdf
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