A new method for quantitative analysis of helium isotopes in sediment pore‐waters

Chaduteau, Carine; Fourré, Élise; Jean‐Baptiste, Philippe; Dapoigny, Arnaud; Baumier, D.; Charlou, Jean-Luc

doi:10.4319/lom.2007.5.425

Cited by 8 publications

(3 citation statements)

References 31 publications

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“…For helium concentrations, error bars are indicated in Table 1. Full details of the sampling method and analytical procedure are available in the work of Chaduteau et al [2007].…”

Section: Sampling and Methodsmentioning

confidence: 99%

“…However, in spite of the potential of this geochemistry tool, its use in pore water studies has been hampered by the difficulties in collecting good samples (i.e., without gas loss and/or contamination problems). Here we used a new sampling and extraction method which allows the quantitative analysis of helium isotopes [ Chaduteau et al , 2007].…”

Section: Introductionmentioning

confidence: 99%

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Helium transport in sediment pore fluids of the Congo‐Angola margin

Chaduteau

Jean‐Baptiste

Fourré

et al. 2009

Geochem Geophys Geosyst

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[1] During the ZaïRov2 cruise of the ZaïAngo project (1998)(1999)(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 regime (2.4 Â 10 À8 mol/m 2 /a) can favorably be compared to literature data and contrasts with the flux computed close to the pockmark center (1.9 Â 10 À7 mol/m 2 /a). Helium depth profiles turned to be more sensitive to advection rate than temperature profiles are.

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“…For helium concentrations, error bars are indicated in Table 1. Full details of the sampling method and analytical procedure are available in the work of Chaduteau et al [2007].…”

Section: Sampling and Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Helium transport in sediment pore fluids of the Congo‐Angola margin

Chaduteau

Jean‐Baptiste

Fourré

et al. 2009

Geochem Geophys Geosyst

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“…The porewater is liberated from the sediment matrix and is degassed in the extraction vessel. Chaduteau et al (2007) recently proposed an extraction method based on flushing the sediment samples with degassed water. However this method was only applied to determine the concentrations of He isotopes, requires a dedicated extraction apparatus, and is time-consuming.…”

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An improved method for the analysis of dissolved noble gases in the porewater of unconsolidated sediments

Tomonaga

Brennwald

Kipfer

2011

Limnology & Ocean Methods

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In recent years, the analysis of noble gases in meteoric waters has become a powerful tool for studying mixing dynamics in lakes, oceans, and groundwaters, and for reconstructing past climate conditions (Kipfer et al. 2002;Schlosser and Winckler 2002). Noble-gas concentrations in sediment porewater have been shown to reflect past noble-gas concentrations in the overlying water body (Brennwald et al. 2003(Brennwald et al. , 2004, and can provide information on transport and gasexchange processes within the sediment (Brennwald et al. 2005;Strassmann et al. 2005;Holzner et al. 2008).Until now, the method developed by Brennwald et al. (2003) was the only method available for the quantitative analysis of the concentrations of noble gases dissolved in the porewater of lacustrine sediments. This method was successfully used to study the noble-gas abundance in the sediments in various lakes (Brennwald et al. 2003(Brennwald et al. , 2004(Brennwald et al. , 2005Strassmann et al. 2005), and in the Black Sea (Holzner et al. 2008). Gas extraction is achieved by connecting the bulk sediment sample container to an evacuated extraction vessel. The sample container is then rapidly heated to 150°C, which results in a pressure increase in the sample container. The bulk sediment is then extruded explosively into the extraction vessel ("blowout"), and the sediment grains are dispersed over the interior surface of the extraction vessel. The porewater is liberated from the sediment matrix and is degassed in the extraction vessel. Chaduteau et al. (2007) recently proposed an extraction method based on flushing the sediment samples with degassed water. However this method was only applied to determine the concentrations of He isotopes, requires a dedicated extraction apparatus, and is time-consuming.Although the analytical protocol of Brennwald et al. (2003) AbstractWe developed a new and improved method for the extraction of dissolved noble gases from the porewater of unconsolidated lacustrine sediments. The new method relies on the separation of the porewater from the sediment matrix by centrifugation of the bulk sediment within the closed copper tubes being used as sampling containers. After centrifugation, the porewater liberated from sediment matrix is completely separated from the dewatered sediment by applying and closing a metal clamp between the two phases. After separation, the noblegas abundances are determined only in the porewater phase by applying the standard protocols used for noblegas analysis in water samples, which allows simpler, faster and more reliable measurements. The new method overcomes known experimental difficulties encountered by our former method, such as the release of He from sediment grains, and incomplete extrusion of the bulk sediment from the copper tube used as a sample container. It follows that the determination of the He concentrations and isotope ratios in the sediment porewater is less affected by He locally produced in sediment minerals. The new method is less operator-sensitive and the noble-...

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