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| Blanc, G; Boulegue, J; Gieskes, Jm. |
| We report here our findings on the chemistry of methane, manganese and chloride dissolved in the interstitial water of the Barbados accretionary complex. The decollement separating the subduction plate from the accretionary wedge is geochemically characterized by high methane and manganese and low chloride concentrations relative to buried seawater. Sandstone layers occurring below the decollement and the compressive structures recording some of the earliest effects of offscraping are also characterized by similar anomalies. A fluid with the same characteristics is also found six kilometres to the east of the deformation front within the oceanic plate. High manganese concentration and low chlorinity also occur in the pore water of the offscraped sediment... |
| Tipo: Text |
Palavras-chave: BARBADOS ACCRETIONARY COMPLEX; INTERSTITIAL WATER; CHEMICAL COMPOSITION; ADVECTION; DIAGENESIS. |
| Ano: 1991 |
URL: http://archimer.ifremer.fr/doc/00101/21262/18873.pdf |
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| Blanc, G; Doussan, C; Thomas, C; Boulegue, J. |
| We present a non-steady-state diffusion and advection model that describes the distribution of methane, manganese and silica concentrations versus depth at sites 671, 676, and 672 of ODP Leg 110 through an oceanic sedimentary pile undergoing horizontal shortening by means of thrust-faults and folds. The model suggests that the distribution of these chemical components above and below fluid flow conduits is controlled by molecular diffusion. Upward fluid advection from the pathways to the surrounding sediments appears to be without significance for this environment (about 1.10(-11) m.s-1, i.e. almost-equal-to 0.3 mm.yr-1). Estimates of the time necessary to produce the diffusion profiles indicate that average ages of the chemical anomalies increase from... |
| Tipo: Text |
Palavras-chave: NUMERICAL MODEL; INTERSTITIAL WATER; DIFFUSION; ADVECTION; DIAGENESIS. |
| Ano: 1993 |
URL: http://archimer.ifremer.fr/doc/00100/21137/18757.pdf |
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| Pougnet, F.; Blanc, G; Mulamba-guilhemat, E.; Coynel, A.; Gil-diaz, T.; Bossy, C.; Strady, E.; Schäfer, J.. |
| Despite major management efforts initiated in 1987 and 2007 and decreasing emissions in the Gironde watershed, cadmium (Cd) levels in oysters from the downstream Gironde estuary are still higher to the consumption limit (5 mg/kg, dw, EC). Dissolved Cd concentrations were measured in surface water collected in the Gironde estuary during nine cruises (2014 – 2015). The obtained theoretical (Cdd0) concentrations and the daily net Cdd fluxes, using the Boyle’s method, confirm a decadal stepping decrease of the Cd pollution corresponding to that observed in the oysters from the long term national monitoring for priority contaminants at the estuary mouth. As this observation invalidates the previous estimating methods for estimating annual net Cdd fluxes, we... |
| Tipo: Text |
Palavras-chave: Estuaire; Cadmium dissous; Modélisation; Flux nets; Estuary; Dissolved cadmium; Computation; Net fluxes. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00485/59713/62808.pdf |
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| Vitali, F; Blanc, G; Larque, P; Samuel, J. |
| The sedimentary sequence recovered at Site 840 ODP in the Tonga Platform is 597 m thick and ranges in age from Holocene to late Miocene. Here, from the 49 samples analysed, three classes of sediments can be identified, based on their proportion of biogenic carbonate and volcanogenic content. These three classes are comparable with those previously differentiated in the Lau Basin (Sites 834-839) and with some sediments from the Tonga Trench Margin (Site 841). In constrast with neighbouring Site 834-839 sediments from the Lau Basin, the Site 840 sediment composition appears to be exempt of hydrothermal pending material and seems to be characterized only by biogenic and terrigenous andesiticrhyolitic volcanic inputs. The alteration of volcanic material... |
| Tipo: Text |
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| Ano: 1994 |
URL: http://archimer.ifremer.fr/doc/00099/21032/18658.pdf |
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| Anschutz, P; Blanc, G. |
| The 23,000 year old sediments of the Atlantis II Deep rest on a basaltic substratum and are overlaid by a dense and hot brine pool. The facies of the lower sequence of the West basin consists essentially of bioclastic and detrital particles (DOP facies). The primary calcite and aragonite of planktonic tests of the DOP facies have been transformed into Ca-, Mg-, Mn-, and Fe-carbonate solid solutions. Pyrite amounts to about 1-2% (wt) at the bottom of the sedimentary series, and as much as 20% (wt) in the upper part of the sequence. These high iron - and manganese - earing minerals are the product of early diagenetic processes in an environment favourable to bacterial activity, to which biogenic and detrital particles, organic matter, and iron and manganese... |
| Tipo: Text |
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| Ano: 1995 |
URL: http://archimer.ifremer.fr/doc/00097/20863/18481.pdf |
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