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| Dekov, V.m.; Egueh, N. M.; Kamenov, G. D.; Bayon, G.; Lalonde, S.v.; Schmidt, M.; Liebetrau, V.; Munnik, F.; Fouquet, Yves; Tanimizu, M.; Awaleh, M. O.; Guirreh, I.; Le Gall, B.. |
| Carbonate chimney-like deposits up to 60 m high are scattered or arranged in rows at the shores of a desiccating hypersaline and alkaline lake from a continental rift setting (Lake Abhé, Afar Rift, Djibouti). The chimneys formed sub-aqueously in the lake water body at a higher water level than observed today. Alternating calcite and low-Mg calcite + silica concentric layers compose the chimney structures. Mineralogical and geochemical investigations of the chimneys, lake water, and hot spring (hydrothermal) fluids suggest that the chimneys are a result of rapid carbonate precipitation during the mixing of hydrothermal fluids with lake water. In contrast to the hot spring fluid, lake water is enriched in HREE and possesses a pronounced positive Ce anomaly,... |
| Tipo: Text |
Palavras-chave: Carbonate; Chimney; Continental rift; H-C-O-Ca-Sr-Nd-Pb-Th-U-isotopes; Hydrothermalism. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00206/31762/30172.pdf |
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| Dekov, V. M.; Lalonde, Stefan; Kamenov, G. D.; Bayon, Germain; Shanks, W. C., Iii; Fortin, D.; Fouquet, Yves; Moscati, R. J.. |
| An inactive vent field comprised of dead chimneys was discovered on the ultrafast East Pacific Rise (EPR) at 18°S during the research campaign NAUDUR with the R/V Le Nadir in December 1993. One of these chimneys was sampled, studied and found to be largely composed of silica-mineralized bacterial-like filaments. The filaments are inferred to be the result of microbial activity leading to silica (± Fe-oxyhydroxide) precipitation. The chimney grew from the most external layer (precipitated 226 ± 4 yr. B.P.) towards the central chimney conduit. Hydrothermal activity ceased 154 ± 13 yr. B.P. and the chimney conduit was completely sealed. Mixing between an end-member hydrothermal fluid and seawater explains the Sr–Nd isotopic composition of the chimney.... |
| Tipo: Text |
Palavras-chave: Chimney; C-O-Si-Sr-Nd-Pb-Th-U isotopes; Hydrothermal; Seafloor; Silica. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00280/39143/37698.pdf |
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