Authigenic rhodochrosite from a gas hydrate-bearing structure in Lake Baikal

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Marco E. Ciriotti
Messaggi: 24606
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Authigenic rhodochrosite from a gas hydrate-bearing structure in Lake Baikal

Messaggio da Marco E. Ciriotti » gio 13 set, 2018 14:39

Referenza:
▪ Krylov, A.A., Hachikubo, A., Minami, H., Pogodaeva, T.V., Zemskaya, T.I., Krzhizhanovskaya, M.G., Poort, J., Khlystov, O.M. (2018): Authigenic rhodochrosite from a gas hydrate-bearing structure in Lake Baikal. International Journal of Earth Sciences, 107, 2011–2022.

Abstract:
Early diagenetic carbonates are rare in Lake Baikal. Siderite (Fe carbonate) concretions in the sediments were discovered only recently. Here, we discuss the first finding of rhodochrosite concretions (Mn carbonate) discovered in the near-bottom sediments of the gas hydrate-bearing seepage structure St. Petersburg-2 in the deep water environment of the Central Baikal Basin. The crystal lattice of rhodochrosite contains iron and calcium substituting to manganese. Based on pore water geochemistry and of δ13C values of rhodochrosite (− 23.3 and − 29.4‰), carbon dioxide (+ 3.8 to − 16.1‰) and methane (− 63.2 to − 67.8‰), we show that carbonate crystallization most likely occurred during microbial anaerobic oxidation of organic matter, and that part of the oxygen making up the rhodochrosite seems to be derived from the 18O-rich water released from dissociating gas hydrates.
Marco E. Ciriotti

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