Gas Hydrate-Associated Carbonates and Methane-Venting at Hydrate Ridge: Classification, Distribution, and Origin of Authigenic Lithologies

Greinert, Jens; Bohrmann, Gerhard; Suess, Erwin

doi:10.1029/gm124p0099

Cited by 178 publications

(239 citation statements)

References 23 publications

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“…Almost all modern marine environments with gas hydrates develop seep carbonates [44][45][46][47]. This phenomenon mirrors the close relationship between gas hydrates and seep carbonates.…”

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confidence: 94%

First discovery and characterizations of late Cretaceous seep carbonates from Xigaze in Tibet, China

Tong

Chen

2012

Chin. Sci. Bull.

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Hydrocarbon seeps, widely occurring in continental margins, have become increasingly focused owing to their close relationships with gas hydrates, strong greenhouse gas methane, and biological resources in extreme environments. Ancient hydrocarbon seeps have already been recognized from Devonian to Quaternary strata worldwide based on seep carbonates or seep-related fossil chemosynthetic assemblages. However, seep-related deposits are rarely found from ancient strata in the mainland China. Here, we report the first discovery of an ancient seep deposit, specifically late Cretaceous seep carbonates from Xigaze in Tibet, China. Xigaze seep carbonates, occurring as nodules, are enclosed in upper Cretaceous turbidite strata in Xigaze forearc basin. These carbonates are composed of authigenic carbonate (56.2% on average), clastic quartz and feldspar (27.3% on average), and clay minerals (chlorite, illite and smectite, 16.5% on average). Clotted micrites, peloids and framboid pyrites are frequently observed, all of which are common in modern seep carbonates. The carbonates have negative  13 C values varying from 27.7‰ to 4.0‰ (V-PDB), suggesting that thermogenic methane is the primary carbon source. Ce/Ce* values revised by eliminating La effects show no real Ce anomaly, indicating the carbonates were primarily precipitated in a weak reducing environment. Overall, these features provide unequivocal evidences that the seafloor of Xigaze forearc basin developed hydrocarbon seeps in late Cretaceous. seep carbonate, carbon isotope, sedimentary fabric, Xigaze, late Cretaceous Citation:Tong H P, Chen D F. First discovery and characterizations of late Cretaceous seep carbonates

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“…Almost all modern marine environments with gas hydrates develop seep carbonates [44][45][46][47]. This phenomenon mirrors the close relationship between gas hydrates and seep carbonates.…”

mentioning

confidence: 94%

First discovery and characterizations of late Cretaceous seep carbonates from Xigaze in Tibet, China

Tong

Chen

2012

Chin. Sci. Bull.

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“…The overall reaction of combined AOM and sulphate reduction increases alkalinity, promoting the precipitation of authigenic carbonate 12 . An estimated 14% of biologically oxidized methane at active seep settings precipitates in this manner 13 , leading to a range of carbonate minerals 14 . The resulting precipitation products may vary in size, ranging from microcrystals 15 to extensive structures of pavements, slabs and mounds produced by upward growth (known as chemoherms) or post-formation winnowing 14,16,17 .…”

mentioning

confidence: 99%

“…An estimated 14% of biologically oxidized methane at active seep settings precipitates in this manner 13 , leading to a range of carbonate minerals 14 . The resulting precipitation products may vary in size, ranging from microcrystals 15 to extensive structures of pavements, slabs and mounds produced by upward growth (known as chemoherms) or post-formation winnowing 14,16,17 . Carbonate volumes have been estimated for a few regions of active seepage and may exceed a million cubic metres at areas such as the Costa Rica margin 4 , Hydrate Ridge 6 and the Chilean subduction zone 5 , suggesting that these methane-derived structures have the potential to serve as a significant habitat within the seep ecosystem.…”

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confidence: 99%

Carbonate-hosted methanotrophy represents an unrecognized methane sink in the deep sea

et al. 2014

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The atmospheric flux of methane from the oceans is largely mitigated through microbially mediated sulphate-coupled methane oxidation, resulting in the precipitation of authigenic carbonates. Deep-sea carbonates are common around active and palaeo-methane seepage, and have primarily been viewed as passive recorders of methane oxidation; their role as active and unique microbial habitats capable of continued methane consumption has not been examined. Here we show that seep-associated carbonates harbour active microbial communities, serving as dynamic methane sinks. Microbial aggregate abundance within the carbonate interior exceeds that of seep sediments, and molecular diversity surveys reveal methanotrophic communities within protolithic nodules and well-lithified carbonate pavements. Aggregations of microbial cells within the carbonate matrix actively oxidize methane as indicated by stable isotope FISH-nanoSIMS experiments and 14 CH 4 radiotracer rate measurements. Carbonate-hosted methanotrophy extends the known ecological niche of these important methane consumers and represents a previously unrecognized methane sink that warrants consideration in global methane budgets.

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“…Nevertheless, the precipitation of aragonite and calcite seems to be favored in more oxic environments with both high sulphate concentration and alkalinity. On the other hand, the crystallization of Mg-calcite and dolomite preferentially occur under slightly more anoxic conditions, with lower SO 4 2-content as well as a lower total alkalinity (Greinert et al 2001), conditions observed in freshwater lakes. The presence of manganese carbonate cement within ostracode shells would corroborate this assumption.…”

Section: Vesicles Formationmentioning

confidence: 99%

Fluid escape structures as possible indicators of past gas hydrate dissociation during the deposition of the Barremian sediments in the Recôncavo Basin, NE, Brazil

et al. 2017

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Empty elliptical vesicles are observed in outcrops of Barremian very fine clayey sandstone to siltstone lacustrine slurry deposits of the Pitanga Member (Maracangalha Formation), exposed in the Maré Island, Southern Recôncavo Basin, Brazil. These sedimentary features have been traditionally interpreted as water escape structures triggered by the diapirism of the underlying shales of the Candeias Formation. This work proposes that vesicles were generated during massive gas hydrate dissociation as a result of tectonic activity in a paleolake system. Tectonic uplift would have triggered both the reduction of the confining pressure as well as an increase in lake bottom temperature, resulting in the instability of gas hydrate and causing intense release of both methane -or carbon dioxide (CO 2 ) -and water. On one hand, this proposal has a strong impact on paleoenvironmental interpretations, giving support to the current hypothesis that rocks related to the Pitanga Member would have been deposited under water columns deep enough for gas hydrate formation and subsequent dissociation. On the other hand, it provides new insights on the genesis of fluid escape structures in sedimentary rocks, both lacustrine and marine, providing a paleobathymetric indicator.KEYWORDS: Fluidization; Gas hydrates; Maracangalha Formation; Pitanga Member; Recôncavo Basin; Vesicles. Recôn-cavo, uma RESUMO: Vesículas elípticas ocas são observadas em afloramentos de arenitos argilosos muito finos e siltitos lacustrinos do Membro Pitanga da Formação Maracangalha, expostos na Ilha de Maré, sudeste da Bacia do Recôncavo, Estado da Bahia, Brasil. Essas rochas foram depositadas em condições subaquosas e são consideradas depósitos gravitacionais do tipo slurry. Essas feições têm sido tradicionalmente interpretadas como sendo estruturas de escape de água, resultado da ação do diapismo de folhelhos sotopostos da Formação Candeias. Este trabalho propõe que as vesículas foram geradas durante uma intensa dissociação de hidratos de gás em resposta à atividade tectônica existente naquele sistema lacustre. O soerguimento tectônico do fundo do lago teria propiciado a redução da pressão confinante nos poros sedimentares, bem como o aumento de temperatura nas águas de fundo, resultando na instabilidade dos hidratos de gás contidos nas porções rasas dos sedimentos e causando uma violenta liberação de metano -ou gás carbônico (CO 2 ) -e água. Se correta, esta proposta tem um grande impacto na interpretação paleoambiental da Bacia do INTRODUCTIONDiscussions regarding the formation and dissociation of gas hydrates in oceans, seas and permafrost environments are widely described in the literature (Collett, 2002;Freire, 2010;Haacke et al., 2009;Hyndman & Davis, 1992;Matsumoto, 2005;Matsumoto et al., 2009). However, studies concerning fossil gas hydrate formation and dissociation in both marine and lacustrine environments are rare, since the evidences of such processes are not based on direct observations, as those of present day gas hydrate occurrences. ...

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Gas Hydrate-Associated Carbonates and Methane-Venting at Hydrate Ridge: Classification, Distribution, and Origin of Authigenic Lithologies

Cited by 178 publications

References 23 publications

First discovery and characterizations of late Cretaceous seep carbonates from Xigaze in Tibet, China

First discovery and characterizations of late Cretaceous seep carbonates from Xigaze in Tibet, China

Carbonate-hosted methanotrophy represents an unrecognized methane sink in the deep sea

Fluid escape structures as possible indicators of past gas hydrate dissociation during the deposition of the Barremian sediments in the Recôncavo Basin, NE, Brazil

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