Massive vein-filling gas hydrate: relation to ongoing gas migration from the deep subsurface in the Gulf of Mexico

Sassen, Roger; Losh, Steven; Cathles, L. M.; Roberts, Harry H.; Whelan, Jean K.; Milkov, Alexei V.; Sweet, Stephen T.; DeFreitas, Debra A.

doi:10.1016/s0264-8172(01)00014-9

Cited by 148 publications

(92 citation statements)

References 28 publications

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“…Propane and butane are gaseous under normal standard temperature and pressure conditions, and liquid at low temperatures (at 0.1 MPa, the boiling point of propane is À 42 1C and that of butane À 0.5 1C) or at high pressure (at 20 1C, X0.75 MPa for propane, and X0.22 MPa for butane) (Schwarzenbach et al, 2003). In places where plate tectonics causes fracturing in the crust, gas and oil from deep-seated reservoirs are able to migrate upwards through the sediment as free gas or as dissolved components of geothermal fluids (Hovland et al, 1993;Sassen et al, 2001). Propane and butane are moderately soluble in water (saturation at 20 1C, 1.76 mM propane, 1.46 mM butane), with solubility increasing at lower temperatures and higher pressures (Dean, 1992;Chapoy et al, 2004), conditions often prevailing at deep-sea environments.…”

Section: Introductionmentioning

confidence: 99%

Anaerobic degradation of propane and butane by sulfate-reducing bacteria enriched from marine hydrocarbon cold seeps

et al. 2012

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The short-chain, non-methane hydrocarbons propane and butane can contribute significantly to the carbon and sulfur cycles in marine environments affected by oil or natural gas seepage. In the present study, we enriched and identified novel propane and butane-degrading sulfate reducers from marine oil and gas cold seeps in the Gulf of Mexico and Hydrate Ridge. The enrichment cultures obtained were able to degrade simultaneously propane and butane, but not other gaseous alkanes. They were cold-adapted, showing highest sulfate-reduction rates between 16 and 20 1C. Analysis of 16S rRNA gene libraries, followed by whole-cell hybridizations with sequence-specific oligonucleotide probes showed that each enrichment culture was dominated by a unique phylotype affiliated with the Desulfosarcina-Desulfococcus cluster within the Deltaproteobacteria. These phylotypes formed a distinct phylogenetic cluster of propane and butane degraders, including sequences from environments associated with hydrocarbon seeps. Incubations with 13 C-labeled substrates, hybridizations with sequence-specific probes and nanoSIMS analyses showed that cells of the dominant phylotypes were the first to become enriched in 13 C, demonstrating that they were directly involved in hydrocarbon degradation. Furthermore, using the nanoSIMS data, carbon assimilation rates were calculated for the dominant cells in each enrichment culture.

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Section: Introductionmentioning

confidence: 99%

Anaerobic degradation of propane and butane by sulfate-reducing bacteria enriched from marine hydrocarbon cold seeps

et al. 2012

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“…Structural hydrate deposits can be more concentrated than stratigraphic, and closer to sea floor, making them potentially more responsive to climate warming. Hydrates in the Gulf of Mexico and Hydrate Ridge, for example, are heavily impacted by subsurface gas migration (18)(19)(20).…”

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Ocean methane hydrates as a slow tipping point in the global carbon cycle

Archer

Buffett

Brovkin

2009

Proc. Natl. Acad. Sci. U.S.A.

344

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We present a model of the global methane inventory as hydrate and bubbles below the sea floor. The model predicts the inventory of CH 4 in the ocean today to be Ϸ1600 -2,000 Pg of C. Most of the hydrate in the model is in the Pacific, in large part because lower oxygen levels enhance the preservation of organic carbon. Because the oxygen concentration today may be different from the longterm average, the sensitivity of the model to O2 is a source of uncertainty in predicting hydrate inventories. Cold water column temperatures in the high latitudes lead to buildup of hydrates in the Arctic and Antarctic at shallower depths than is possible in low latitudes. A critical bubble volume fraction threshold has been proposed as a critical threshold at which gas migrates all through the sediment column. Our model lacks many factors that lead to heterogeneity in the real hydrate reservoir in the ocean, such as preferential hydrate formation in sandy sediments and subsurface gas migration, and is therefore conservative in its prediction of releasable methane, finding only 35 Pg of C released after 3°C of uniform warming by using a 10% critical bubble volume. If 2.5% bubble volume is taken as critical, then 940 Pg of C might escape in response to 3°C warming. This hydrate model embedded into a global climate model predicts Ϸ0.4 -0.5°C additional warming from the hydrate response to fossil fuel CO 2 release, initially because of methane, but persisting through the 10-kyr duration of the simulations because of the CO 2 oxidation product of methane.clathrate ͉ climate

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“…Cold seeps are frequently observed in marine settings of continental margins worldwide, and the last 30 years' investigations show that they are known from the tropics to the poles, in shallow shelf to hadal depths [1][2][3][4][5][6][7][8][9][10][11]. The seep fluids are commonly composed of water and methane, and occasionally heavy hydrocarbons, such as crude oil.…”

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confidence: 99%

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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Massive vein-filling gas hydrate: relation to ongoing gas migration from the deep subsurface in the Gulf of Mexico

Cited by 148 publications

References 28 publications

Anaerobic degradation of propane and butane by sulfate-reducing bacteria enriched from marine hydrocarbon cold seeps

Anaerobic degradation of propane and butane by sulfate-reducing bacteria enriched from marine hydrocarbon cold seeps

Ocean methane hydrates as a slow tipping point in the global carbon cycle

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

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