Gas Hydrates in Sediments of Holes 497 and 498A, Deep Sea Drilling Project Leg 67

Harrison, William; Curiale, Joseph A.

doi:10.2973/dsdp.proc.67.126.1982

Cited by 34 publications

(37 citation statements)

References 10 publications

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“…According to experimental data (Davidson et al, 1983) and observed anomalies in the depth profile of interstitial water chemistry and 8180 (Hesse and Harrison, 1981;Harrison and Curiale, 1982;Jenden and Gieskes, 1983), gas hydrate is thought to concentrate more 180 than the ambient water (Hesse and Harrison, 1981;Jenden and Gieskes, 1983). The fractionation of oxygen isotope between methane-hydrate and water could be roughly estimated to be + 3 to + 6%o (Harrison and Curiale, 1982;Davidson et al, 1983;Matsumoto, 1989).…”

Section: Anaerobic Vs Aerobic Methane Oxidationmentioning

confidence: 99%

“…The fractionation of oxygen isotope between methane-hydrate and water could be roughly estimated to be + 3 to + 6%o (Harrison and Curiale, 1982;Davidson et al, 1983;Matsumoto, 1989). Accordingly, when a large amount of 18O-enriched methane-hydrate decomposes in near surface sediments, the in terstitial water would increase in 180 by a few per mil due to mixing of hydrate-derived water.…”

Section: Anaerobic Vs Aerobic Methane Oxidationmentioning

confidence: 99%

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Vuggy carbonate crust formed by hydrocarbon seepage on the continental shelf of Baffin Island, northeast Canada.

Matsumoto

1990

Geochem. J.

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Vuggy carbonate crust 10 cm in thickness has been discovered associated with hydrocarbon seepage on the continental shelf of Baffin Island, northeast Canada, at a water depth of about 400 m. The car bonate crust is principally composed of high magnesian calcite (14.1 to 18.1 mol.% MgCO3) with subor dinate amounts of aragonite (---9200 ppm Sr) and calcian dolomite (51.5 to 53.2 mol.% CaCO3). Magne sian calcite occurs as microcrystalline cement, and aragonite forms botryoidal aggregates in cavities and solution pits of the crust. Dolomite occurs as isolated euhedral grains with characteristic corroded sur faces.Calcite and aragonite have the similar isotopic signatures, ranging in 813C between -26.1 and -33 .2%o PDB and in 8180 between 4.4 and 7.8%o PDB. Relative to calcite and aragonite, dolomite is enriched in 13C ( 8.9 to -11.6%o PDB 613C) and depleted in 180 (-1.2 to -1.7%o PDB PO).Combined petrographic and gochemical evidence suggests that dolomite was formed in the sulfate reduction zone prior to the formation of carbonate crust under the strong influence of 18O-depleted freshwater, which presumably was derived from the melting of glacial ice. Then high magnesian calcite precipitated to forma dense carbonate layer in the near surface sediments caused by anaerobic oxida tion of hydrate-derived 13C-depleted methane and increased alkalinity. When the sediments on the crust were winnowed and blown away by an expulsion of methane from the sea bed or a strong bottom cur rent, the crust would be exposed to a zone of aerobic methane oxidation at the sediment/water inter face. This led to dissolution of the upper surface of the crust and subsequent precipitation of botryoidal aragonite within solution vugs and cavities.

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Section: Anaerobic Vs Aerobic Methane Oxidationmentioning

confidence: 99%

Section: Anaerobic Vs Aerobic Methane Oxidationmentioning

confidence: 99%

Vuggy carbonate crust formed by hydrocarbon seepage on the continental shelf of Baffin Island, northeast Canada.

Matsumoto

1990

Geochem. J.

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“…Seismic data near some slump areas show that there are numerous normal faults that sole out at or near the BSR (e.g., Popenoe et al, 1993). If gas hydrate comprises a significant portion of the volume of rise prism sediments above the BSR (Heling, 1970;Harrison and Curiale, 1982), then the physical properties of the sediments would change dramatically when gas hydrate decomposes. Solid gas hydrate decomposes to water plus (overpressured?)…”

Section: Roie In Continental Margin Sediment Instabilitymentioning

confidence: 99%

“…In the process of gas hydrate formation, water and low molecular weight gases (i.e., methane) form a crystalline solid that cements the sediment, leaving the remaining pore fluids enriched in salts (Hesse and Harrison, 1981;Harrison and Curiale, 1982;Ussier and Paull, 1995). At greater depths, gas hydrate breaks down and adds methane and freshwater back into the pore waters, decreasing the salinity and increasing the methane concentration.…”

Section: Modification Of Fluidsmentioning

confidence: 99%

“…This phenomenon has been employed to explain (1) deep-sea sediment cores that contain water with higher δ 18 θ content and lower salinities than seawater as having been generated by the recent breakdown of gas hydrate (Hesse and Harrison, 1981;Harrison and Curiale, 1982;Matsumoto, 1989;Ussier and Paull, 1995) and (2) other pore waters from deeper cores that are isotopically light and saline as resulting from the expulsion of fluids during gas hydrate formation (Kvenvolden and Kastner, 1990).…”

Section: Isotopic Fractionation and Signature Of Pore-water Sourcesmentioning

confidence: 99%

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Leg 164 Introduction

Paull¹,

Matusmoto²,

Wallace³

1996

Proceedings of the Ocean Drilling Program

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Distribution of gas hydrates on continental margins by means of a mathematical envelope: A method applied to the interpretation of 3D Seismic Data

Bale

Alves

Moore

2014

Geochem Geophys Geosyst

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[1] A 3D seismic volume from the Nankai Trough accretionary wedge (SE Japan) is used to evaluate the subsurface distribution of gas hydrates as a function of structural and stratigraphic complexity, variable heat flow patterns and the presence of subsurface fluid conduits. Eleven equations were modified for depth, pressure, and temperature, modeled in 3D, and compared with the distribution of BottomSimulating Reflections (BSRs) offshore Nankai. The results show that the equations produce overlapping-and thus potentially consistent-predictions for the distribution of BSRs, leading us to propose the concept of a ''BSR Stability Envelope'' as a method to quantify the subsurface distribution of gas hydrates on continental margins. In addition, we show that the ratio (R) between shallow and deep BSRs of seven subenvelopes, which are defined by BSR stability equations, indicates local gas hydrate equilibrium conditions. Values of R < 1 relate to cooler regions, whereas when R > 1 the majority of BSRs are located in warmer structural traps. The method in this paper can be used to recognize any divergence between observed and theoretical depths of occurrence of BSRs on 3D or 4D (time lapse) seismic volumes. In the Nankai Trough, our results point out for equilibrium conditions in BSRs located away from the Megasplay Fault Zone and major thrust faults. This latter observation demonstrates the applicability of the method to: (a) the recognition of subsurface fluid conduits and (b) the prediction of maximum and minimum depths of occurrence of gas hydrates on continental margins, under distinct thermal and hydrologic conditions.

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Gas Hydrates in Sediments of Holes 497 and 498A, Deep Sea Drilling Project Leg 67

Cited by 34 publications

References 10 publications

Vuggy carbonate crust formed by hydrocarbon seepage on the continental shelf of Baffin Island, northeast Canada.

Vuggy carbonate crust formed by hydrocarbon seepage on the continental shelf of Baffin Island, northeast Canada.

Leg 164 Introduction

Distribution of gas hydrates on continental margins by means of a mathematical envelope: A method applied to the interpretation of 3D Seismic Data

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