scholarly journals Climatically driven instability of marine methane hydrate along a canyon-incised continental margin

Geology ◽  
2021 ◽  
Author(s):  
Richard J. Davies ◽  
Miguel Ángel Morales Maqueda ◽  
Ang Li ◽  
Mark Ireland
Keyword(s):  
Methane Hydrate ◽  
Ocean Warming ◽  
Stability Field ◽  
Continental Margins ◽  
Stability Zone ◽  
Show Evidence ◽  
Past Climate Change ◽  
The Stability ◽  
The Impact ◽  
Hydrate Stability

Establishing how past climate change affected the stability of marine methane hydrate is important for our understanding of the impact of a future warmer world. As oceans shallow toward continental margins, the base of the hydrate stability zone also shallows, and this delineates the feather edge of marine methane hydrate. It is in these rarely documented settings that the base of the hydrate stability zone intersects the seabed and hydrate can crop out where it is close to being unstable and most susceptible to dissociation due to ocean warming. We show evidence for a seismically defined outcrop zone intersecting canyons on a canyon-incised margin offshore of Mauritania. We propose that climatic, and hence ocean, warming since the Last Glacial Maximum as well as lateral canyon migration, cutting, and filling caused multiple shifts of the hydrate stability field, and therefore hydrate instability and likely methane release into the ocean. This is particularly significant because the outcrop zone is longer on canyon-incised margins than on less bathymetrically complex submarine slopes. We propose considerably more hydrate will dissociate in these settings during future ocean warming, releasing methane into the world’s oceans.

scholarly journals INFLUENCE OF SALT DIFFUSION ON THE STABILITY OF METHANE GAS HYDRATE IN THE ARCTIC SHELF

2020 ◽  
Vol 4 (1) ◽  
pp. 91-97
Author(s):  
Valentina V. Malakhova
Keyword(s):  
Bottom Sediments ◽  
Methane Hydrate ◽  
Arctic Shelf ◽  
The Arctic ◽  
Stability Zone ◽  
Hydrate Dissociation ◽  
Dissociation Temperature ◽  
The Stability ◽  
Salt Diffusion ◽  
Hydrate Stability

Suitable conditions for the formation of methane hydrates exist in the bottom sediments of shallow Arctic shelves in the presence of permafrost. Salt diffusion into hydrated bottom sediments can help accelerate hydrate degradation. An analysis of the influence of salinity of the bottom sediments of the Arctic shelf on the thickness of the methane hydrate stability zone was based on mathematical modeling. Estimates of the thickness of the stability zone were obtained in experiments with various correlations which relate the hydrate dissociation temperature in the presence of aqueous solutions containing salts.

scholarly journals Gas Seeps at the Edge of the Gas Hydrate Stability Zone on Brazil’s Continental Margin

Geosciences ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 193 ◽  
Author(s):  
Marcelo Ketzer ◽  
Daniel Praeg ◽  
Maria A.G. Pivel ◽  
Adolpho H. Augustin ◽  
Luiz F. Rodrigues ◽  
...  
Keyword(s):  
Gravitational Collapse ◽  
Continental Margin ◽  
Gas Hydrate ◽  
Deep Sea ◽  
Rio Grande ◽  
Cold Seep ◽  
Stability Zone ◽  
The Stability ◽  
Sea Fan ◽  
Hydrate Stability

Gas hydrate provinces occur in two sedimentary basins along Brazil’s continental margin: (1) The Rio Grande Cone in the southeast, and (2) the Amazon deep-sea fan in the equatorial region. The occurrence of gas hydrates in these depocenters was first detected geophysically and has recently been proven by seafloor sampling of gas vents, detected as water column acoustic anomalies rising from seafloor depressions (pockmarks) and/or mounds, many associated with seafloor faults formed by the gravitational collapse of both depocenters. The gas vents include typical features of cold seep systems, including shallow sulphate reduction depths (<4 m), authigenic carbonate pavements, and chemosynthetic ecosystems. In both areas, gas sampled in hydrate and in sediments is dominantly formed by biogenic methane. Calculation of the methane hydrate stability zone for water temperatures in the two areas shows that gas vents occur along its feather edge (water depths between 510 and 760 m in the Rio Grande Cone and between 500 and 670 m in the Amazon deep-sea fan), but also in deeper waters within the stability zone. Gas venting along the feather edge of the stability zone could reflect gas hydrate dissociation and release to the oceans, as inferred on other continental margins, or upward fluid flow through the stability zone facilitated by tectonic structures recording the gravitational collapse of both depocenters. The potential quantity of venting gas on the Brazilian margin under different scenarios of natural or anthropogenic change requires further investigation. The studied areas provide natural laboratories where these critical processes can be analyzed and quantified.

The Double (or Multiple) BSRs Observations and their Tentative Interpretations

2013 ◽  
Vol 734-737 ◽  
pp. 467-475
Author(s):  
Yi Luo ◽  
Xin Su
Keyword(s):  
Climate Change ◽  
Marine Environment ◽  
Gas Hydrate ◽  
Seismic Reflection ◽  
Continental Margins ◽  
Tectonic Movement ◽  
Stability Zone ◽  
Bottom Simulating Reflector ◽  
Seismic Reflection Profiles ◽  
Hydrate Stability

Gas hydrate is a solid ice-like compound and is stable at low temperature and high pressure conditions found beneath permafrost and in marine sediments on continental margins offshore. In the marine environment, the bottom-simulating reflector (BSR) in seismic reflection profiles is interpreted to indicate the base of the gas hydrate stability zone (GHSZ).In many locations two or more sub-parallel BSRs have been reported. We not only compared the BSRs characteristics from reported areas but also discussed the mechanism of GHSZ shifts by climate change, sedimentation process and tectonic movement. We also considered the mix gases composition hydrate stability in certain marine environment and gave a simple model for the BSR differences on water depth.

Formation of Methane Hydrates from Super-compressed Water and Methane Mixtures

2010 ◽  
Vol 1262 ◽  
Author(s):  
Jing-Yin Chen ◽  
Choong-Shik Yoo
Keyword(s):  
Methane Hydrate ◽  
High Speed ◽  
Energy Resource ◽  
Hydrate Formation ◽  
Methane Hydrates ◽  
Stability Field ◽  
Compression Rate ◽  
Time Resolved ◽  
Optical Images ◽  
The Stability

AbstractUnderstanding the high-pressure kinetics associated with the formation of methane hydrates is critical to the practical use of the most abundant energy resource on earth. In this study, we have studied, for the first time, the compression rate dependence on the formation of methane hydrates under pressures, using dynamic-Diamond Anvil Cell (d-DAC) coupled with a high-speed microphotography and a confocal micro-Raman spectroscopy. The time-resolved optical images and Raman spectra indicate that the pressure-induced formation of methane hydrate depends on the compression rate and the peak pressure. At the compression rate of around 5 to 10 GPa/s, methane hydrate phase II (MH-II) forms from super-compressed water within the stability field of ice VI between 0.9 GPa and 2.0 GPa. This is due to a relatively slow rate of the hydrate formation below 0.9 GPa and a relatively fast rate of the water solidification above 2.0 GPa. The fact that methane hydrate forms from super-compressed water underscores a diffusion-controlled growth, which accelerates with pressure because of the enhanced miscibility between methane and super-compressed water.

Interface instability of methane hydrate stability zone in permafrost deposits

2012 ◽  
Vol 27 (5) ◽  
pp. 637-650 ◽  
Author(s):  
Ekaterina Kolchanova ◽  
Tatyana Lyubimova ◽  
Dmitry Lyubimov ◽  
Oleg Zikanov
Keyword(s):  
Methane Hydrate ◽  
Stability Zone ◽  
Interface Instability ◽  
Hydrate Stability

scholarly journals Evidences for Paleo-Gas Hydrate Occurrence: What We Can Infer for the Miocene of the Northern Apennines (Italy)

Geosciences ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 134 ◽  
Author(s):  
Claudio Argentino ◽  
Stefano Conti ◽  
Chiara Fioroni ◽  
Daniela Fontana
Keyword(s):  
Gas Hydrates ◽  
Gas Hydrate ◽  
Northern Apennines ◽  
Stability Field ◽  
Continental Margins ◽  
Shallow Gas ◽  
Hydrate Decomposition ◽  
Oxygen Isotopic ◽  
The Stability ◽  
Seep Carbonate

The occurrence of seep-carbonates associated with shallow gas hydrates is increasingly documented in modern continental margins but in fossil sediments the recognition of gas hydrates is still challenging for the lack of unequivocal proxies. Here, we combined multiple field and geochemical indicators for paleo-gas hydrate occurrence based on present-day analogues to investigate fossil seeps located in the northern Apennines. We recognized clathrite-like structures such as thin-layered, spongy and vuggy textures and microbreccias. Non-gravitational cementation fabrics and pinch-out terminations in cavities within the seep-carbonate deposits are ascribed to irregularly oriented dissociation of gas hydrates. Additional evidences for paleo-gas hydrates are provided by the large dimensions of seep-carbonate masses and by the association with sedimentary instability in the host sediments. We report heavy oxygen isotopic values in the examined seep-carbonates up to +6‰ that are indicative of a contribution of isotopically heavier fluids released by gas hydrate decomposition. The calculation of the stability field of methane hydrates for the northern Apennine wedge-foredeep system during the Miocene indicated the potential occurrence of shallow gas hydrates in the upper few tens of meters of sedimentary column.

scholarly journals First synthesis of a unique icosahedral phase from the Khatyrka meteorite by shock-recovery experiment

IUCrJ ◽  
2020 ◽  
Vol 7 (3) ◽  
pp. 434-444 ◽  
Author(s):  
Jinping Hu ◽  
Paul D. Asimow ◽  
Chi Ma ◽  
Luca Bindi
Keyword(s):  
Phase Ii ◽  
Full Range ◽  
Icosahedral Phase ◽  
304 Stainless Steel ◽  
Target Chamber ◽  
Stability Field ◽  
Novel Strategy ◽  
The Stability ◽  
The Impact ◽  
Shock Recovery Experiments

Icosahedral quasicrystals (i-phases) in the Al–Cu–Fe system are of great interest because of their perfect quasicrystalline structure and natural occurrences in the Khatyrka meteorite. The natural quasicrystal of composition Al62Cu31Fe7, referred to as i-phase II, is unique because it deviates significantly from the stability field of i-phase and has not been synthesized in a laboratory setting to date. Synthetic i-phases formed in shock-recovery experiments present a novel strategy for exploring the stability of new quasicrystal compositions and prove the impact origin of natural quasicrystals. In this study, an Al–Cu–W graded density impactor (GDI, originally manufactured as a ramp-generating impactor but here used as a target) disk was shocked to sample a full range of Al/Cu starting ratios in an Fe-bearing 304 stainless-steel target chamber. In a strongly deformed region of the recovered sample, reactions between the GDI and the steel produced an assemblage of co-existing Al61.5Cu30.3Fe6.8Cr1.4 i-phase II + stolperite (β, AlCu) + khatyrkite (θ, Al2Cu), an exact match to the natural i-phase II assemblage in the meteorite. In a second experiment, the continuous interface between the GDI and steel formed another more Fe-rich quinary i-phase (Al68.6Fe14.5Cu11.2Cr4Ni1.8), together with stolperite and hollisterite (λ, Al13Fe4), which is the expected assemblage at phase equilibrium. This study is the first laboratory reproduction of i-phase II with its natural assemblage. It suggests that the field of thermodynamically stable icosahedrite (Al63Cu24Fe13) could separate into two disconnected fields under shock pressure above 20 GPa, leading to the co-existence of Fe-rich and Fe-poor i-phases like the case in Khatyrka. In light of this, shock-recovery experiments do indeed offer an efficient method of constraining the impact conditions recorded by quasicrystal-bearing meteorite, and exploring formation conditions and mechanisms leading to quasicrystals.

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