Fluid evolution and authigenic mineral paragenesis related to salt diapirism – The Mercator mud volcano in the Gulf of Cadiz

Haffert, Laura; Haeckel, Matthias; Liebetrau, Volker; Berndt, Christian; Hensen, Christian; Nuzzo, Marianne; Reitz, Anja; Scholz, Florian; Schönfeld, Joachim; Pérez-García, Carolina; Weise, Stephan M.

doi:10.1016/j.gca.2012.12.016

Cited by 37 publications

(22 citation statements)

References 107 publications

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“…However, elevated temperatures and salinities in the GHSZ that are characteristic of active gas hydrate formation have rarely been reported (Haeckel et al, ; Koch et al, ; Römer et al, ; Torres et al, ). In most instances these anomalies are related to mud volcanoes and seeps connected to salt diapirs, where temperature and salinity signals from sediment depths of several kilometers are advected toward the seafloor (e.g., Aloisi et al, ; Haffert et al, ; Hensen et al, , ; Reitz et al, ; Reitz et al, ). Here we can exclude any influence from such deep processes based on the geochemical data (e.g., Figure ) and seismic information.…”

Section: Discussionmentioning

confidence: 99%

The Mechanism of Methane Gas Migration Through the Gas Hydrate Stability Zone: Insights From Numerical Simulations

et al. 2019

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Free gas migration through the gas hydrate stability zone (GHSZ) and subsequent gas seepage at the seabed are characteristic features in marine gas hydrate provinces worldwide. The biogenic or thermogenic gas is typically transported along faults from deeper sediment strata to the GHSZ. Several mechanisms have been proposed to explain free gas transport through the GHSZ. While inhibition of hydrate formation by elevated salinities and temperatures have been addressed previously in studies simulating unfocused, area-wide upward advection of gas, which is not adequately supported by field observations, the role of focused gas flow through chimney-like structures has been underappreciated in this context. Our simulations suggest that gas migration through the GHSZ is, fundamentally, a result of methane gas supply in excess of its consumption by hydrate formation. The required high gas flux is driven by local overpressure, built up from gas accumulating below the base of the GHSZ that fractures the overburden when exceeding a critical pressure, thereby creating the chimney-like migration pathway. Initially rapid hydrate formation raises the temperature in the chimney structure, thereby facilitating further gas transport through the GHSZ. As a consequence, high hydrate saturations form preferentially close to the seafloor, where temperatures drop to bottom water values, producing a prominent subsurface salinity peak. Over time, hydrates form at a lower rate throughout the chimney structure, while initial temperature elevation and salinity peak dissipate. Thus, our simulations suggest that the near-surface salinity peak and elevated temperatures are a result of transient high-flux gas migration through the GHSZ.

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Section: Discussionmentioning

confidence: 99%

The Mechanism of Methane Gas Migration Through the Gas Hydrate Stability Zone: Insights From Numerical Simulations

et al. 2019

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“…Dissolved

{SO}_{4}^{2 -}

concentrations were determined by ion chromatography onshore. Analytical details are described in Wallmann et al () and Haffert et al ().…”

Section: Methodsmentioning

confidence: 99%

Linked sediment and water‐column methanotrophy at a man‐made gas blowout in the North Sea: Implications for methane budgeting in seasonally stratified shallow seas

Steinle

Schmidt

Bryant

et al. 2016

Limnology & Oceanography

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Large quantities of the greenhouse gas methane (CH4) are stored in the seafloor. The flux of CH4 from the sediments into the water column and finally to the atmosphere is mitigated by a series of microbial methanotrophic filter systems of unknown efficiency at highly active CH4‐release sites in shallow marine settings. Here, we studied CH4‐oxidation and the methanotrophic community at a high‐CH4‐flux site in the northern North Sea (well 22/4b), where CH4 is continuously released since a blowout in 1990. Vigorous bubble emanation from the seafloor and strongly elevated CH4 concentrations in the water column (up to 42 µM) indicated that a substantial fraction of CH4 bypassed the highly active (up to ∼2920 nmol cm−3 d−1) zone of anaerobic CH4‐oxidation in sediments. In the water column, we measured rates of aerobic CH4‐oxidation (up to 498 nM d−1) that were among the highest ever measured in a marine environment and, under stratified conditions, have the potential to remove a significant part of the uprising CH4 prior to evasion to the atmosphere. An unusual dominance of the water‐column methanotrophs by Type II methane‐oxidizing bacteria (MOB) is partially supported by recruitment of sedimentary MOB, which are entrained together with sediment particles in the CH4 bubble plume. Our study thus provides evidence that bubble emission can be an important vector for the transport of sediment‐borne microbial inocula, aiding in the rapid colonization of the water column by methanotrophic communities and promoting their persistence close to highly active CH4 point sources.

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“…Ion chromatography (Methrom 761) was used to determine sulfate (SO 2− 4 ) in the onshore laboratory with a detection limit of < 100 µM and precision of 200 µM. Major cations were determined by ICP-AES with a detection limit and precision as given by Haffert et al (2013).…”

Section: Ammonium (Nh +mentioning

confidence: 99%

Organic carbon production, mineralization and preservation on the Peruvian margin

Dale¹,

Sommer²,

Lomnitz³

et al. 2014

Preprint

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Abstract. Carbon cycling in Peruvian margin sediments (11° S and 12° S) was examined at 16 stations from 74 m on the inner shelf down to 1024 m water depth by means of in situ flux measurements, sedimentary geochemistry and modeling. Bottom water oxygen was below detection limit down to ca. 400 m and increased to 53 μM at the deepest station. Sediment accumulation rates and benthic dissolved inorganic carbon fluxes decreased rapidly with water depth. Particulate organic carbon (POC) content was lowest on the inner shelf and at the deep oxygenated stations (< 5%) and highest between 200 and 400 m in the oxygen minimum zone (OMZ, 15–20%). The organic carbon burial efficiency (CBE) was unexpectedly low on the inner shelf (< 20%) when compared to a global database, for reasons which may be linked to the frequent ventilation of the shelf by oceanographic anomalies. CBE at the deeper oxygenated sites was much higher than expected (max. 81%). Elsewhere, CBEs were mostly above the range expected for sediments underlying normal oxic bottom waters, with an average of 51 and 58% for the 11° S and 12° S transects, respectively. Organic carbon rain rates calculated from the benthic fluxes alluded to a very efficient mineralization of organic matter in the water column, with a Martin curve exponent typical of normal oxic waters (0.88 ± 0.09). Yet, mean POC burial rates were 2–5 times higher than the global average for continental margins. The observations at the Peruvian margin suggest that a lack of oxygen does not affect the degradation of organic matter in the water column but promotes the preservation of organic matter in marine sediments.

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Fluid evolution and authigenic mineral paragenesis related to salt diapirism – The Mercator mud volcano in the Gulf of Cadiz

Cited by 37 publications

References 107 publications

The Mechanism of Methane Gas Migration Through the Gas Hydrate Stability Zone: Insights From Numerical Simulations

The Mechanism of Methane Gas Migration Through the Gas Hydrate Stability Zone: Insights From Numerical Simulations

Linked sediment and water‐column methanotrophy at a man‐made gas blowout in the North Sea: Implications for methane budgeting in seasonally stratified shallow seas

Organic carbon production, mineralization and preservation on the Peruvian margin

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