Noble gas anomalies related to high-intensity methane gas seeps in the Black Sea

Holzner, C.P.; McGinnis, Daniel Frank; Schubert, C.J.; Kipfer, R.; Imboden, D.M.

doi:10.1016/j.epsl.2007.10.029

Scientific article

English

Noble gas anomalies related to high-intensity methane gas seeps in the Black Sea

Contributors

Holzner, C.P.; McGinnis, Daniel Frank

; Schubert, C.J.; Kipfer, R.; Imboden, D.M.

Published in

Earth and planetary science letters, vol. 265, no. 3-4, p. 396-409

Publication date

2008

Abstract

Dissolved noble gases and tritium were analyzed at a series of high-intensity methane gas seeps in the Black Sea to study the transport and gas exchange induced by bubble-streams in the water column. These processes affect marine methane emissions to the atmosphere and are therefore relevant to climate warming. The seep areas investigated are located in the Dnepr paleo-delta, west of Crimea, and in the Sorokin Trough mud volcano area, south-east of Crimea. Noble gas concentration profiles at active seep sites revealed prominent anomalies compared to reference profiles that are unaffected by outgassing. Supersaturations of the light noble gases helium and neon observed relatively close to the sea floor are interpreted as effects of gas exchange between the water and the rising bubbles. Depletions of the heavy noble gases argon, krypton and xenon that were detected above an active, bubble-releasing mud volcano appear to be related to the injection of fluids depleted in noble gases that undergo vertical transport in the water column due to small density differences. In both cases, the noble gas anomalies clearly document seep-specific processes which are difficult to detect by other methods. Helium is generally enriched in the deep water of the Black Sea due to terrigenic input. Although exceptionally high helium concentrations observed in one seep area indicate a locally elevated helium flux, most of the seeps studied seem to be negligible sources of terrigenic helium. Noble gas analyses of sediment pore waters from the vicinity of a mud volcano showed large vertical gradients in helium concentrations. The helium isotope signature of the pore waters points to a crustal origin for helium, whereas the deep water of the Black Sea also contains a small mantle-type component.

UNIGE affiliation entities

Not a UNIGE publication

Citation (ISO format)

HOLZNER, C.P. et al. Noble gas anomalies related to high-intensity methane gas seeps in the Black Sea. In: Earth and planetary science letters, 2008, vol. 265, n° 3-4, p. 396–409. doi: 10.1016/j.epsl.2007.10.029

Article (Published version)

Identifiers

PID : unige:40696
DOI : 10.1016/j.epsl.2007.10.029

Additional URL for this publication

http://linkinghub.elsevier.com/retrieve/pii/S0012821X07006747

Journal ISSN

0012-821X

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30/10/2024 20:14:29

Noble gas anomalies related to high-intensity methane gas seeps in the Black Sea

Contributors

Published in

Publication date

Abstract

UNIGE affiliation entities

Citation (ISO format)

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Additional URL for this publication

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Creation

First validation

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Status update

Last indexation