Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean
We report on the geochemistry of hydrocarbons and pore waters down to 62.5 mbsf, collected by drilling with the MARUM‐MeBo70 and by gravity coring at the Lunde pockmark in the Vestnesa Ridge. Our data document the origin and transformations of volatiles feeding gas emissions previously documented in...
Published in: | Journal of Geophysical Research: Solid Earth |
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Format: | Article in Journal/Newspaper |
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Online Access: | https://oceanrep.geomar.de/id/eprint/48110/ https://oceanrep.geomar.de/id/eprint/48110/7/2018JB016679.pdf https://doi.org/10.1029/2018JB016679 |
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ftoceanrep:oai:oceanrep.geomar.de:48110 2023-05-15T14:27:25+02:00 Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean Pape, T. Bünz, S. Hong, W.‐L. Torres, M. E. Riedel, Michael Panieri, G. Lepland, A. Hsu, C.W. Wintersteller, P. Wallmann, Klaus Schmidt, Christopher Yao, H. Bohrmann, Gerhard 2020-01 text https://oceanrep.geomar.de/id/eprint/48110/ https://oceanrep.geomar.de/id/eprint/48110/7/2018JB016679.pdf https://doi.org/10.1029/2018JB016679 en eng AGU Wiley https://oceanrep.geomar.de/id/eprint/48110/7/2018JB016679.pdf Pape, T. , Bünz, S., Hong, W. ‐. , Torres, M. E. , Riedel, M. , Panieri, G. , Lepland, A., Hsu, C. W. , Wintersteller, P., Wallmann, K. , Schmidt, C. , Yao, H. and Bohrmann, G. (2020) Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean. Open Access Journal of Geophysical Research: Solid Earth, 125 (1). Art.Nr. e2018JB016679. DOI 10.1029/2018JB016679 <https://doi.org/10.1029/2018JB016679>. doi:10.1029/2018JB016679 cc_by_nc_nd_4.0 info:eu-repo/semantics/openAccess Article PeerReviewed 2020 ftoceanrep https://doi.org/10.1029/2018JB016679 2023-04-07T15:47:56Z We report on the geochemistry of hydrocarbons and pore waters down to 62.5 mbsf, collected by drilling with the MARUM‐MeBo70 and by gravity coring at the Lunde pockmark in the Vestnesa Ridge. Our data document the origin and transformations of volatiles feeding gas emissions previously documented in this region. Gas hydrates are present where a fracture network beneath the pockmark focusses migration of thermogenic hydrocarbons characterized by their C1/C2+ and stable isotopic compositions (δ2H‐CH4, δ13C‐CH4). Measured geothermal gradients (~80°C km‐1) and known formation temperatures (>70°C) suggest that those hydrocarbons are formed at depths >800 mbsf. A combined analytical/modeling approach, including concentration and isotopic mass balances, reveals that pockmark sediments experience diffuse migration of thermogenic hydrocarbons. However, at sites without channeled flow this appears to be limited to depths > ~50 mbsf. At all sites we document a contribution of microbial methanogenesis to the overall carbon cycle that includes a component of secondary carbonate reduction (CR) – i.e. reduction of dissolved inorganic carbon (DIC) generated by anaerobic oxidation of methane (AOM) in the uppermost methanogenic zone. AOM and CR rates are spatially variable within the pockmark and are highest at high‐flux sites. These reactions are revealed by δ13C‐DIC depletions at the sulfate‐methane interface at all sites. However, δ13C‐CH4 depletions are only observed at the low methane flux sites because changes in the isotopic composition of the overall methane pool are masked at high‐flux sites. 13C‐depletions of TOC suggest that at seeps sites, methane‐derived carbon is incorporated into de novo synthesized biomass. Article in Journal/Newspaper Arctic Arctic Arctic Ocean Lunde OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Arctic Arctic Ocean Lunde ENVELOPE(50.467,50.467,-66.967,-66.967) Journal of Geophysical Research: Solid Earth 125 1 |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
op_collection_id |
ftoceanrep |
language |
English |
description |
We report on the geochemistry of hydrocarbons and pore waters down to 62.5 mbsf, collected by drilling with the MARUM‐MeBo70 and by gravity coring at the Lunde pockmark in the Vestnesa Ridge. Our data document the origin and transformations of volatiles feeding gas emissions previously documented in this region. Gas hydrates are present where a fracture network beneath the pockmark focusses migration of thermogenic hydrocarbons characterized by their C1/C2+ and stable isotopic compositions (δ2H‐CH4, δ13C‐CH4). Measured geothermal gradients (~80°C km‐1) and known formation temperatures (>70°C) suggest that those hydrocarbons are formed at depths >800 mbsf. A combined analytical/modeling approach, including concentration and isotopic mass balances, reveals that pockmark sediments experience diffuse migration of thermogenic hydrocarbons. However, at sites without channeled flow this appears to be limited to depths > ~50 mbsf. At all sites we document a contribution of microbial methanogenesis to the overall carbon cycle that includes a component of secondary carbonate reduction (CR) – i.e. reduction of dissolved inorganic carbon (DIC) generated by anaerobic oxidation of methane (AOM) in the uppermost methanogenic zone. AOM and CR rates are spatially variable within the pockmark and are highest at high‐flux sites. These reactions are revealed by δ13C‐DIC depletions at the sulfate‐methane interface at all sites. However, δ13C‐CH4 depletions are only observed at the low methane flux sites because changes in the isotopic composition of the overall methane pool are masked at high‐flux sites. 13C‐depletions of TOC suggest that at seeps sites, methane‐derived carbon is incorporated into de novo synthesized biomass. |
format |
Article in Journal/Newspaper |
author |
Pape, T. Bünz, S. Hong, W.‐L. Torres, M. E. Riedel, Michael Panieri, G. Lepland, A. Hsu, C.W. Wintersteller, P. Wallmann, Klaus Schmidt, Christopher Yao, H. Bohrmann, Gerhard |
spellingShingle |
Pape, T. Bünz, S. Hong, W.‐L. Torres, M. E. Riedel, Michael Panieri, G. Lepland, A. Hsu, C.W. Wintersteller, P. Wallmann, Klaus Schmidt, Christopher Yao, H. Bohrmann, Gerhard Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean |
author_facet |
Pape, T. Bünz, S. Hong, W.‐L. Torres, M. E. Riedel, Michael Panieri, G. Lepland, A. Hsu, C.W. Wintersteller, P. Wallmann, Klaus Schmidt, Christopher Yao, H. Bohrmann, Gerhard |
author_sort |
Pape, T. |
title |
Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean |
title_short |
Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean |
title_full |
Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean |
title_fullStr |
Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean |
title_full_unstemmed |
Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean |
title_sort |
origin and transformation of light hydrocarbons ascending at an active pockmark on vestnesa ridge, arctic ocean |
publisher |
AGU |
publishDate |
2020 |
url |
https://oceanrep.geomar.de/id/eprint/48110/ https://oceanrep.geomar.de/id/eprint/48110/7/2018JB016679.pdf https://doi.org/10.1029/2018JB016679 |
long_lat |
ENVELOPE(50.467,50.467,-66.967,-66.967) |
geographic |
Arctic Arctic Ocean Lunde |
geographic_facet |
Arctic Arctic Ocean Lunde |
genre |
Arctic Arctic Arctic Ocean Lunde |
genre_facet |
Arctic Arctic Arctic Ocean Lunde |
op_relation |
https://oceanrep.geomar.de/id/eprint/48110/7/2018JB016679.pdf Pape, T. , Bünz, S., Hong, W. ‐. , Torres, M. E. , Riedel, M. , Panieri, G. , Lepland, A., Hsu, C. W. , Wintersteller, P., Wallmann, K. , Schmidt, C. , Yao, H. and Bohrmann, G. (2020) Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean. Open Access Journal of Geophysical Research: Solid Earth, 125 (1). Art.Nr. e2018JB016679. DOI 10.1029/2018JB016679 <https://doi.org/10.1029/2018JB016679>. doi:10.1029/2018JB016679 |
op_rights |
cc_by_nc_nd_4.0 info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1029/2018JB016679 |
container_title |
Journal of Geophysical Research: Solid Earth |
container_volume |
125 |
container_issue |
1 |
_version_ |
1766301134319779840 |