Physical properties, gas compositon, and δ¹³C DIC measured on sediment cores from an active pockmark on Vestnesa Ridge, Arctic Ocean ...

• Main Authors: Pape, Thomas, Malnati, Janice, Bohrmann, Gerhard
• Format: Article in Journal/Newspaper
• Language: English
• Published: PANGAEA 2019
• Subjects: Center for Marine Environmental Sciences MARUM; Arctic; Arctic Ocean; Lunde
• Online Access: https://dx.doi.org/10.1594/pangaea.905864; https://doi.pangaea.de/10.1594/PANGAEA.905864

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 ...