Vodyanitskii mud volcano, Sorokin trough, Black Sea: Geological characterization and quantification of gas bubble streams

Heiko Sahling, Gerhard Bohrmann, Yuriy G. Artemov, André Bahr, Markus Brüning, Stephan A. Klapp, Ingo Klaucke, Elena Kozlova, Aneta Nikolovska, Thomas Pape, Anja Reitz, Klaus Wallmann

    Research output: Contribution to journalArticlepeer-review

    77 Citations (Scopus)

    Abstract

    Vodyanitskii mud volcano is located at a depth of about 2070 m in the Sorokin Trough, Black sea. It is a 500-m wide and 20-m high cone surrounded by a depression, which is typical of many mud volcanoes in the Black Sea. 75 kHz sidescan sonar show different generations of mud flows that include mud breccia, authigenic carbonates, and gas hydrates that were sampled by gravity coring. The fluids that flow through or erupt with the mud are enriched in chloride (up to ∼650 mmol L-1 at ∼150-cm sediment depth) suggesting a deep source, which is similar to the fluids of the close-by Dvurechenskii mud volcano. Direct observation with the remotely operated vehicle Quest revealed gas bubbles emanating at two distinct sites at the crest of the mud volcano, which confirms earlier observations of bubble-induced hydroacoustic anomalies in echosounder records. The sediments at the main bubble emission site show a thermal anomaly with temperatures at ∼60 cm sediment depth that were 0.9 °C warmer than the bottom water. Chemical and isotopic analyses of the emanated gas revealed that it consisted primarily of methane (99.8%) and was of microbial origin (δD-CH4 = -170.8‰ (SMOW), δ13C-CH4 = -61.0‰ (V-PDB), δ13C-C2H6 = -44.0‰ (V-PDB)). The gas flux was estimated using the video observations of the ROV. Assuming that the flux is constant with time, about 0.9 ± 0.5 × 106 mol of methane is released every year. This value is of the same order-of-magnitude as reported fluxes of dissolved methane released with pore water at other mud volcanoes. This suggests that bubble emanation is a significant pathway transporting methane from the sediments into the water column.

    Original languageEnglish
    Pages (from-to)1799-1811
    Number of pages13
    JournalMarine and Petroleum Geology
    Volume26
    Issue number9
    DOIs
    Publication statusPublished - Nov 2009

    Keywords

    • Bubble emanation
    • Fluid seepage
    • Methane flux
    • Mud volcanism

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