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Title: Towards quantifying the reaction network around the sulfate–methane-transition-zone in the Ulleung Basin, East Sea, with a kinetic modeling approach

We present a kinetic model based upon pore water data collected from eight sites drilled during the second Ulleung Basin gas hydrate drilling expedition (UBGH2) in 2010. Three sites were drilled at locations where acoustic chimneys were identified in seismic data, and the rest were drilled on non-chimney (i.e. background) environments. Our model, coupled a comprehensive compositional and isotopic data set, is used to illustrate the different biogeochemical processes at play in those two environments, in terms of reactions around the sulfate-methane-transition-zone (SMTZ). Organic matter decomposition is an important process for production of methane, dissolved inorganic carbon (DIC) and consumption of sulfate in the non-chimney sites, whereas anaerobic oxidation of methane (AOM) dominates both carbon and sulfur cycles in the chimney environment. Different sources of methane mediate AOM in the two settings. Internally produced methane through CO₂ reduction (CR) and methanogenesis fuels AOM in the non-chimney sites, whereas AOM is sustained by methane from external sources in the chimney sites. We also simulate the system evolution from non-chimney to chimney conditions by increasing the bottom methane supply to a non-chimney setting. We show that the higher CH₄ flux leads to a higher microbial activity of AOM, and more organic mattermore » decomposition through methanogenesis. A higher methanogenesis rate and a smaller CR contribution relative to AOM in the chimney sites is responsible for the isotopically light DIC and heavy methane in this environment, relative to the non-chimney sites.« less
 [1] ;  [1] ;  [2] ;  [2] ;  [2]
  1. Oregon State Univ., Corvallis, OR (United States). College of Earth, Ocean, and Atmospheric Sciences
  2. Korea Inst. of Geosciences and Mineral Resources Daejeon (Korea, Republic of). Petroleum and Marine Research Div.
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 140; Journal Issue: C; Journal ID: ISSN 0016-7037
The Geochemical Society; The Meteoritical Society
Research Org:
Oregon State Univ., Corvallis, OR (United States)
Sponsoring Org:
Country of Publication:
United States