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Geophysical and geochemical signatures associated with gas hydrate-related venting in the northern Cascadia margin

2005; Geological Society of America; Volume: 118; Issue: 1-2 Linguagem: Inglês

10.1130/b25720.1

1943-2674

Michael Riedel, Ivana Novosel, G. D. Spence, R. D. Hyndman, Ross Chapman, R. C. Solem, T. Lewis,

Atmospheric and Environmental Gas Dynamics

Research Article| January 01, 2006 Geophysical and geochemical signatures associated with gas hydrate–related venting in the northern Cascadia margin Michael Riedel; Michael Riedel 1Natural Resources Canada, Geological Survey of Canada–Pacific, 9860 West Saanich Road, Sidney, British Columbia V8L 4B2, Canada Search for other works by this author on: GSW Google Scholar Ivana Novosel; Ivana Novosel 2School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055, Victoria, British Columbia V8W 3P6, Canada Search for other works by this author on: GSW Google Scholar George D. Spence; George D. Spence 2School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055, Victoria, British Columbia V8W 3P6, Canada Search for other works by this author on: GSW Google Scholar Roy D. Hyndman; Roy D. Hyndman 3Natural Resources Canada, Geological Survey of Canada–Pacific, 9860 West Saanich Road, Sidney, British Columbia V8L 4B2, Canada Search for other works by this author on: GSW Google Scholar Ross N. Chapman; Ross N. Chapman 4School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055, Victoria, British Columbia V8W 3P6, Canada Search for other works by this author on: GSW Google Scholar Richard C. Solem; Richard C. Solem 5Scripps Institution of Oceanography, University of California–San Diego, La Jolla, California 92093-0212, USA Search for other works by this author on: GSW Google Scholar Trevor Lewis Trevor Lewis 6Sidney Geophysical Consultants Ltd., 1107 Maple Road, Sidney, British Columbia V8L 5P5, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Michael Riedel 1Natural Resources Canada, Geological Survey of Canada–Pacific, 9860 West Saanich Road, Sidney, British Columbia V8L 4B2, Canada Ivana Novosel 2School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055, Victoria, British Columbia V8W 3P6, Canada George D. Spence 2School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055, Victoria, British Columbia V8W 3P6, Canada Roy D. Hyndman 3Natural Resources Canada, Geological Survey of Canada–Pacific, 9860 West Saanich Road, Sidney, British Columbia V8L 4B2, Canada Ross N. Chapman 4School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055, Victoria, British Columbia V8W 3P6, Canada Richard C. Solem 5Scripps Institution of Oceanography, University of California–San Diego, La Jolla, California 92093-0212, USA Trevor Lewis 6Sidney Geophysical Consultants Ltd., 1107 Maple Road, Sidney, British Columbia V8L 5P5, Canada Publisher: Geological Society of America Received: 10 Sep 2004 Revision Received: 05 May 2005 Accepted: 11 Jun 2005 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2006) 118 (1-2): 23–38. https://doi.org/10.1130/B25720.1 Article history Received: 10 Sep 2004 Revision Received: 05 May 2005 Accepted: 11 Jun 2005 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Michael Riedel, Ivana Novosel, George D. Spence, Roy D. Hyndman, Ross N. Chapman, Richard C. Solem, Trevor Lewis; Geophysical and geochemical signatures associated with gas hydrate–related venting in the northern Cascadia margin. GSA Bulletin 2006;; 118 (1-2): 23–38. doi: https://doi.org/10.1130/B25720.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract This paper presents a comprehensive, multidisciplinary study of cold vents associated with near-seafloor gas hydrate. Several cold vents characterized by seismic blank zones have been identified on the northern Cascadia margin near Ocean Drilling Program (ODP) Site 889/890. The most prominent vent site (Bullseye vent) has been the subject of intense geophysical and geochemical studies, including two- and three-dimensional (2D/3D) seismic imaging, heat flow measurements, piston coring with measurements of sediment physical properties and pore-fluid geochemistry, seafloor video observation, and sampling with the unmanned submersible ROPOS. The main seismically derived constraining observations are: (1) blanking increases with seismic frequency, (2) at low frequencies, layers can be traced through the zones, (3) blank zones widen with depth, (4) blank zones are underlain by a bottom simulating reflector (BSR), and (5) no velocity anomalies were detected across the vents. Constraints from piston core and thermal probe analyses are: (1) massive hydrate was recovered just below the seafloor at Bullseye vent, and (2) chemical alteration of sediments was observed by reduced magnetic susceptibility, increased thermal conductivity, and an elevated sulfate/methane interface. Additional constraints are: (1) no thermal anomaly was observed, (2) widespread carbonates and active chemosynthetic communities were found, and (3) elevated levels of methane were detected in the water column above Bullseye vent.We present a model for the seismic blanking at Bullseye vent that honors the constraints from all observations. The cold vents represent channels or networks of filamentous fractures containing hydrate and/or free gas. Free gas can be present within the hydrate stability field only in fractures, which may be coated with hydrate that prevents the inflow of water. The overall concentration of hydrate or gas within the vent must be small, because there was no observable velocity anomaly. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.