Conference proceeding
Geological characteristics of the Shinkai Seep Field, a serpentinite-hosted ecosystem in the southern Mariana Forearc
American Geophysical Union Fall Meeting, Vol.2012
American Geophysical Union 2012 fall meeting
12/2012
Abstract
Most hydrothermal vents along mid-ocean spreading ridges are high-temperature, sulfide-rich, and low pH (acidic environments). For this reason, the discovery of the Lost City hydrothermal field on the Mid-Atlantic Ridge has stimulated interest in the role of serpentinization of peridotite in generating H2- and CH4-rich fluids and associated carbonate chimneys, as well as in the biological communities adapted to highly reduced, alkaline environments. A new serpentinite-hosted ecosystem, the Shinkai Seep Field (SSF), was discovered by a Shinkai 6500 dive in the inner trench slope of the southern Mariana Trench, near the Challenger Deep, during YK10-12 cruise of R/V Yokosuka in September 2010. Abundant chemosynthetic biological communities, principally consisting of vesicomyid clams are associated with serpentinized peridotite in the SSF. Serpentinization beneath several hydrothermal sites on the Mid-Atlantic Ridge is controlled by interacting seawater and peridotite, variably influenced by magmatic heat. In contrast, the SSF is located in a deep inner trench slope where magmatic heat contribution is unlikely. Instead, serpentinization reactions feeding the SSF may be controlled by persistent fluid flow from the subducting slab. Slab-derived fluid flow is probably controlled by flow through fractures because no serpentinite mud volcano can be discerned along the southern Mariana forearc. Deep-towed IMI-30 sonar backscatter imaging during TN273 cruise of R/V Thomas G. Thompson in January 2012 indicates that the SSF is associated with a small, low backscatter feature that may be a small mound. There are 20 or more of these features in the imaged area, the size of which is approximately 200 m width and approximately 200 m to approximately 700 m long. Since the southern Mariana forearc is heavily faulted, with a deep geology that is dominated by peridotite, more SSF-type seeps are likely to exist along the forearc above the Challenger Deep. The discovery of the SSF suggests that serpentinite-hosted vents may be more widespread on the ocean floor than presently known. The discovery further indicates that such serpentinite-hosted low-temperature fluid vents can sustain high-biomass communities and has implications for the chemical budget of the oceans and the distribution of abyssal chemosynthetic life. Since we know nothing about the chemistry and microbiology of the SSF, we hope to return for further studies with Shinkai 6500 in 2013.
Details
- Title: Subtitle
- Geological characteristics of the Shinkai Seep Field, a serpentinite-hosted ecosystem in the southern Mariana Forearc
- Creators
- Y Ohara - Japan Coast Guard, Hydrography and Oceanography Department Tokyo JPN JapanR. J SternF MartinezK MichibayashiM. K ReaganK FujikuraH WatanabeT IshiiK. A Kelley
- Resource Type
- Conference proceeding
- Publication Details
- American Geophysical Union Fall Meeting, Vol.2012
- Conference
- American Geophysical Union 2012 fall meeting
- Publisher
- American Geophysical Union
- Alternative title
- AGU 2012 fall meeting
- Language
- English
- Date published
- 12/2012
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229173802771
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