Carbon release from submarine seeps at the Costa Rica fore arc; implications for the volatile cycle at the Central America convergent margin

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doi: 10.1029/2009GC002810
Author(s): Füri, Evelyn; Hilton, David R.; Tryon, Michael D.; Brown, Kevin M.; McMurtry, Gary M.; Brückmann, Warner; Wheat, C. Geoffrey
Author Affiliation(s): Primary:
Scripps Institution of Oceanography, Geosciences Research Division, San Diego, CA, United States
Other:
University of Hawaii at Manoa, United States
University of Kiel, Germany
University of Alaska at Fairbanks, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 11(4). Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 94 refs.; illus., incl. 3 tables, sketch map
Summary: We report total dissolved inorganic carbon (DIC) abundances and isotope ratios, as well as helium isotope ratios (3He/4He), of cold seep fluids sampled at the Costa Rica fore arc in order to evaluate the extent of carbon loss from the submarine segment of the Central America convergent margin. Seep fluids were collected over a 12 month period at Mound 11, Mound 12, and Jaco Scar using copper tubing attached to submarine flux meters operating in continuous pumping mode. The fluids show minimum 3He/4He ratios of 1.3 RA (where RA is air 3He/4He), consistent with a small but discernable contribution of mantle-derived helium. At Mound 11, δ13CΣCO2 values between -23.9 ppm and -11.6 ppm indicate that DIC is predominantly derived from deep methanogenesis and is carried to the surface by fluids derived from sediments of the subducting slab. In contrast, at Mound 12, most of the ascending dissolved methane is oxidized due to lower flow rates, giving extremely low δ13CΣCO2 values ranging from -68.2 ppm to -60.3 ppm. We estimate that the carbon flux (CO2 plus methane) through submarine fluid venting at the outer fore arc is 8.0×105 g C km-1 yr-1, which is virtually negligible compared to the total sedimentary carbon input to the margin and the output at the volcanic front. Unless there is a significant but hitherto unidentified carbon flux at the inner fore arc, the implication is that most of the carbon being subducted in Costa Rica must be transferred to the (deeper) mantle, i.e., beyond the depth of arc magma generation.
Year of Publication: 2010
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Alvin; Basins; C-13/C-12; Carbon; Carbon cycle; Caribbean Plate; Caribbean region; Central America; Cocos Plate; Cold seeps; Continental margin; Costa Rica; East Pacific; Fluid phase; Fore-arc basins; Geochemical cycle; He-4/He-3; Helium; Isotope ratios; Isotopes; Leg 170; Leg 205; Magmas; Marine environment; Ne-20; Neon; Nicoya Peninsula; Noble gases; North Pacific; Northeast Pacific; Ocean Drilling Program; Ocean floors; Pacific Ocean; Plate convergence; Plate tectonics; Sampling; Sea water; Solutes; Stable isotopes; Subduction zones; Submarine environment; Submersibles; Volatiles
Coordinates: N090000 N103000 W0840000 W0860000
Record ID: 2011005723
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