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Title:
Liquid Carbon Dioxide Venting at the Champagne Hydrothermal Site, NW Eifuku Volcano, Mariana Arc
Authors:
Lupton, J.; Lilley, M.; Butterfield, D.; Evans, L.; Embley, R.; Olson, E.; Proskurowski, G.; Resing, J.; Roe, K.; Greene, R.; Lebon, G.
Affiliation:
AA(NOAA Pacific Environmental Laboratory, Hatfield Marine Science Center, Newport, OR 97365 United States ), AB(School of Oceanography, University of Washington, Seattle, WA 98195 United States ;), AC(JISAO, University of Washington and NOAA PMEL, Seattle, WA 98195 United States ;), AD(CIMRS, Oregon State University and NOAA PMEL, Corvallis, OR 97331 United States ;), AE(NOAA Pacific Environmental Laboratory, Hatfield Marine Science Center, Newport, OR 97365 United States ;), AF(School of Oceanography, University of Washington, Seattle, WA 98195 United States ;), AG(School of Oceanography, University of Washington, Seattle, WA 98195 United States ;), AH(JISAO, University of Washington and NOAA PMEL, Seattle, WA 98195 United States ;), AI(JISAO, University of Washington and NOAA PMEL, Seattle, WA 98195 United States ;), AJ(CIMRS, Oregon State University and NOAA PMEL, Corvallis, OR 97331 United States ;), AK(JISAO, University of Washington and NOAA PMEL, Seattle, WA 98195 United States ;)
Publication:
American Geophysical Union, Fall Meeting 2004, abstract id. V43F-08
Publication Date:
12/2004
Origin:
AGU
Keywords:
8424 Hydrothermal systems (8135), 4806 Carbon cycling, 4815 Ecosystems, structure and dynamics, 4820 Gases, 4832 Hydrothermal systems
Bibliographic Code:
2004AGUFM.V43F..08L

Abstract

In March/April 2004, submersible dives with the remotely-operated vehicle ROPOS discovered an unusual CO2-rich hydrothermal system near the summit of NW Eifuku, a submarine volcano located at 21.49° N, 144.04° E in the northern Mariana Arc. Although several sites of hydrothermal discharge were located on NW Eifuku, the most intense venting was found at 1600-m depth at the Champagne site, slightly west of the volcano summit. The Champagne site was found to be discharging two distinct fluids into the ocean: a) several small white chimneys were emitting milky 103° C gas-rich hydrothermal fluid with at least millimolar levels of H2S and b) cold (< 4° C) droplets coated with a milky skin were rising slowly from the sediment. These droplets were later determined to consist mainly of liquid CO2, with H2S as a probable secondary component. The droplets were sticky, and did not tend to coalesce into larger droplets, even though they adhered to the ROV like clumps of grapes. The film coating the droplets was assumed to be CO2 hydrate (or clathrate) which is known to form whenever liquid CO2 contacts water under these P,T conditions. Samples of the 103° C hydrothermal fluids were collected in special gas-tight titanium sampling bottles that were able to withstand the high internal pressures created by the dissolved gases. The Champagne hydrothermal fluids contained a surprising 2.3 moles/kg of CO2, an order of magnitude higher than any CO2 values previously reported for submarine hydrothermal fluids. The overall gas composition was 87% CO2, < 0.1% CH4, < 2 ppm H2, 0.012 mM/kg 4He, with the remaining 13% (322 mM/kg) assumed to be sulfur gases (H2S, SO2, etc.). (Additional analyses planned will confirm the speciation of this sulfur gas component). The helium had R/RA = 7.3, typical of subduction zone systems (R = 3He/4He and RA = Rair). Isotopic analysis of the CO2 yielded δ 13C = -1.75 ‰ , much heavier than the -6.0 ‰ typical for carbon in MOR vent fluids. The C/3He ratio was ~2.2 x 1010, an order of magnitude higher than the average value of 2 x 109 found in MOR vent fluids. The δ 13C and C/3He values suggest a substantial contribution to the carbon from subducted carbonates rather than mantle carbon. The Champagne site is only the second locality where liquid CO2 has been observed venting into the deep sea (the other reported location is in the Okinawa Trough, see Sakai et al., 1990). Because of the presence of liquid CO2 in proximity to hydrothermal organisms, the Champagne site may prove to be a valuable natural laboratory for studying the effects of high CO2 concentrations on marine ecosystems.
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