HR: 16:15h
AN: V34B-02    [Abstracts]
TI: Venting of a Separate CO2-Rich Gas Phase from Submarine Arc Volcanoes
AU: * Lupton, J
EM: john.e.lupton@noaa.gov
AF: NOAA, PMEL, Newport, OR 97365, United States
AU: Lilley, M
AF: School of Oceanography, University of Washington, Seattle, WA 98115, United States
AU: Butterfield, D
AF: JISAO, University of Washington, Seattle, WA 98115, United States
AU: Evans, L
AF: CIMRS, Oregon State University, Newport, OR 97365, United States
AU: Embley, R
AF: NOAA, PMEL, Newport, OR 97365, United States
AU: Massoth, G
AF: Inst. of Geological and Nuclear Sciences, PO Box 31, Lower Hutt, 31-312, New Zealand
AU: Christenson, B
AF: Inst. of Geological and Nuclear Sciences, PO Box 31, Lower Hutt, 31-312, New Zealand
AU: Nakamura, K
AF: National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 7, Tsukuba, 305-8567, Japan
AU: Schmidt, M
AF: Inst. of Geosciences, University of Kiel, Kiel, 24118, Germany
AB: Although CO₂ is typically the most abundant gas dissolved in submarine hydrothermal fluids, it rarely appears as a completely separate phase. Among mid-ocean ridge hydrothermal systems, a significant discharge of pure CO₂ has been found at only one site: the Magic Mountain vent field on the Explorer Ridge, northeast Pacific. In contrast to MOR systems, recent studies of submarine volcanoes on the Mariana and Kermadec Arcs have found several sites that, in addition to discharging hot vent fluid, are also venting a separate CO₂-rich phase either in the form of gas bubbles or liquid CO₂ droplets. One of the most impressive is the Champagne vent site on NW Eifuku in the northern Mariana Arc. This relatively small vent field is discharging cold droplets of liquid CO₂ at an estimated rate of 23 moles CO₂/sec, about 0.1% or the global MOR carbon flux (see Lupton et al., 2006). Three other Mariana Arc submarine volcanoes, NW Rota-1, Nikko, and Daikoku, all have vent fields discharging CO₂ in the form of gas bubbles. At Nikko and Daikoku the CO₂ gas is bubbling up through pools of liquid sulfur. In addition, Pisces dives on the Kermadec Arc in 2005 found venting of CO-rich gas bubbles at Giggenbach volcano and Volcano-1. Based on this limited data set, it appears that a separate CO₂-rich gas phase is a relatively common occurrence on volcanic arcs and almost non-existent on mid-ocean ridges. This difference is probably due to the supply of subducted marine carbonates and organic matter incorporated into the melting process along volcanic arcs, although the shallower depth of submarine arc volcanoes also favors formation of a separate gas phase. At each of the 6 volcanoes considered here, the separate gas phase is also accompanied by venting of hot hydrothermal fluid. Our preliminary analysis indicates that the vent fluid is not in equilibrium with the gas phase, suggesting that the two phases separated at depth in the system. One possibility is that the gas phase results from direct CO₂ degassing from a magma chamber, while the hot vent fluid originates from seawater circulating through the volcanic edifice. These findings indicate that carbon fluxes from submarine arcs may be higher than previously estimated. Detailed experiments to estimate carbon fluxes at submarine arc volcanoes would help to resolve this question.
DE: 1031 Subduction zone processes (3060, 3613, 8170, 8413)
DE: 3017 Hydrothermal systems (0450, 1034, 3616, 4832, 8135, 8424)
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
DE: 8413 Subduction zone processes (1031, 3060, 3613, 8170)
DE: 8430 Volcanic gases
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting