HR: 16:30h
AN: V34B-03    [Abstracts]
TI: Sulfur Lakes and Sulfur-rich Volcanic Hydrothermal Systems on the Mariana Arc
AU: * Butterfield, D A
EM: dab3@u.washington.edu
AF: University of Washington, JISAO Box 357925, Seattle, WA 98105, United States
AU: Resing, J A
EM: joseph.resing@noaa.gov
AF: University of Washington, JISAO Box 357925, Seattle, WA 98105, United States
AU: Chadwick, W W
EM: william.w.chadwick@noaa.gov
AF: Oregon State University, CIMRS 2115 SE OSU Dr, Newport, OR 97365, United States
AU: Embley, R W
EM: robert.w.embley@noaa.gov
AF: NOAA, Pacific Marine Environmental Lab 2115 SE OSU Dr., Newport, OR 97365, United States
AU: Lupton, J E
EM: john.e.lupton@noaa.gov
AF: NOAA, Pacific Marine Environmental Lab 2115 SE OSU Dr., Newport, OR 97365, United States
AU: Nakamura, K
EM: koichi.nakamura@aist.go.jp
AF: National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 7 1-1-1 Higashi, Tsukuba, 305-8567, Japan
AU: Lilley, M D
EM: lilley@u.washington.edu
AF: University of Washington, School of Oceanography Box 357940, Seattle, WA 98105, United States
AU: Huber, J A
EM: jhuber@mbl.edu
AF: Marine Biological Laboratory, Josephine Bay Paul Center 7 MDL Street, Woods Hole, MA 02543, United States
AB: During the Submarine Ring of Fire expeditions in 2004 and 2006, and the Natsushima NT-05-18 expedition in 2005 we investigated and sampled hydrothermal systems on ten submarine volcanoes in the Mariana arc between 13.5 and 23.1 degrees N. The high volatile content of the volcanic arc environment is evident in the CO2 and SO2 dominated fluids sampled and differentiates volcanic arc hydrothermal chemistry from more rock- buffered mid-ocean ridge systems. Sulfur-dominated sites appear to be common on submarine arc volcanoes at water depths shallower than 700 meters. At NW Rota-1 volcano, there is clear evidence of ongoing eruptive activity producing clouds of particulate and molten sulfur as well as mm to m-size glassy volcanic ejecta. The hydrothermal system at NW Rota-1 represents a direct connection to a sub-seafloor magma body, and is one of the only known sites in the world where we can directly sample the solid, liquid and gaseous products of a submarine magmatic hydrothermal system. Fluids (30 to 260 deg C) sampled directly from an eruptive vent have pH as low as 1.0, with a high content of particulate sulfur, excess sulfurous and sulfuric acid, and very low H2S content. Fluids percolating through volcaniclastic sand adjacent to the vent reached 100 deg C and had higher silica, slightly higher pH, and millimolar levels of H2S. The chemistry of both types of fluids is indicative of input of volcanic SO2 and incomplete disproportionation into sulfuric acid and either H2S (in volcaniclastic sands) or elemental sulfur (in the eruptive vent). Highly acidic aqueous fluids attack the basaltic substrate, and carry high levels of iron and aluminum. Daikoku (21.3°N) and Nikko (23.1°N) submarine volcanoes both host active molten sulfur ponds and a wide variety of sulfur flows and deposits. The remarkable molten sulfur pools (~180-200°C) occur without widespread focused venting of hot water and may be maintained by active magmatic degassing of hot CO2/SO2-rich gases that bubble up through the pools. Although diffuse low-temperature hydrothermal vents are widespread on Daikoku and Nikko, they are less vigorous, less acidic and less enriched in sulfur and metals than the vents on NW Rota, possibly reflecting a lower SO2 content in the magmatic gas and a longer pathway between the magmatic heat source and the seafloor.
DE: 1031 Subduction zone processes (3060, 3613, 8170, 8413)
DE: 1036 Magma chamber processes (3618)
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
DE: 8430 Volcanic gases
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting