HR: 0800h
AN: T31A-0492    [Abstracts]
TI: The Relationship of Changes in the 9 50'N EPR Hydrothermal System to Observed Seismicity: 2002-2004
AU: * Von Damm, K L
EM: kvd@eos.sr.unh.edu
AF: Complex Systems Research Center, EOS, University of New Hampshire, 366 Morse Hall, Durham, NH 03824-3525 United States
AU: Parker, C M
EM: cheryl.parker@unh.edu
AF: Complex Systems Research Center, EOS, University of New Hampshire, 366 Morse Hall, Durham, NH 03824-3525 United States
AU: Beers, K A
EM: kbeers@cisunix.unh.edu
AF: Complex Systems Research Center, EOS, University of New Hampshire, 366 Morse Hall, Durham, NH 03824-3525 United States
AB: There have been profound changes in the chemistry and temperature of hydrothermal vent fluids sampled in the 9°50'N area of the East Pacific Rise, one of the RIDGE2000 Integrated Study Sites. While hydrothermal fluids have been frequently sampled from this site since 1991, the deployment in September 2003 of an array to detect seismicity provides the opportunity to more quantitatively tie temperature, chemistry, and seismicity together than the previous, and very brief, seismometer deployments here in 1991 and 1995. Seismic swarms were noted in the 9°50'N area beginning on 11/19/2003 [Tolstoy et al. this session], five days after we sampled these fluids. Fluid samples were again collected in March 2004. We also deployed recording temperature probes in all of the high temperature vents at this site in early November 2003. The only vent fluids to show large chemical changes in the November 2003-March 2004 period were from M vent, where the iron concentrations dropped by one-third over this time period. The drop in iron is likely related to the (smaller) increase in the concentration of hydrogen sulfide in these same vent fluids. Fe concentrations are likely controlled by the solubility of Fe-S minerals such as pyrite (FeS₂), which is dependent on the activity of sulfide squared. Hence relatively small changes in hydrogen sulfide can result in much larger changes in iron concentrations. While no significant temperature changes were noted in the vent fluids from the point measurements in November 2003 vs. March 2004, records from the recording temperature probes show an ~7°C temperature rise in the Bio9" fluids in late November 2003. The M vent fluids show an ~4°C temperature decrease lasting less than a day in March 2004, which occurs within 24 hours of another earthquake swarm. In most cases the changes in the fluid chemistry from November 2003-March 2004 are significantly smaller than those observed between February 2002 and November 2003. Correlations between variations (or lack thereof) in the fluid compositions and temperatures will be discussed relative to the seismic record.
DE: 3017 Hydrothermal systems (0450, 1034, 3616, 4832, 8135, 8424)
DE: 3035 Midocean ridge processes
DE: 3075 Submarine tectonics and volcanism
DE: 4832 Hydrothermal systems (0450, 1034, 3017, 3616, 8135, 8424)
DE: 4835 Marine inorganic chemistry (1050)
SC: Tectonophysics [T]
MN: Fall Meeting 2005