Poster Abstract Title: 
Preliminary model of hydrothermal circulation at East Pacific Rise 9°50 N constrained by thermal, chemical, and seismic data
Authors and their affiliations: 
Farough, A.; Lowell, R.P - Department of Geosciences, Virginia Tech, Blacksburg, VA 24061

The East Pacific Rise 9°50¢ N area has been a subject of intense multidisciplinary study for two decades. Currently, numerous data sets provide strong constraints on magmatic activity, on the depth and flow geometry of hydrothermal circulation, on the thermal and chemical evolution of vent fluids, and on the evolution of biological communities. These data together provide strong constraints on acceptable mathematical models of the magma-hydrothermal system. 

Using a combination of thermal, geochemical and seismic data as constraints [1,2,3], we develop a preliminary model hydrothermal circulation along approximately 2 km of ridge axis from TWP to the Bio9 vent complex. We first use a single-pass model [4] together with a heat flux estimate of 160MW and average vent temperature of 370°C to obtain a mass flux of » 80 kg/s, a conductive boundary layer thickness of » 10 m, and a permeability of the discharge zone ranging between 3 x10-12 and 3 x 10-13 m2. Secondly, we use a two-limb single-pass model using the observed partitioning of heat flow between focused and diffuse discharge [5] and vent chemistry [2] to show that at least 80% of the total heat flow comes from magma sources. As a result of these analyses, we find that the sub-axial magma chamber must be actively replenished on a decadal time scale, which is consistent with recent petrological data. Finally, the preliminary model suggests that the seismically inferred recharge zone may not be large enough to carry all the flow without clogging as a result of anhydrite precipitation. Further analysis of this issue will require numerical modeling.

  1. Ramondenc et al. (2006) EPSL, 245, 487-497.
  2. Von Damm and Lilley (2004) Geophys. Monogr. 144, 245-268.
  3. Tolstoy et al. (2008) Nature, 451, 181-184.
  4. Lowell and Germaonvich (2004) Geophys. Monogr. 148, 219-244.
  5. Germanovich et al. (2010)  J. Geophys. Res.
Contributions to Integration and Synthesis: 
The global importance of seafloor hydrothermal processes and the interplay among magma transport, crustal structure, seawater circulation, and biogeochemical processes have resulted in focused research at a few integrated study sites, through a number of coordinated, integrated, interdisciplinary experiments to develop focused, quantitative, whole system models for these sites.One of these sites is the 9°10 N region of the East Pacific Rise (EPR), particularly near 9°50 N.We model hydrothermal circulation at the East Pacific Rise ISS site.