HR: 1340h
AN: B13A-0210    [Abstracts]
TI: Numerical Modelling of MOR Hydrothermal Systems: The Need to Use Compressible Fluids, Realistic EOS and High-resolution Meshes
AU: * Coumou, D
EM: coumou@erdw.ethz.ch
AF: ETH Zurich, Isotope Geochemistry and Mineral Resources Department of Earth Sciences Sonnegstrasse 5 , Zurich, 8092 Switzerland
AU: Geiger, S
EM: geiger@erdw.ethz.ch
AF: ETH Zurich, Isotope Geochemistry and Mineral Resources Department of Earth Sciences Sonnegstrasse 5 , Zurich, 8092 Switzerland
AU: Driesner, T
EM: driesner@erdw.ethz.ch
AF: ETH Zurich, Isotope Geochemistry and Mineral Resources Department of Earth Sciences Sonnegstrasse 5 , Zurich, 8092 Switzerland
AU: Heinrich, C
EM: heinrich@erdw.ethz.ch
AF: ETH Zurich, Isotope Geochemistry and Mineral Resources Department of Earth Sciences Sonnegstrasse 5 , Zurich, 8092 Switzerland
AB: We use a simplified model of convection in a porous medium to investigate the transport of mass and energy in sub-seafloor hydrothermal systems with high permeabilities. Previous studies have addressed the issue either taking the Boussinesq approximation and/or using too coarse meshes. Here we argue that both steps result in erroneous results and typically lead to artificial and non-realistic steady state solutions. The highly non-linear thermodynamic properties of water cause plumes to form around temperatures of 400$^\circ$C where energy transport is maximised. This cannot be modelled accurately using a hypothetical Boussinesq fluid for which the variations in fluid properties are linearized. Further we show that high-resolution meshes are essential in representing the full dynamics of the system. Coarse meshes tend to suppress density instabilities and result in non-realistic steady-state solutions. When using high-resolution meshes the convection pattern will remain non-steady. Based on our recent simulations of convection of H$_2$O-NaCl liquid+vapor fluid mixtures around granitic intrusions, we expect that convection patterns for seawater compositions will be even more unstable.
DE: 8424 Hydrothermal systems (8135)
DE: 3015 Heat flow (benthic) and hydrothermal processes
DE: 3035 Midocean ridge processes
DE: 3220 Nonlinear dynamics
DE: 3230 Numerical solutions
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting