HR: 14:55h
AN: DI43A-06    [Abstracts]
TI: Slabs Dehydration in the Earth's Mantle Transition Zone
AU: * RICHARD, G C
EM: guillaume.richard@yale.edu
AF: Dept of Geology and Geophysics Yale University, PO Box 208109, New Haven, CT 06520 United States
AU: Bercovici, D
EM: david.bercovici@yale.edu
AF: Dept of Geology and Geophysics Yale University, PO Box 208109, New Haven, CT 06520 United States
AU: KARATO, S
EM: shun-ichiro.karato@yale.edu
AF: Dept of Geology and Geophysics Yale University, PO Box 208109, New Haven, CT 06520 United States
AB: The water content of the Earth's mantle transition zone is the foundation of several global mantle dynamics models. Because of the high water solubility in Wadsleyite and Ringwoodite, the transitionzone is a potentially a large water reservoir of the deep Earth. Nevertheless, to keep the transition zone wet, the tendency for convection to distribute water over the entire mantlehas to offset by other mechanisms. One such mechanism could be linked to the slab dehydration process, caused by diffusion facilitated by the variation of water solubility with temperature. We have addressed how this effect influences slab water transport into the transition zone by developing a simple mathematical model of water diffusion. Numerical solution of the coupled (temperature and concentration) system of equations demonstrates that water concentration is essentially diffusivity dependent, solubility effect being lowered by the coupling. If standard-state chemical potential of water in transition zone mineral is assumed to be negative, it displays specific features in which water concentration increases below the slab edge and decrease above. This effect is likely to facilitate the reach of the solubility limit and thus fluid exsolution (hydrous melt or aqueous silicated fluid). To summarize, this effect is shown to imply that simple flux computation (without T-coupling) are relatively robust and that super-saturated area formation at the edge of a subducted slab are possible in the transition zone.
DE: 0560 Numerical solutions (4255)
DE: 3225 Numerical approximations and analysis (4260)
DE: 3611 Thermodynamics (0766, 1011, 8411)
DE: 4445 Nonlinear differential equations
SC: Study of Earth's Deep Interior [DI]
MN: Fall Meeting 2005