HR: 1340h
AN: T23B-1407    [Abstracts]
TI: Hydrothermal Circulation across the Axis of (Slow-Spreading) Mid-Ocean Ridges: the Role of Faults and Variations in Lithospheric thickness.
AU: * FONTAINE, F J
EM: fontaine@ipgp.jussieu.fr
AF: IPGP-Geosciences Marines, 4 place Jussieu Boite 89, Paris, 75252, France
AU: Cannat, M
EM: cannat@ipgp.jussieu.fr
AF: IPGP-Geosciences Marines, 4 place Jussieu Boite 89, Paris, 75252, France
AU: Escartin, J
EM: escartin@ipgp.jussieu.fr
AF: IPGP-Geosciences Marines, 4 place Jussieu Boite 89, Paris, 75252, France
AB: The permeable (and thermal) structure(s) of mid-ocean ridges control the dynamics, distribution and geometry of sub-seafloor hydrothermal circulations. Ridge perpendicular extension likely leads to faulting and a permeability that is strongly anisotropic favoring along-axis flow. Across-axis flow can not be ruled out, especially at slow- spreading mid-ocean ridges where the lithosphere is crossed cut by ridge-parallel faults that can root near the magma chamber as recently evidenced by Singh et al. (2006) on the mid-Atlantic ridge at the Lucky Strike site. It may thus be that hydrothermal flow at slow spreading ridges has a significant across-axis component. The dynamical pattern of this across-axis flow critically depends on (i) the across-axis permeability and temperature structures and (ii) the characteristics of the fault system (e.g., fault location, dipping angle, interconnection and hydraulic properties). In this communication we study the characteristics of this across-axis flow by means of numerical models of hydrothermal circulation. The models incorporate realistic fluid properties, permeability (i.e., layered versus homogeneous systems) and thermal (i.e., variations in across-axis thickness of the brittle lithosphere) structures. As it has been proposed that faults can be both permeable conduits and impermeable barriers, and that the hydraulic properties may be transient, we model the effects of both enhanced and reduced fault zone permeability. The different fault models provide insight on possible temperature and geometry (e.g., cell aspect ratio, coupling of fluid flow between faults) of the hydrothermal circulation, and help constrain the role of fault systems in focusing hot or cold fluid flows and their possible contribution to the general sub-seafloor hydrothermal circulation.
DE: 3225 Numerical approximations and analysis (4260)
DE: 8135 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8424)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting