HR: 0800h
AN: V51B-1476    [Abstracts]
TI: Mechanism of Serpentinization
AU: * Iyer, K H
EM: k.h.iyer@fys.uio.no
AF: Physics of Geological Processes, University of Oslo, P.O.Box 1048, Blindern Norway, Oslo, 0316 Norway
AU: Jamtveit, B
EM: bjorn.jamtveit@geologi.uio.no
AF: Physics of Geological Processes, University of Oslo, P.O.Box 1048, Blindern Norway, Oslo, 0316 Norway
AU: Podladchikov, Y Y
EM: y.y.podladchikov@fys.uio.no
AF: Physics of Geological Processes, University of Oslo, P.O.Box 1048, Blindern Norway, Oslo, 0316 Norway
AB: Serpentinite outcrops may be accompanied by cross-cutting fractures. In outcrops, the fractures observed in serpentinites appear to be spaced at regular intervals. We argue that hydration of the protolith during serpentinization can induce a volume increase (isochemical serpentinization) which in turn produces fractures. Opening mode fractures in a layered rock have been described in previous work to have a distinct spacing which depends on the thickness of the fractured layer and is described mechanically, but chemical reactions and changes in rheology have not been taken into account. Serpentinized rocks also display fracturing of the constituent grains at the microscopic scale. We describe the fractured serpentinite by means of a numerical model involving a viscoelastoplastic rock layer. The layer is isotropic and homogeneous. A wetting front is introduced which propagates through the layer. The fluid migrates into the system at a constant rate and is diffused throughout the media. When the fluid pressure is sufficiently high to overcome the body forces, the rock fractures. The permeability is increased in the fractures and the stresses acting upon the walls of the fracture are dropped to the yield threshold. Volume changes due to the reaction between fluid and rock are also taken into consideration and affect the local stresses. The fracture geometry is furthermore influenced by the changes in rock rheology that are induced during the phase transitions taking place during serpentinization.
DE: 3612 Reactions and phase equilibria (1012, 8412)
DE: 3617 Alteration and weathering processes (1039)
DE: 3660 Metamorphic petrology
DE: 5104 Fracture and flow
DE: 8020 Mechanics, theory, and modeling
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005