HR: 08:00h
AN: T21D-01 INVITED     [Abstracts]
TI: The rheology of the subcontinental mantle
AU: * Hirth, G
EM: ghirth@whoi.edu
AF: WHOI, Department of Geology and Geophysics MS#8, Woods Hole, MA 02543 United States
AB: A combination of experimental data, geophysical observations, and microstructural analyses on naturally deformed mantle rocks can be used to constrain the rheological properties of the subcontinental mantle. With a concerted effort over the last 25 years or so, the rock mechanics community has now provided strong experimental constraints on the rheology of olivine aggregates at high temperature and pressure. The challenge now is to use these data, in conjunction with independent constraints on temperature and water content, to evaluate the conditions responsible for the stability and evolution of the subcontinental mantle, and to investigate what processes control the location of the base of the lithosphere. In this presentation, I will (1) Use deformation mechanism maps to illustrate how a combination of microstructural observations and rheological data constrain the conditions where a transition between dislocation creep and diffusion creep occurs in the mantle. (2) Analyze the competing effects of pyroxene content and dynamic recrystallization on controlling grain size, grain size evolution and viscosity of the continental mantle. (3) Discuss the implications of these constraints for interpreting observed seismic anisotropy. (4) Use a combination of diffusion data and grain growth kinetics to provide constraints necessary to interpret the sharpness and evolution of the base the lithosphere observed using both electrical and seismic techniques.
DE: 3615 Intra-plate processes (1033, 8415)
DE: 3902 Creep and deformation
DE: 3914 Electrical properties
DE: 5112 Microstructure
DE: 5120 Plasticity, diffusion, and creep
SC: Tectonophysics [T]
MN: Fall Meeting 2005