HR: 16:30h
AN: T14A-03 INVITED     [Abstracts]
TI: Thermodynamic Geodynamics: The Power of Volume Change
AU: * Regenauer-Lieb, K
EM: klaus.regenauer-lieb@csiro.au
AF: CSIRO Exploration and Mining, PO Box 1130, Bentley, WA 6982 Australia
AU: Morra, G
EM: morrag@student.ethz.ch
AF: ETH Zurich, Sonneggstrasse 5, Zurich, 8092 Switzerland
AU: Ruepke, L
EM: lars.rupke@fys.uio.no
AF: University of Oslo, PGP PO Box 1048, Oslo, 0316 Norway
AU: Morgan, J P
EM: jp369@cornell.edu
AF: Cornell University, 4164 Snee Hall, Ithaca, NY 14853 United States
AU: Yuen, D A
EM: davey@krissy.geo.umn.edu
AF: University of Minnesota, 23 Pillsbury Hall, Minneapolis, MN 55455-0219 United States
AU: Connolly, J
EM: james.connolly@erdw.ethz.ch
AF: ETH Zurich, Sonneggstrasse 5, Zurich, 8092 Switzerland
AB: We describe a fast instability mechanism which relies on the physics of feedback of thermal elasticity in continuity, momentum equilibrium as caused by the thermodynamic fluxes of a creeping solid. The mechanism relies on the volume change associated with a phase transformations, where the rate of reaction is dictated by the rate of creeping and the associated heating rate on the background of slow deformation of the solid.

We first stumbled across this PERPLEXing mechanism when combining thermal-mechanical subduction simulations with a free energy minimizer for controlling, thermodynamic properties of phase equilibria. In our models very high strain rates were observed during breakdown of serpentinite. While there exist important long term mechanical consequences of phase transitions, affecting slab dynamics, we focus here on the important consequences for fast time scale instabilities. The mechanism observed in our models is not a classical anti-crack mechanism. We observe the same mechanism in calculations whithout phase transitions. We find that thermal elastic volume changes can trigger thermal-mechanical instabilities along shear failure planes (Mode 2). The feedback mechanism is extremely powerful. It hence does not rely on the comparatively fast kinetics of phase transitions. We can isolate thermal elasticity, i.e. the elastic stress field of thermal expansion, as the basic mechanism. The finding opens new ways towards understanding the physics underlying deep earthquakes, kimberlites and other extreme lithospheric failure modes.
UR: http://www.geophysik.uni-mainz.de
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8122 Dynamics: gravity and tectonics
DE: 8159 Rheology: crust and lithosphere (8031)
SC: Tectonophysics [T]
MN: Fall Meeting 2005