HR: 15:25h
AN: T33F-07 INVITED     [Abstracts]
TI: Shear-induced melt localization and the rheology of the partially molten mantle
AU: * Katz, R F
EM: katz@LDEO.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AU: Spiegelman, M
EM: mspieg@LDEO.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AU: Holtzman, B K
EM: benh@LDEO.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AB: The emergence of patterns of melt distribution in experiments on partially molten aggregates undergoing simple shear [1,2] provide a rare opportunity to test magma migration theory [3,4,5] by directly comparing experiments and calculations. The fundamental observation is the emergence and persistence to large strains of bands of high porosity and concentrated deformation oriented at about 15-25° to the plane of shear [6]. We have extended the analysis of Spiegelman [7] and report results from new linear analysis and numerical solutions that suggest that band angle in experiments is controlled by a balance between porosity and strain rate-weakening mechanisms. Lower angles are predicted for stronger strain rate-weakening. For the specific model considered here, a power-law stress-dependent rheology, calculations with n~6 are consistent with the observations. These results suggest that partially molten aggregates deforming under shear may have a greater sensitivity to strain rate than previously believed [8].
[1] Zimmerman, M. et al., Geophys. Res. Lett., 26, 1999.
[2]Holtzman, B. et al., Geochem. Geophys. Geosyst., 4, 2003.
[3]Mc{K}enzie, D., J. Petrol., 25, 1984.
[4]Fowler, A., Geophys. Astrophys. Fluid Dyn., 33, 1985.
[5]Bercovici, D. et al., J. Geophys. Res.- Solid Earth, 106, 2001.
[6]Spiegelman, M., Geochem. Geophys. Geosyst., 4, 2003.
[7]Holtzman, B. et al., J. Petrol., 2005.
[8]Hirth, G. and D. Kohlstedt, J. Geophys. Res., 100, 1995.
UR: http://www.LDEO.columbia.edu/~katz
DE: 0560 Numerical solutions (4255)
DE: 8145 Physics of magma and magma bodies
DE: 8162 Rheology: mantle (8033)
DE: 8178 Tectonics and magmatism
DE: 8434 Magma migration and fragmentation
SC: Tectonophysics [T]
MN: Fall Meeting 2005