HR: 16:30h
AN: S22E-03    [PDF]
TI: Water Weakening of Clinopyroxene in the Dislocation Creep Regime
AU: * Chen, S
EM: chen0705@umn.edu
AF: University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455 United States
AU: Kohlstedt, D L
EM: dlkohl@umn.edu
AF: University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455 United States
AB: In our experimental studies, we investigated water weakening in the dislocation creep regime of natural Sleaford Bay clinopyroxenite containing diopside of compostion Ca$_{1.0}$Mg$_{0.8}$Fe$_{0.2}$Si$_{2}$O$_{6}$. Samples were deformed in a gas-medium apparatus at confining pressures of 300 to 400 MPa and temperatures of 1373 to 1498 K with the oxygen fugacity buffered by the solid state reaction between Ni and NiO. A small amount of free water was added to each sample to obtain water-saturated conditions. Based on results from compressive creep experiments on seven samples deformed under hydrous condition, coarse-grained natural clinopyroxene yielded a stress exponent of $n$ = 3.6$\pm$ 0.6 and an activation energy of $Q$ = 520$\pm$63KJ/mol. Compared to published data for dislocation creep of dry clinopyroxene, the wet aggregate flows up to 150 times faster at a given stress and temperature. Together with creep data for olivine, which show that olivine flows less than 10 times faster under hydrous condition than under anhydrous condition, the water weakening effect is much more significant in clinopyroxene than in olivine.
DE: 3902 Creep and deformation
DE: 3904 Defects
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8159 Rheology--crust and lithosphere
DE: 8162 Rheology--mantle
SC: Seismology [S]
MN: 2003 Fall Meeting