Viscoelasticity of partially molten rocks at mantle P-T
Abstract
The mechanical properties of a partially molten rock are crucial for interpreting the attenuation and velocities of seismic waves. While partial melting is often associated with low seismic shear wave velocity zone (LVZ) (Anderson and Sammis, 1970); studies have also suggested that partial melting may not be required to interpret the large velocity variation in the upper mantle (Faul and Jackson, 2005; Karato and Jung, 1998; Stixrude and Lithgow-Bertelloni, 2005). Extensive studies (Faul et al., 2004; Gribb and Cooper, 2000; Jackson et al., 2004) have been carried out on the attenuation behavior of partially-molten samples using melt-bearing olivine sample but at low-pressure (less than 300 MPa). Our recent developments (Li and Weidner, 2007) have allowed us to study energy dissipation in materials at high P-T (up to 15 GPa-2000K) and seismic frequencies. We have performed some experiments to characterize attenuation and dispersion in a model mantle composition (Kilborne Hole peridotite nodule, KLB- 1) at 1-10 GPa pressures. We use the multi-anvil high pressure device D-DIA (Durham et al., 2002; Wang et al., 2003) coupled with synchrotron X-ray radiation (Weidner et al., 2005). Mechanical testing is done by applying a uniaxial forced oscillation on a sample typically of 1 mm length and 1-1.5 mm diameter. The preliminary results raised many interesting issues. The detected Q and Young's modulus were found to be dependent on the pre-annealing conditions of the sample which may be a result of unrelaxed differential stresses. The geometry of the melted phases highly depends on the magnitude of the stress and melt- fractions. Microscopic analysis of the recovered sample will also be discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMMR43A1804W
- Keywords:
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- 3909 Elasticity and anelasticity;
- 3924 High-pressure behavior;
- 3954 X-ray;
- neutron;
- and electron spectroscopy and diffraction;
- 4465 Phase transitions;
- 8162 Rheology: mantle (8033)