Experimental investigation of the Peierls stress of olivine at high pressures using the deformation-DIA
Abstract
The rheological behavior of the lithospheric mantle plays an important role in plate tectonics. However, due to the limitation of technology, the rheological properties of the lithosphere are rather poorly constrained. To date, experimental constraints on the low-temperature plasticity of lithospheric rocks arise mainly either from micro- indentation experiments [e.g., Evans and Goetze, 1979] or from stress relaxation experiments [Raterron et. al, 2004]. Both of these approaches have limitations in terms of developing a flow law that approximates steady state deformation. To further define the low-temperature, high-stress behavior of mantle rocks, we are conducting high-pressure experiments on dunite aggregates using a deformation-DIA apparatus at a synchrotron beamline. Samples were hot-pressed from mixtures of powder of olivine plus 5% enstatite. Samples 1 mm in length x 1.1 mm in diameter were encapsulated with 0.025-mm thick Ni foil and assembled with alumina piston, a boron nitride sleeve, and graphite resistance heater into a 6-mm edge length cubic pressure medium. After a cell is pressurized isotropically to a predetermined level and heated to run temperature, the sample is deformed in triaxial compression. X-ray diffraction patterns were used to determine pressure (i.e., mean stress) and differential stress from the strain of various lattice planes measured as a function of orientation with respect to the applied stress field. Sample strain is computed from the length change of deforming samples measured from a series of x-radiographic images. We have explored the rheological properties of our dunite samples at stresses up to {~} 3 GPa and temperatures of 673 and 873K. Our initial results differ from those reported in previous studies. The strength of our sample deformed at 673 K is somewhat lower than that predicted by the flow laws of Evans and Goetze and Raterron et al., the strength of our sample deformed at 873 K is somewhat higher than that predicted by either flow law. Experiments are in progress to further delineate the rheological behavior of olivine at low temperatures and high differential stresses.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMMR11B0140M
- Keywords:
-
- 3902 Creep and deformation;
- 3924 High-pressure behavior;
- 5120 Plasticity;
- diffusion;
- and creep;
- 8120 Dynamics of lithosphere and mantle: general (1213);
- 8159 Rheology: crust and lithosphere (8031)