Experimental Constraints on the Strength of the Lithospheric Mantle
To provide a better understanding of rheological properties of mantle rocks under lithospheric conditions, we carried out a series of experiments on the creep behavior of polycrystalline olivine at high pressures ({approx}4-9 GPa), relatively low temperatures (673 {le} T {le} 1273 K), and anhydrous conditions, using a deformation-DIA. Differential stress and sample displacement were monitored in situ using synchrotron X-ray diffraction and radiography, respectively. Experimental results were fit to the low-temperature plasticity flow law. On the basis of this analysis, the low-temperature plasticity of olivine deformed under anhydrous conditions is well constrained by our data with a Peierls stress of {sigma}{sub P} = 5.9 {+-} 0.2 GPa, a zero-stress activation energy of E{sub k}(0) = 320 {+-} 50 kJ mol{sup -1}, and A{sub P} = 1.4 x 10{sup -7} s{sup -1} MPa{sup -2}. Compared with published results for high-temperature creep of olivine, a transition from low-temperature plasticity to high-temperature creep occurs at {approx}1300 K for a strain rate of {approx}10{sup -5} s{sup -1}. For a geological strain rate of 10{sup -14} s{sup -1}, extrapolation of our low-temperature flow law to 873 K, the cutoff temperature for earthquakes in the mantle, yields a strength of {approx}600 MPa. The low-temperature, high-stress flow law for olivine in this study provides a solid basis for modeling tectonic processes occurring within Earth's lithosphere.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- DOE - OFFICE OF SCIENCE
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 1019792
- Report Number(s):
- BNL-95638-2011-JA; JGREA2; TRN: US201115%%428
- Journal Information:
- Journal of Geophysical Research, Vol. 115; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
Similar Records
Rheology of the Deep Upper Mantle and its Implications for the Preservation of the Continental Roots: A Review
Deformation of Olivine at Mantle Pressure using D-DIA