Pressure-Induced Slip-System Transition in Forsterite: Single-Crystal Rheological Properties at Mantle Pressure and Temperature

Journal Article · Mon Jan 01 00:00:00 EST 2007 · American Mineralogist

DOI:https://doi.org/10.2138/am.2007.2474· OSTI ID:959614

Raterron, P; Chen, J; Li, L; Weidner, D; Cordier, P

Deformation experiments were carried out in a Deformation-DIA high-pressure apparatus (D-DIA) on oriented Mg2SiO4 olivine (Fo100) single crystals, at pressure (P) ranging from 2.1 to 7.5 GPa, in the temperature (T) range 1373-1677 K, and in dry conditions. These experiments were designed to investigate the effect of pressure on olivine dislocation slip-system activities, responsible for the lattice-preferred orientations observed in the upper mantle. Two compression directions were tested, promoting either [100] slip alone or [001] slip alone in (010) crystallographic plane. Constant applied stress ({sigma}) and specimen strain rates (Formula) were monitored in situ using time-resolved X-ray synchrotron diffraction and radiography, respectively. Transmission electron microscopy (TEM) investigation of the run products reveals that dislocation creep assisted by dislocation climb and cross slip was responsible for sample deformation. A slip transition with increasing pressure, from a dominant [100]-slip to a dominant [001]-slip, is documented. Extrapolation of the obtained rheological laws to upper-mantle P, T, and {sigma} conditions, suggests that [001]-slip activity becomes comparable to [100]-slip activity in the deep upper mantle, while [001] slip is mostly dominant in subduction zones. These results provide alternative explanations for the seismic anisotropy attenuation observed in the upper mantle, and for the 'puzzling' seismic-anisotropy anomalies commonly observed in subduction zones.

• 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: 959614
• Report Number(s): BNL-82600-2009-JA; AMMIAY; TRN: US1005760
• Journal Information: American Mineralogist, Vol. 92; ISSN 0003-004X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANISOTROPY
ATTENUATION
COMPRESSION
CREEP
DEFORMATION
DIFFRACTION
DISLOCATIONS
EXTRAPOLATION
MAGNESIUM SILICATES
MONOCRYSTALS
OLIVINE
PRESSURE RANGE GIGA PA
SLIP
STRAIN RATE
SUBDUCTION ZONES
TEMPERATURE RANGE 1000-4000 K
TRANSMISSION ELECTRON MICROSCOPY
national synchrotron light source