Transcript F. Heidelbach - TU Bergakademie Freiberg

Orientation mapping with high energy X-rays
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X-ray energy > 50keV
increased penetration depth (up to cm)
probing of grain structure in 3D
resolution along the beam by ray
tracing or conical slits down to 10s of mm
• additional rotation is needed for complete
orientation of single grains
Margulies et al. 2001
Science 291, 2392
Poulsen et al. 1997
J. Sync. Rad. 4, 147
Following grain rotations during deformation in-situ
• deformation of polycrystalline Al in tension
• orientation changes are followed in-situ
• broadening of peaks due to intracrystalline
defects
• rotations are inconsistent
with both Taylor and Sachs
models of deformation
Margulies et al. 2001
Texture analysis in experimentally deformed rocks:
Deformation geometries and apparatus
• Paterson apparatus: pressure medium gas (Ar):
p ~ 500 MPa, T ~ 1600 K, s ~ 200 MPa
• Griggs rig: solid medium (NaCl):
p ~ 5 GPa, T ~ 2000 K, s ~ 1500 MPa
Deformation geometries
• axial compression
(• axial extension)
(• extrusion)
• direct shear
• torsion
Magnesiowüstite in axial compression (e = 30%)
Map of microstructure, stepwidth 2mm
green: {110} parallel to compression axis
blue: {100} parallel to compression axis
red: boundaries with misorientations > 1°
Black lines
Red lines
Pole figures
Misorientation histogram
Stretton et al. 2001,
Earth Planet. Sci. Lett.194, 229
Axial compression and direct shear of quartz aggregates
e = 54%
g = 2.1
g = 2.4
Dell‘Angelo & Tullis 1989, Tectonophysics 169, 1
Direct shear experiments of polycrystalline albite
• Deformation of albite in
simple shear: g up to ~ 11
<-300mm->
X-ray spectrum