Fig. 3. 3D X-ray microtomography image of 75% neighborite ... · data collected at beamline 2-BM at...
1
0 50 100 150 200 250 300 1.28 1.85 2.42 2.98 3.55 4.12 4.68 5.25 5.82 6.38 Undeformed 75% Neighborite 75% Neighborite 25% Neighborite Two-phase deformation of lower mantle mineral analogs Pamela Kaercher 1 , Lowell Miyagi 2 , Waruntorn Kanitpanyacharoen 1 , Eloisa Zepeda-Alarcon 1 , Yangbin Wang 3 , Francesco De Carlo 3 , Hans-Rudolph Wenk 1 1 Department of Earth and Planetary Science, University of California, Berkeley, CA ∙ 2 Department of Geology and Geophysics, The University of Utah, Salt Lake City, UT ∙ 3 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois Introduction While much is known about preferred orientation in single phase aggregates, deformation of polyphase materials is still enigmatic. Most of the Earth is composed of polymineralic rocks, including the lower mantle which is of critical importance for understanding the geodynamic evolution of the planet. Of the few studies which have examined deformation in mantle mineral composites (e.g. Li et al. 2007), none have examined lattice preferred orientation. D-DIA Microtomography 0.06 mm NaCl grain Conclusion Undeformed Deformed Neighborite (NaMgF 3 ) Halite (NaCl) 0.1 mm 1 Process raw tiff images to create slices 2 Threshold each phase out by selecting its intensity range 3 Post-processed with opening algorithm to bring out grains 4 Smoothed using non- local means algorithm to reduce noise 75% neighborite 25% halite 5 Select a subset of data Samples were deformed in the D-DIA at APS. Sintered cylinders of various volume fractions of the two phases were compressed then stressed uniaxially. Diffraction patterns were collected in situ up to approximately 4 GPa, 800°C , and 50% strain in order to observe evolution of preferred orientation. The Rietveld method as implemented in the software package MAUD was applied to identify phases and quantify preferred orientation. Initial results from D-DIA experiments show that texture strength in neighborite increases with decreasing halite content. This suggests that the softer phase, NaCl, absorbs much of the deformation. Interestingly texture of halite is very weak as if hard particles enforce strain shadows and cause local heterogeneity. Pores 25% neighborite 75% halite 25% NaMgF 3 75% NaCl 50% NaMgF 3 50% NaCl 75% NaMgF 3 25% NaCl 100% NaMgF 3 m.r.d. 0.80 – 1.26 m.r.d 0.00 – 4.89 m.r.d. 0.52 – 1.53 Neighborite Halite m.r.d: 0.16-2.46 m.r.d 0.70 – 1.56 m.r.d 0.00 – 4.94 m.r.d. 0.00 – 9.19 (Mg,Fe) O Mg Si O Pressure (GPa) Depth (km) (Mg,Fe) 2 SiO 4 (Mg,Fe) 2 SiO 4 (Mg,Fe) 2 SiO 4 (Mg,Fe)O + (Mg,Fe)SiO 3 Ringwoodite Olivine Wadsleyite Ferropericlase + Mg-perovskite During deformation, is the minor, weak phase isolated in pockets and grain boundary junctions so that the bulk deformation has to occur in the hard phase? Or does the soft phase lubricate grain boundaries so that it concentrates deformation, and the hard phase moves as rigid blocks? The lower mantle is composed primarily of two mineral phases: Solid lines are slip planes. (a) uniaxial stress is applied causing (b) shear deformation. (c) slip plane normal rotates toward the compression direction. a b c σ 11 σ 11 β β α Lattice rotation leads to lattice preferred orientation and seismic anisotropy Weak Stiff K = 160 GPa K = 246 GPa Ferropericlase Mg-perovskite Since lower mantle conditions are beyond the capabilities of D-DIA, we used neighborite (NaMgF 3 ) as the hard phase analog of magnesium-silicate perovskite (Zhao et al. 1993; Liu et al. 2005) and halite (NaCl) as the soft phase analog of ferropericlase. Isostructural to (Mg,Fe)SiO 3 Isostructural to (Mg,Fe)O Neighborite (NaMgF 3 ) Same slip systems as (Mg,Fe)O: {110}<1-10>, {111}<1-10>, {100}<1-10> Possible slip systems of (Mg,Fe)SiO 3 : (001),(010)[100],(100) [010] x y z (110) plane <1-10> direction 1 2 3 1 2 3 Halite (NaCl) of NaMgF 3 : {1-10}<110>, (001)<100> X-rays Detector Sample 2D plot for 75% NaMgF 3 + 25% NaCl. Curviness of lines shows degree of elastic strain. Halite curves are straighter suggesting that it absorbs the deformation. Change in intensity with azimuthal angle denotes plastic strain resulting in lattice preferred orientation. 100 010 001 111 010 001 Unrolled spectrum for 75% NaMgF 3 + 25% NaCl Dotted blue line is collected data. Solid black line is calculated fit. NaCl 200 NaCl 220 0.06 mm 0.06 mm Compression direction NaMgF 3 grain aspect ratios Inverse pole figures for neighborite-halite mixtures compressed to 3 GPa, deformed to 15% strain and heated to 400 °C in D-DIA, illustrating the effect of volume fractions on texture strength. Initial results from D-DIA experiments show that texture strength in neighborite increases with decreasing halite content. This suggests that the softer phase, NaCl, absorbs much of the deformation. Interestingly texture of halite is very weak as if hard particles enforce strain shadows and cause local heterogeneity. Microtomography data collected at beamline 2-BM at the APS supports this. Processed tomography data for a deformed sample of 75% NaMgF 3 + 25% NaCl shows that soft halite surrounds the harder grains of neighborite. These preliminary findings are very encouraging and experiments, both on texture and microstructure are being continued. Further experiments and FEM modeling (Quey et al. 2011) will be done in order to accurately quantify the contribution of each mineral phase to the final texture of the composite. These results can then be input into models of the lower mantle (e.g. Wenk et al. 2011) to improve our understanding Earth’s geodynamics. Acknowledgements We thank CDAC for financial support and APS for the use of beamlines 13-BM-D and 2-BM-XOR. References Li L, Addad A, Weidner D, Long H, Chen J (2007). Tectonophysics 439:107-117. Liu HZ, Chen J, Hu J, Martin CD, Weidner DJ, Hausermann D, Mao HK (2005). Geophy. Res. Lett. 32, doi: 10.1029/2004GL022068. Quey R, Dawson P, Barbe F (2011). Comput. Methods Appl. Mech. Engrg., 200:1729-1745. Wenk HR, Cottaar S, Tomé C, McNamara A, Romanowicz B (2011). EPSL-10860. Zhao Y, Weidner DJ, Parise JB, Cox DE (1993). PartI. Phys. Earth Planet. Inter., 76:1-16. 75% neighborite 25% halite Halite grains (shown in green) surround the neighborite grains (gray). Orthoslices in the XZ plane showing initial and deformed grains . 0 20 40 60 80 100 120 140 1.28 1.85 2.42 2.98 3.55 4.12 4.68 5.25 5.82 6.38 Undeformed 75% Neighborite 75% Neighborite 25% Neighborite NaCl grain aspect ratios Fig. 3. 3D X-ray microtomography image of 75% neighborite-25% halite illustrating local deformation and connectivity. The edge of the cube is 0.1 mm. Blue is halite. Histograms showing aspect ratios for neighborite and halite grains. There are a greater number of grains with an aspect ratio ≈1 in the undeformed sample, but a great number of grains with larger aspect ratios in the deformed samples. Aspect ratio Aspect ratio Number of grains Number of grains Analog Minerals Microtomography of one undeformed and two deformed samples was performed at beamline 2-BM of the APS. Raw images where processed first in Octopus software to produce orthoslices, then in Avizo Fire to create 2D and 3D rendering of the sample and grain statistics which are shown below. Halite grains were a slightly lighter shade of gray due to having a slightly higher atomic number than neighborite and thus greater absorption. 10000 Intensity/counts Number of voxels 18750 27500 36250 45000 20000 40000 60000 80000 0 pores halite neighborite 0.1 mm 0.1 mm 0.1 mm 0.1 mm 0.1 mm 0.1 mm 0.5 mm 0.5 mm 0.25 mm NaCl 200 NaCl 220 NaMgF 3 NaMgF 3 NaCl 111 ? NaMgF 3 021 NaMgF 3 101 NaMgF 3 110 2-Theta (degrees) Intensity/counts (log scale) 2.2 2.0 1.8 1.6 4.0 6.0 8.0 4.0 6.0 8.0 NaCl 111 NaMgF 3 180 180 2-Theta (degrees) NaMgF 3 101 Azimuthal angle (degres) 0 0 Data Fit artifacts
Transcript of Fig. 3. 3D X-ray microtomography image of 75% neighborite ... · data collected at beamline 2-BM at...
0
50
100
150
200
250
300
1.28 1.85 2.42 2.98 3.55 4.12 4.68 5.25 5.82 6.38
Undeformed 75% Neighborite
75% Neighborite
25% Neighborite
Two-phase deformation of lower mantle mineral analogs Pamela Kaercher1, Lowell Miyagi2, Waruntorn Kanitpanyacharoen1, Eloisa Zepeda-Alarcon1, Yangbin Wang3,
Francesco De Carlo3, Hans-Rudolph Wenk1
1Department of Earth and Planetary Science, University of California, Berkeley, CA ∙ 2Department of Geology and Geophysics, The University of Utah, Salt Lake City, UT ∙ 3Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois
Introduction While much is known about preferred orientation in single phase aggregates, deformation of polyphase materials is still enigmatic. Most of the Earth is composed of polymineralic rocks, including the lower mantle which is of critical importance for understanding the geodynamic evolution of the planet. Of the few studies which have examined deformation in mantle mineral composites (e.g. Li et al. 2007), none have examined lattice preferred orientation.
D-DIA
Microtomography
0.06 mm
NaCl grain
Conclusion
Undeformed Deformed
Neighborite (NaMgF3)
Halite (NaCl)
0.1 mm
1 Process raw tiff
images to create slices
2
Threshold each phase out by selecting its
intensity range
3
Post-processed with opening algorithm to
bring out grains
4
Smoothed using non-local means algorithm
to reduce noise 75% neighborite 25% halite
5
Select a subset of data
Samples were deformed in the D-DIA at APS. Sintered cylinders of various volume fractions of the two phases were compressed then stressed uniaxially. Diffraction patterns were collected in situ up to approximately 4 GPa, 800°C , and 50% strain in order to observe evolution of preferred orientation.
The Rietveld method as implemented in the software package MAUD was applied to identify phases and quantify preferred orientation. Initial results from D-DIA experiments show that texture strength in neighborite increases with decreasing halite content. This suggests that the softer phase, NaCl, absorbs much of the deformation. Interestingly texture of halite is very weak as if hard particles enforce strain shadows and cause local heterogeneity.
Pores
25% neighborite 75% halite
25% NaMgF3 75% NaCl
50% NaMgF3 50% NaCl
75% NaMgF3 25% NaCl
100% NaMgF3
m.r.d. 0.80 – 1.26
m.r.d 0.00 – 4.89
m.r.d. 0.52 – 1.53
Neighborite
Halite
m.r.d: 0.16-2.46
m.r.d 0.70 – 1.56
m.r.d 0.00 – 4.94 m.r.d. 0.00 – 9.19
(Mg,Fe) O
Mg Si O
Pressure (GPa)
Depth (km)
(Mg,Fe)2SiO4 (Mg,Fe)2SiO4 (Mg,Fe)2SiO4 (Mg,Fe)O + (Mg,Fe)SiO3 Ringwoodite Olivine Wadsleyite Ferropericlase + Mg-perovskite
During deformation, is the minor, weak phase isolated in pockets and grain boundary junctions so that the bulk deformation has to occur in the hard phase? Or does the soft phase lubricate grain boundaries so that it concentrates deformation, and the hard phase moves as rigid blocks?
The lower mantle is composed primarily of two mineral phases:
Solid lines are slip planes. (a) uniaxial stress is applied causing (b) shear deformation. (c) slip plane normal rotates toward the compression direction.
a b c
σ11 σ11
β
β α
Lattice rotation leads to lattice preferred orientation and seismic anisotropy
Weak Stiff K = 160 GPa K = 246 GPa
Ferropericlase Mg-perovskite
Since lower mantle conditions are beyond the capabilities of D-DIA, we used neighborite (NaMgF3) as the hard phase analog of magnesium-silicate perovskite (Zhao et al. 1993; Liu et al. 2005) and halite (NaCl) as the soft phase analog of ferropericlase.
Isostructural to (Mg,Fe)SiO3 Isostructural to (Mg,Fe)O
Neighborite (NaMgF3)
Same slip systems as (Mg,Fe)O: {110}<1-10>, {111}<1-10>, {100}<1-10>
Possible slip systems of (Mg,Fe)SiO3 : (001),(010)[100],(100) [010]
x
y
z (110) plane
<1-10> direction
1
2
3
1
2
3
Halite (NaCl)
of NaMgF3 : {1-10}<110>, (001)<100>
X-rays
Detector Sample
2D plot for 75% NaMgF3 + 25% NaCl. Curviness of lines shows degree of elastic strain. Halite curves are straighter suggesting that it absorbs the deformation. Change in intensity with azimuthal angle denotes plastic strain resulting in lattice preferred orientation.
100
010 001
111
010 001
Unrolled spectrum for 75% NaMgF3 + 25% NaCl Dotted blue line is collected data. Solid black line is calculated fit.
NaCl 200
NaCl 220
0.06 mm
0.06 mm
Compression direction
NaMgF3 grain aspect ratios
Inverse pole figures for neighborite-halite mixtures compressed to 3 GPa, deformed to 15% strain and heated to 400 °C in D-DIA, illustrating the effect of volume fractions on texture strength.
Initial results from D-DIA experiments show that texture strength in neighborite increases with decreasing halite content. This suggests that the softer phase, NaCl, absorbs much of the deformation. Interestingly texture of halite is very weak as if hard particles enforce strain shadows and cause local heterogeneity. Microtomography data collected at beamline 2-BM at the APS supports this. Processed tomography data for a deformed sample of 75% NaMgF3 + 25% NaCl shows that soft halite surrounds the harder grains of neighborite. These preliminary findings are very encouraging and experiments, both on texture and microstructure are being continued. Further experiments and FEM modeling (Quey et al. 2011) will be done in order to accurately quantify the contribution of each mineral phase to the final texture of the composite. These results can then be input into models of the lower mantle (e.g. Wenk et al. 2011) to improve our understanding Earth’s geodynamics.
Acknowledgements We thank CDAC for financial support and APS for the use of beamlines 13-BM-D and 2-BM-XOR.
References Li L, Addad A, Weidner D, Long H, Chen J (2007). Tectonophysics 439:107-117. Liu HZ, Chen J, Hu J, Martin CD, Weidner DJ, Hausermann D, Mao HK (2005). Geophy. Res. Lett. 32, doi:
10.1029/2004GL022068. Quey R, Dawson P, Barbe F (2011). Comput. Methods Appl. Mech. Engrg., 200:1729-1745. Wenk HR, Cottaar S, Tomé C, McNamara A, Romanowicz B (2011). EPSL-10860. Zhao Y, Weidner DJ, Parise JB, Cox DE (1993). PartI. Phys. Earth Planet. Inter., 76:1-16.
75% neighborite 25% halite
Halite grains (shown in green) surround the neighborite grains (gray).
Orthoslices in the XZ plane showing initial and deformed grains .
0
20
40
60
80
100
120
140
1.28 1.85 2.42 2.98 3.55 4.12 4.68 5.25 5.82 6.38
Undeformed 75% Neighborite
75% Neighborite
25% Neighborite
NaCl grain aspect ratios
Fig. 3. 3D X-ray microtomography image of 75% neighborite-25% halite illustrating local deformation and connectivity. The edge of the cube is 0.1 mm. Blue is halite.
Histograms showing aspect ratios for neighborite and halite grains. There are a greater number of grains with an aspect ratio ≈1 in the undeformed sample, but a great number of grains with larger aspect ratios in the deformed samples.
Aspect ratio Aspect ratio
Num
ber o
f gra
ins
Num
ber o
f gra
ins
Analog Minerals
Microtomography of one undeformed and two deformed samples was performed at beamline 2-BM of the APS. Raw images where processed first in Octopus software to produce orthoslices, then in Avizo Fire to create 2D and 3D rendering of the sample and grain statistics which are shown below.
Halite grains were a slightly lighter shade of gray due to having a slightly higher atomic number than neighborite and thus greater absorption.
10000 Intensity/counts
Num
ber o
f vox
els
18750 27500 36250 45000
20000
40000
60000
80000
0
pores
halite neighborite
0.1 mm
0.1 mm
0.1 mm
0.1 mm 0.1 mm 0.1 mm
0.5 mm
0.5 mm
0.25 mm
NaCl 200
NaCl 220
NaMgF3
NaMgF3 NaCl 111
?
NaMgF3
021
NaMgF3
101
NaMgF3
110
2-Theta (degrees)
Inte
nsit
y/co
unts
(log
sca
le)
2.2
2.0
1.8
1.6
4.0 6.0 8.0 4.0 6.0 8.0
NaCl 111 NaMgF3
180
180
2-Theta (degrees)
NaMgF3
101
Azi
mut
hal a
ngle
(deg
res)
0
0
Dat
a Fi
t
artifacts
