EastGRIP ice down to 2121m - fabric and microstructure

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EastGRIP ice down to 2121m - fabric and microstructure

EastGRIP Steering  Committee 2019

Ilka Weikusat & Nicolas Stoll 

Johanna Kerch, Ina Kleitz, Jan Eichler, Wataru Shigeyama, Tomoyuki Homma, Daniela Jansen, Maddalena Bayer-Giraldi, Ernst-Jan Kuiper, Julien Westhoff, Tomotaka Saruya, Sebastian Hellmann, Steven Franke, Pia Götz, Kumiko Goto-Azuma, Nobuhiko Azuma, Sérgio Henrique Faria, Sepp Kipfstuhl, Dorthe Dahl-Jensen

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F. Steinbach, Uni Tübingen

Introduction

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• Different planes in crystal è easiest deformation along basal plane (perpendicular to c-axis)

• C-axes projected as pole figures, core axis is represented through the centre of the circle

• Eigenvalues portray c-axis distribution as the three principal axes of an ellipsoid

After Hondoh (2000), 

displayed by Faria et al. (2014) I. Hewitt, course material Rheology of Ice

Moldflowinsight.com (2017)

Introduction

c-axis

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Introduction

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Introduction

Large Area  

Scanning Macroscope

1 cm

9.6 cm

Processed Data

• Grain shape & shape- preferred orientations

• Grain boundaries &

Sub-grain boundaries

• Grain-size

• Number of grains

• ^…

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A B

Introduction

Fabric Analyser  G50

Processed Data

• c-axes orientations

• Eigenvalues

• ^Woodcock

Parameter

• Grain-size

• Number of grains

• Subgrain structure

I. Hewitt, course material Rheology of Ice

1 cm

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0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Eigenvalue

Depth in m

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Eigenvalues

NEEM (Eichler, 2013, Montagnat, 2014)

GRIP (Thorsteinsson et al., 1997) EDML (Weikusat et al., 2017)

Studies before EGRIP 

e1 e2 e3

e1: Minimum

e2: Intermediate

e3: Maximum

Anisotropy

strain ellipsoid

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0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Eigenvalue

Depth in m

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Eigenvalues

EGRIP

e1 e2 e3

3000 m

e1: Minimum

e3: Maximum

Anisotropy

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0

200

400

600

800

1000

1200

1400

1600

1800

2000

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Eigenvalue

Depth in m

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Eigenvalues

2121 m

EGRIP

e1 e2 e3

e1: Minimum

e3: Maximum

• High-resolution data (full bag every 5-15m)

• 15 volume cuts (= 3x vertical + 2x horizontal)

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100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100

0.0 0.2 0.4 0.6 0.8

Eigenvalue

Depth in m

10

Eigenvalues

e1 e2 e3

Steven Franke, AWI

I. Hewitt, course material Rheology of Ice

EGRIP

= Horizontal section

e1: Minimum

e3: Maximum

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Steven Franke, AWI

Crystal preferred orientations

Combine diﬀerent scales

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Broad single

maximum Type I crossed girdle

symmetric Type I crossed girdle

asymmetric Developed girdle Strong girdle

Broad single Maximum

Developed Girdle

Strong Girdle Crossed Girdle

0 30

60

90

120

150 180 210 240 270

300 330

N = 755 427_1

0 30

60

90

120

150 180 210 240 270

300 330

N = 597 866_1

0 30

60

90

120

150 180 210 240 270

300 330

N = 596 1096_1

0 30

60

90

120

150 180 210 240 270

300 330

N = 1252 1377_1

0 30

60

90

120

150 180 210 240 270

300 330

N = 1091 1637_6

0 30

60

90

120

150 180 210 240 270

300 330

N = 891 2026_1

0 30

60

90

120

150 180 210 240 270

300 330

N = 1124 2475_4

0 30

60

90

120

150 180 210 240 270

300 330

N = 2165 2846_1

0 30

60

90

120

150 180 210 240 270

300 330

N = 2177 3117_6

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100

0.0 0.2 0.4 0.6 0.8

Eigen alue

Strong Girdle with   horizontal maxima

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100

0.0 0.2 0.4 0.6 0.8

Eigenvalue

Depth in m

Broad single

maximum Type I crossed girdle

symmetric Type I crossed girdle

asymmetric Developed girdle Strong girdle

e1: Minimum

e3: Maximum

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Kamb Contours C.I. = 2.0 Sigma Equal Area

Lower Hemisphere

N = 1468

Kamb Contours C.I. = 2.0 Sigma

Equal Area Lower Hemisphere

N = 2177

Thorsteinsson et al. (1997)

Paterson (1994)

Broad Single Maximum ->  

Vertical Compression from above

Girdle ->  

Extensional deformation

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Electron backscatter diﬀraction (EBSD) -> information about a-axes

Miyamoto et al. (2005)

c-axis

a-axes

After Hondoh (2000), 

displayed by Faria et al. (2014)

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c-axes a-axes

preliminary a-axes data for EGRIP at 1360 m 

M. Drury and D. Wallis, Utrecht University flow direction

• uniaxial extension and dominant basal slip

• hard orientation of slip-plane -> harder to deform

recrystallized grains (?) ->

larger resolved shear stress

The Arc, 2019

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Deformation modes

0m 196m

294m

500m

1150m

1260m

2121m

?

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100

300

500

700

900

1100

1300

1500

1700

1900

2100

0 2 4 6 8 10 12

Mean grain area in mm²

Depth in m

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Grain size

= Mean grain area of 

one thin section (400 - 4000 grains) Increase

Decrease

Increase Constant

Grain size variability

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Grain size

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100

0.0 2.5 5.0 7.5 10.0 12.5

Depth in m

NEEM EDML EGRIP

End of   last Glacial

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Grain size

100 300 500 700 900 1100 1300 1500 1700 1900 2100 2300 2500

0 50 100 150 200 250 300 350 400 450 500

Depth in m

100 300 500 700 900 1100 1300 1500 1700 1900 2100 2300 2500

0 5 10 15 20 25 30 35 40 45 50

Depth in m

NEEM EGRIP

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Grain size & crystal orientations

1 cm 2010 m

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Outlook - Micro-Cryo-Raman Spectroscopy

• Impurities influence physical properties of ice matrix 

-> lack of data regarding in-situ spatial distribution and incorporation of impurities

Eichler (2019)

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Outlook - Micro-Cryo-Raman Spectroscopy

Eichler (2019) C.Weikusat

• Micro-cryo-Raman spectroscopy on EastGRIP ice core + data about microstructure

• aim: to identify location, phase and composition of small inclusions

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0 2500 5000 7500 10000 12500 15000

546.7546.8546.9547.0547.1547.2547.3

Dust in ml

0 1 2 3

546.7546.8546.9547.0547.1547.2547.3

Conductivity

0 5 10 15 20 25

546.7546.8546.9547.0547.1547.2547.3

Ca

0 50 100 150 200 250

546.7546.8546.9547.0547.1547.2547.3

NH4

0 10 20 30

546.7546.8546.9547.0547.1547.2547.3Depth in m

Na

0.0 0.2 0.4 0.6

546.70

546.75

546.80

546.85

546.90

546.95

547.00

547.05

547.10

547.15

547.20

547.25

Eigenvalue

Depth in m

2.5 5.0 7.5 10.0 12.5

546.70

546.75

546.80

546.85

546.90

546.95

547.00

547.05

547.10

547.15

547.20

547.25

Mean grain area in mm^2

Outlook - Micro-Cryo-Raman Spectroscopy ²⁴

CFA/ICP-MS data by T. Erhardt & C. Jensen, Uni Bern Visual Stratigraphy by J. Westhoff, CIC

EGRIP bag 995 (546.7-547.25m)

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Thanks to everyone involved!

Questions?

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Weikusat et al. (2009)

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426 m 723 m

1361 m

Dynamic Recrystallisation

2093 m

1 cm

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Dynamic Recrystallisation

277 m 1 cm 338 m 1 cm

Passchier & Trouw (2005)

Dynamic

Recrystallisation

Urai et al. (1986)

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Grain size & crystal orientations

1 cm 1614 m

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bag 1346  29

739.78-740.3m

0e+00 2e+04 4e+04 6e+04 8e+04 1e+05

739.70739.75739.80739.85739.90739.95740.00740.05740.10740.15740.20740.25740.30

Dust in ml

0.0 0.5 1.0 1.5 2.0

739.70739.75739.80739.85739.90739.95740.00740.05740.10740.15740.20740.25740.30

Conductivity

0 5 10 15 20

739.70739.75739.80739.85739.90739.95740.00740.05740.10740.15740.20740.25740.30

Ca

0 10 20 30

739.70739.75739.80739.85739.90739.95740.00740.05740.10740.15740.20740.25740.30

NH4

0 5 10 15 20 25

739.70739.75739.80739.85739.90739.95740.00740.05740.10740.15740.20740.25740.30Depth in m

Na2

0.0 0.2 0.4 0.6

739.78

739.83

739.88

739.93

739.98

740.03

740.08

740.13

740.18

740.23

740.28

Eigenvalue

Depth in m

2.5 5.0 7.5 10.0 12.5

739.78

739.83

739.88

739.93

739.98

740.03

740.08

740.13

740.18

740.23

740.28

Mean grain area in mm^2

CFA/ICP-MS data by T. Erhardt & C. Jensen, Uni Bern Visual Stratigraphy by J. Westhoff, CIC

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Grain size

828 m 1444 m

Core breaks?

1 cm

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Perimeter Ratio

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700

0.70 0.75 0.80 0.85 0.90

Perimeter Ratio

Depth in m

Perimeter ratio = measure for grain irregularity

Weikusat et al. (2009)

Further down  to 2121 m?

EDML

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diﬀerent slip-systems influence diﬀerent parts of the crossed girdle

Passchier & Trouw (2005) Coaxial (pure shear)= principal axes of strain rotate

Non-Coaxial (simple shear) = strain

remain fixed with respect to the material

Van Der Pluijm and Marshak (2004)

->EBSD?

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After Schmid and Casey (1986) and Lister and Hobbs (1980), displayed by Vernooji (2005)

Schmid and Casey (1986)

Coaxialy deformed quartz:

- CPOs predicted by a theoretical model for dislocation glide -> based on the Taylor-Bishop-Hill analysis (Lister et al. 1978, Lister and Hobbs 1980) 

- These theoretical CPOs are supported by both experimental studies (Tullis et al. 1973, Tullis 1977) and analysis of naturally deformed quartzites (Price 1985, Schmid and Casey 1986)

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Kamb Contours C.I. = 2.0 Sigma

Equal Area Lower Hemisphere N = 1468 Kamb Contours C.I. = 2.0 Sigma

Equal Area Lower Hemisphere N = 891Kamb Contours C.I. = 2.0 Sigma

Equal Area Lower Hemisphere N = 574

118 m 196 m 234 m 241 m 289 m 328 m 398 m

After Schmid and Casey (1986) and Lister and Hobbs (1980),

displayed by Vernooji (2005)

- in many naturally deformed rocks, a spatial transition of

symmetrical crossed girdles to asymmetrical single girdles occurs

- related to an increasingly non-coaxial strain path

- this transition marks the bulk finite strain at which grains in

unfavourable orientations for continued intracrystalline slip are   1) partially substituted through grain boundary migration of more favourably oriented grains and  

2) partially reoriented by selective recrystallisation (Schmid and Casey, 1986)

EGRIP

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Crossed girdle in quartz

Type I

Type II

Law et al. (1986), modified

Lower Hemisphere

N = 766

234 m

Lower Hemisphere

N = 631

240 m

Lower Hemisphere

N = 716

250 m

Lower Hemisphere

N = 1371

272 m