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Microstructure evolutionMicrostructure evolution

during creep andduring creep andannealing of mineralsannealing of mineralsand rocksand rocks

Microstructure evolutionMicrostructure evolution

during creep andduring creep andannealing of mineralsannealing of mineralsand rocksand rocks

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D. Tatham,D.J. Prior, E. Mariani, S.J. Covey-Crump, J. Mecklenburgh, J. Wheeler

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High temperature deformation in the EarthHigh temperature deformation in the EarthHigh temperature deformation in the EarthHigh temperature deformation in the Earth

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Ed Garnero 

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How do we gain insight into mechanisms of

deformation in the Earth’s crust and their implications?

SE NWTorre Saliere

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Fold structure in theFold structure in the MorcleMorcle NappeNappe,, SalanfeSalanfe, Swiss, SwissAlpsAlpsFold structure in theFold structure in the MorcleMorcle NappeNappe,, SalanfeSalanfe, Swiss, SwissAlpsAlps

1 Km

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Naturally deformed systems

 

Electronbackscatter

diffraction(EBSD)

Tools for understanding high temperatureTools for understanding high temperaturedeformation of rocksdeformation of rocks

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“Final microstrucutres ”

Experimental

rockdeformation

“Post mortem 

analysis ”

Modelling

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These may tell us about:

•  

We track microstructural evolutionthrough in-situ heating and deformationexperiments in the SEM with

simultaneous EBSD

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• the behaviour of special (twin, CSL) boundaries

• the control of orientation/chemistry on boundary migration

• what mechanisms control static and dynamic recrystallization

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The SEM in LiverpoolThe SEM in LiverpoolThe SEM in LiverpoolThe SEM in Liverpool

• The CamScan X500CrystalProbe is specificallydesigned for high-temperature in situ experiments.

• Tilted column permitsexperimentation on horizontal

6

.

• Sample assembly anddetectors separated bywater-cooled heat shield,reducing contamination ofsignal at high experimentaltemperatures.

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Static Heating StageStatic Heating StageStatic Heating StageStatic Heating Stage

• Coiled Ta wire resistanceheater.

• Capable of furnace

temperatures in excess of1200oC.

• Equates to sample surfacetemperatures in excess of

o

7

.

• Samples up to 9x9x3mm sit ina cavity in graphite furnacecore.

• Furnace heating path controlled

by a Oxford InstrumentsIntelligent TemperatureController.

Seward et al., 2000 Scanning , 24, 232-240.

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Annealing of deformed NaClAnnealing of deformed NaClAnnealing of deformed NaClAnnealing of deformed NaCl

8Bestmann et al., 2005. J. Struct. Geol. 47, 447-457 Piazolo et al. 2006, Tectonophysics 427, 55-71

Slide8.avi 

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Before heating

Annealing of deformed NaClAnnealing of deformed NaCl

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500 µµµµmBestmann et al., 2005. J. Struct. Geol. 47, 447-457 

Piazolo et al. 2006, Tectonophysics 427, 55-71

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after 4.5h heating at 350-410°°°°C

Annealing of deformed NaClAnnealing of deformed NaCl

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500 µµµµm

Bestmann et al., 2005. J. Struct. Geol. 47, 447-457 

Piazolo et al. 2006, Tectonophysics 427, 55-71

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GBM at low T GBM at high T

12 Piazolo et al., 2006, Tectonophysics 427, 55-71

Increasing length of straight segment movement

Increasing face control

Decreasing influence of pre-existing substructure

Decreasing tendency to create ‘poikiloblasts’

Increasing continuity (time and space) of movement

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Grain growth in annealed copper at 850Grain growth in annealed copper at 850ooCCGrain growth in annealed copper at 850Grain growth in annealed copper at 850ooCC

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Video is 30x real-time

Slide13.avi 

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Grain growth in annealed copper at 850Grain growth in annealed copper at 850ooCCGrain growth in annealed copper at 850Grain growth in annealed copper at 850ooCC

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In In- -situ situ deformation & heating stagedeformation & heating stageIn In- -situ situ deformation & heating stagedeformation & heating stage

• Stepper motor-driven tensileheating/deformation rig in-situ in SEM.

• Opposing lead screws allowtensile load & strain whilekeeping the area of investigationunder the electron beam.

 

LVDTs

Load

cell

Steppermotor

Sample

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•  

capable of furnacetemperatures in excess of1400oC & sample surfacetemperatures well in excess of1000oC.

• Samples thermally isolated fromdeformation assembly byceramic jig.

• Controlled via LabVIEW.

Water-cooled plate

HeatersCeramic sample jig

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Deformation in copper at ~700Deformation in copper at ~700ooCCDeformation in copper at ~700Deformation in copper at ~700ooCC

16Video is 300x real-time, 0.8mm total extension

Slide16.avi 

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P,T

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Pressure

• inhibits brittle failure

• promotes GBM

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In the SEM we need higher temperature but...

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Practicalities of working on geologically important materialsPracticalities of working on geologically important materials

20Mariani and Tatham, unpublished experiments; Bestmann. unpublished experiments 

Slide20.avi 

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LVDT

fixed piston

displacement rods

Tracking microstructure evolutionTracking microstructure evolution

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High T creep rig 

(to Mariani, July 09) 

New SEM stage 

(to Prior, January 09) passive load

moving piston

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microstructural evolution

Tracking microstructure evolutionTracking microstructure evolution

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shear strain      s       t      r      e

      s      s

rheology 

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U n d e f o r m e d

Tracking microstructure evolutionTracking microstructure evolution

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5 0 0 1 0 0 0

s c a l e / m s c a l e / m

00 5 0 0 1 0 0 0

shear strain = 0.5

 T=973K 

P = 3 0 0 M P a

With Julian Mecklenburgh,

Manchester 

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Higher ResolutionHigher ResolutionHigher ResolutionHigher Resolution

Carrara marble

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Solenhofen limestone

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Thank you

 

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pcwww.liverpool.ac.uk/~tatham/mtmovies.zip