Structures & textures 1

Today Updates: Evaluation today at end of class Lecture outline: Deformation and textures Timing of crystal growth and deformation

Metamorphic Textures Textures are small-scale penetrative features Relict Textures Inherited from original rock Blastoporphyritic (<-> porphyroblastic) Any degree of preservation Pseudomorphs of minerals or pre-metamorphic textures/structures New Textures (following)

New Textures

Pressure solution

Deformation within a crystal

Point defect

Line defect: edge dislocation virtual2002.tau.ac.il/users/www/68379/PDF_Papers/2_Micro_Macro/Dislocations.pdf

Slip virtual2002.tau.ac.il/users/www/68379/PDF_Papers/2_Micro_Macro/Dislocations.pdf http://info.lu.farmingdale.edu/depts/met/met205/plasticdeformation.html

www.msm.cam.ac.uk/phase-trans/abstracts/L9.pdf Deformation twins

Recovery Crystals recover from strain by: Migration of Vacancies Dislocations Annihilation (opposite sense dislocations) Polygonization- general term for formation of low-strain subgrains: dislocations gather

Defect migration

Extinctions and subgrains

Recrystallization Simple way to reduce lattice strain Grain boundary migration Subgrain rotation Solid-state diffusion creep at higher T Grain boundary sliding and area reduction Coalescence- recovery and recrystallization by which large grains form by the addition of smaller strained grains by grain boundary migration

Grain boundary migration and sub-grain rotation

Coalescence in quartzite

Examples of pre, syn, post-kinematic crystals

Syn-kinematic crystals Microboudinage: Growing zones try to keep up with stretching and breaking Spiral Porphyroblast: in shear zone shear results in crystal rotation: foliation captured, crystal rotates a bit, grows/captures

Syn-kinematic garnet