Deformation Mechanisms and Microstructures

Question 1

microscale deformation mechanisms that occurs within individual mineral grains

Answer 1

Intracrystalline deformation

Question 2

when the intracystalline deformation produces microstructure that affecting more than onebgrain such as grain boundary sliding or fracturing of mineral aggregates that is common in brittle deformation

Answer 2

Intercystalline deformation

Question 3

strain expression of mechanical bending or kinking of the crystal lattice particularly at very low temepratures Pagioclase and calcite

Answer 3

Deformation twins

Question 4

The process of forming deformation twins

Answer 4

mechanical twinning

Question 5

This mineral exhibit a kind of deformation twin that involves simple shear along the twin plain where the kinked and unkinked part are mirror of one another about this plane occuring at a shear stress just above critical threshold of 10MPa.

This means, that it can deform by twinning at any level in the crust, and by surface as long the critical threshold is reached.

Answer 5

Calcite

Question 6

True or False: The more defects in a crystal lattice wether deformed or not, the higher the stored energy.

Answer 6

True

Question 7

Movement of vacancies

Answer 7

Diffusion

Question 8

crystal deffects that represented by either vacancies or less i portsntly impurities in the form of extra atoms in the lattice but the interest to some, is the point defect reperesented by missing atoms

Answer 8

Point defect

Question 9

a mobile line defect that contributes to intracrystalline deformation by a mechanism called slip ( movement of dislcation font within a plane)

Answer 9

Line defects/dislocation

Question 10

is a mechanism involving migration of vacancies in crystallograpic in crystallograpic lattices

Answer 10

Diffusion or creep

Question 11

is a diffusion of vacancies through crystal wherein strain rate is taken into consideration, the higher smaller the grains, the higher the strain rate. keep in mind that the strain rate is not high, however at some point, when reach a grain boundary, the vacancies will then dissappear.

Answer 11

Nabarro - Herring Creep

Question 12

Because vacancies move toward sites of maximum stress, what does the final shape of the crystal acquire? during this process the crystal will gain regularity to become a regular crystal

Answer 12

fabric or strain

Question 13

True or False: Volume diffusion requires a lot energy so that the migration rate is highly temperature dependent: high temperature high vibration in the lattice, which increase rate

Answer 13

True

Question 14

is a migration of vacancies occurs at preferentially along grain boundaries. It is a bit less energy demanding than Nabarro-Herring Creep, and is more important in the formation of the plastic crust

Answer 14

Grain Boundary-Coble creep

Question 15

bears similarity to Coble Creep and geometrically and mathematically it can be treated in the same way.

Answer 15

Pressure solution or wet diffusion

Question 16

whats the difference between pressure solution and Coble creep?

Answer 16

diffusion occurs along a thin film of fluid along grain boundaries (solution seam)

Question 17

Wet diffusion is a microdeformation mechanism that results to volume reduction. This mechanism is what is known as,

Answer 17

chemical compaction

Question 18

a mobile line defect that contributes to intracystalline deformation by a mechanism called slip —– which, implies, movement of a dislocation front within a plane

Answer 18

dislocation

Question 19

Give the specific control for volume diffusion where vacancies move through crystals

Answer 19

temperature and stress

Question 20

controls for grain boundary; where vacancies move along grain boundaries

Answer 20

temperature and stress

Question 21

what are the controls for Pressure solution? where ions move in fluid films and pore fluid?

Answer 21

chemically and stress controlled

Question 22

is a type of dislocation that edge is an extra plane half plane of the crystal lattice

Answer 22

edge dislocation

Question 23

a dislocation line that is oriented parallele to the slip direction

Answer 23

screw dislocation

Question 24

the formation, motion and destruction of dislocations in a crystals

Answer 24

dislocation creep

Question 25

The process by which edge dislocations move

Answer 25

dislocation glide

Question 26

True or false: Dislocation creeps allows the deformation to take place at much lower differential stress that required for brittle fracturing

Answer 26

True

Question 27

True or false: Dislocation movements weaken or damage a mineral

Answer 27

false

Question 28

These are atomic-scale deformation structures such as dislocations can only be studied by means of electron microscopy at 10 000-100000x mg. They are reffered as microstructures and carry information about temperature, state of stress and rheological properties at the time of deformation

Answer 28

Microstructures