Optical and igneous

Question 0

When light gets bent

Answer 0

Velocity changes
Rays get bent
2 new vibration directions
New colour

Question 1

Pleochroism

Answer 1

Some anisotropic minerals strongly absorb light vibrating in one direction and transmit light vibrating in another

Question 2

Extinction

Answer 2

When one of the vibration directions becomes parallel with the lower polarizer no light gets through the upper polarizer

Question 3

Retardation

Answer 3

Amount by which the waves are out of phase

Question 4

F= v/weird a thing

Answer 4

Frequency remains unchanged
If light speed changes weird a thing does
Weird a thing is related to colour and so if it changes colour also does

Question 5

Uniaxial crystal structure

Answer 5

Hexagonal, trigonal, tetragonal

Question 6

Biaxial crystal structure

Answer 6

Orthorhombic, triclinc, monoclinic

Question 7

Retardation depends on

Answer 7

N of the two perpindicular vibration directions
Thickness of the crystal
Orientation of the crystal

Question 8

Retardation is equal to

Answer 8

Thickness times nhigh- nlow

Question 9

N is equal to

Answer 9

V air divided by v mineral

Question 10

O Ray

Answer 10

Ordinary Ray
W
Vibrates perpindicular to the plane containing the optic axis

Question 11

E Ray

Answer 11

Ray e

Vibrates in plane parallel to c axis

Question 12

Mineral identification

Answer 12

Colour 
Relief 
Pleochroism
Twinning: symmetric intergrowth of two or more crystals of the same mineral 
Cleavage: breaking of a mineral along crystallographically controlled planes 
Exosolution 
Alteration 
Zoning

Question 13

Heat sources in the earth

Answer 13

1. Heat from the early accretion and differentiation of the earth
2. Heat released by the breakdown of unstable radioactive nuclides

Question 14

Radiation

Answer 14

Transfer of Heat through particles/ waves through transparent material

Question 15

Conduction

Answer 15

Transfer of kinetic energy from hot to cold in opaque minerals

Question 16

Convection

Answer 16

Movement of ductile material due to density variations

Question 17

Advection

Answer 17

Transfer of Heat with rocks that are moving

Question 18

Classification criteria for igneous rocks

Answer 18

Colour: can be misleading
Texture: depends on cooling history so can be same
Minerals Present: depends on chemical comp
Chemical composition: most characteristic
Can vary
Need to be determined in lab

Question 19

How does the mantle melt

Answer 19

Increase temp
Decrease pressure
Add volatiles

Question 20

Partial melting

Answer 20

Separation of a partially melted liquid from the solid residue

Question 21

Under what realistic circumstances can melts be created

Answer 21

Hot spots
Plates seperate: decompression melting
Fluid fluxing

Question 22

Magmatic diversification

Answer 22

Partial melting

Magmatic differentation

Question 23

Magmatic differentiation

Answer 23

Magma mixing
Mixed processes
Assimilation/contamination

Question 24

Two essential processes of magmatic differentation

Answer 24

1. Creates a compositional difference between one or more phases in response to a change in a variable like pressure temperature of composition 2. Preserves a chemical difference by segregating a chemically distinct portion so that they may either form a rock or continue to evolve as seperate systems

Question 25

Effective ness of magmatic differentation depends on

Answer 25

Contrasts in physical properties such as density viscosity and diffusivity

Question 26

Equilibrium crystallization

Answer 26

Implies a mass balance; overall composition remains constant throughout crystallization

Question 27

Fractional crystallization

Answer 27

Implies that all crystallizing solids are removed or seperated from the magma as they form

Question 28

Assimilation

Answer 28

Wall rock must first be partially melted and the heat has to come from the magma itself

Question 29

Magma properties

Answer 29

Viscosity Temperature Composition Density

Question 30

Viscosity depends on

Answer 30

Density Volatile content Temperature

Question 31

Eruptive violence depends on

Answer 31

1. Amount of gas | 2. Ease with which gas escapes

Question 32

Chlorite zone

Answer 32

Chlorite, muscovite, quartz, albite | Greenschist facies

Question 33

Biotite zone

Answer 33

Biotite, muscovite, quartz, albite | Greenschist facies

Question 34

Garnet zone

Answer 34

Garnet, biotite, quartz, muscovite | Amphibolite facies

Question 35

Staurolite zone

Answer 35

Staurolite, garnet, biotite, quartz | Amphibolite facies

Question 36

Kyanite zone

Answer 36

Kyanite, garnet, biotite, quartz | Amphibolite facies

Question 37

Silimanite zone

Answer 37

Sillimanite, quartz, garnet, biotite | Amphibolite- granulite facies