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Petrology > Optical and igneous > Flashcards

Optical and igneous Flashcards

0
Q

When light gets bent

A

Velocity changes
Rays get bent
2 new vibration directions
New colour

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1
Q

Pleochroism

A

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

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2
Q

Extinction

A

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

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3
Q

Retardation

A

Amount by which the waves are out of phase

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4
Q

F= v/weird a thing

A

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

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5
Q

Uniaxial crystal structure

A

Hexagonal, trigonal, tetragonal

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6
Q

Biaxial crystal structure

A

Orthorhombic, triclinc, monoclinic

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7
Q

Retardation depends on

A

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

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8
Q

Retardation is equal to

A

Thickness times nhigh- nlow

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9
Q

N is equal to

A

V air divided by v mineral

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10
Q

O Ray

A

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

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11
Q

E Ray

A

Ray e

Vibrates in plane parallel to c axis

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12
Q

Mineral identification

A 
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
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13
Q

Heat sources in the earth

A
  1. Heat from the early accretion and differentiation of the earth
  2. Heat released by the breakdown of unstable radioactive nuclides
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14
Q

Radiation

A

Transfer of Heat through particles/ waves through transparent material

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15
Q

Conduction

A

Transfer of kinetic energy from hot to cold in opaque minerals

16
Q

Convection

A

Movement of ductile material due to density variations

17
Q

Advection

A

Transfer of Heat with rocks that are moving

18
Q

Classification criteria for igneous rocks

A

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

19
Q

How does the mantle melt

A

Increase temp
Decrease pressure
Add volatiles

20
Q

Partial melting

A

Separation of a partially melted liquid from the solid residue

21
Q

Under what realistic circumstances can melts be created

A

Hot spots
Plates seperate: decompression melting
Fluid fluxing

22
Q

Magmatic diversification

A

Partial melting

Magmatic differentation

23
Q

Magmatic differentiation

A

Magma mixing
Mixed processes
Assimilation/contamination

24
Q

Two essential processes of magmatic differentation

A
  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
25
Q

Effective ness of magmatic differentation depends on

A

Contrasts in physical properties such as density viscosity and diffusivity

26
Q

Equilibrium crystallization

A

Implies a mass balance; overall composition remains constant throughout crystallization

27
Q

Fractional crystallization

A

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

28
Q

Assimilation

A

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

29
Q

Magma properties

A

Viscosity
Temperature
Composition
Density

30
Q

Viscosity depends on

A

Density
Volatile content
Temperature

31
Q

Eruptive violence depends on

A
  1. Amount of gas

2. Ease with which gas escapes

32
Q

Chlorite zone

A

Chlorite, muscovite, quartz, albite

Greenschist facies

33
Q

Biotite zone

A

Biotite, muscovite, quartz, albite

Greenschist facies

34
Q

Garnet zone

A

Garnet, biotite, quartz, muscovite

Amphibolite facies

35
Q

Staurolite zone

A

Staurolite, garnet, biotite, quartz

Amphibolite facies

36
Q

Kyanite zone

A

Kyanite, garnet, biotite, quartz

Amphibolite facies

37
Q

Silimanite zone

A

Sillimanite, quartz, garnet, biotite

Amphibolite- granulite facies

Petrology (2 decks)

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