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GEOS 3464 EARTH MATS > EXAM 2 MATERIAL > Flashcards

EXAM 2 MATERIAL Flashcards

1
Q

when did petrography begin and who invented it?

A
  • 1828
  • william Nichol
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2
Q

How was petrography invented/developed?

A

Polarized light was produced from by cutting Iceland spar, a variety of calcite, into a prism.

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3
Q

what is the idea thickness of a thin section?

A

30 microns

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4
Q

what technique did henry Sorby develop?

A

-cutting rocks into thin slices, affixing them to a microscope so light could be transmitted through the crystal

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5
Q

what is a minerals’ refractive index?

A

how much the velocity of light slows when it passes through a crystal

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6
Q

how is refractive index calculated?

A

(the velocity of light in air)/(the velocity of light in the mineral)

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7
Q

how are refractive indices measured?

A

a device known as a refractometer

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8
Q

what is the angle of refraction?

A

the angle made by a refracted ray of light

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9
Q

define Snell’s law

A

sini/sinr=RI2/RI1

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10
Q

what is the angle of incidence

A

describes the angle light impinges on the boundary

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11
Q

what range of the electromagnetic spectrum is visible to the human eye?

A

400-700 microns

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12
Q

what is the velocity of light in a vacuum?

A

300,000 Km/s

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13
Q

is the speed of light the same in all materials?

A

NO, it slows thus resulting in the light ray bending (refraction)

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14
Q

what is retardation of light in minerals?

A

a function of the thickness of the mineral

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15
Q

what is the range and color of first-order interference colors?

A

red at 550 is first order interference color
0-550 nm

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16
Q

what is the range and color of second-order interference colors?

A

blue is second order interference color
550-1100 nm

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17
Q

what is the color of third-order interference colors?

A

pink

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18
Q

what is the nm range associated with each order color?

A

550 nm

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19
Q

Do isometric crystals exhibit interference colors, why or why not?

A

NO, crystals have three axes of equal length

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20
Q

what are isotropic materials?

A

have only one refractive index and are independent of the path of light

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21
Q

what is birefringence

A

the difference between the minimum and maximum index of refraction

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22
Q

why do interference colors exist

A

as the N-S fast and slow vibrating waves pass through the upper polarizer, they are out of phase, causing interference and their resulting colors.

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23
Q

what is extinction in minerals?

A

light is completely eliminated by the upper polarizer, appearing dark.

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24
Q

GO BACK TO ANISOTROPIC/ISOTROPIC SECTION (CH. 6)

A
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25
Q

are extinction angles important in mineral ID?

A

YES

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26
Q

what are fast and slow vibration directions related to?

A

promoninent crystallographic characteristics: cleavage, twinning

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27
Q

how can fast and slow vibration directions be measured?

A

with the use of an accessory plate

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28
Q

how is pleochroism observed?

A

in polarized light, the color of a mineral changes depending on the orientation of the crystal

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29
Q

what causes pleochroism?

A

the absorption of different wavelengths of light in different directions

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30
Q

is pleochroism a useful diagnostic property?

A

YES

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31
Q

what is the difference between a uniaxial and biaxial optical indicatrix

A

uniaxial has one optic axis biaxial two optic axes

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32
Q

which crystal classes have biaxial optical indicatrix and how many RI do they have?

A
  • orthorhombic
  • monoclinic
    -triclinic

THREE RI

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33
Q

what are there two types of optical indicatrix?

A
  • uniaxial
  • biaxial
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34
Q

which crystal classes have uniaxial optical indicatrix and how many RI do they have?

A
  • tetragonal
  • hexagonal

TWO RI

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35
Q

what is the optic angle designated as?

A

2v

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36
Q

what is the optic angle measuring?

A

the acute angle between two axes

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37
Q

What is modal analysis

A

the areal abundance of a mineral

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38
Q

what techniques are involved in modal analysis?

A

comparing what is observed in thin section to a chart showing typical abundances

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39
Q

TERNARY diagram- CH7 slide 10
know how to solve and know how to normalize and plot lines on diagram

A
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40
Q

what percentage abundance must a mineral be to be considered major elements

A

more than 1 wt.%

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41
Q

what percentage abundance must a mineral be to be considered minor elements

A

1.0-0.1 wt%

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42
Q

what percentage abundance must a mineral be to be considered trace elements?

A

less than 0.1 wt%

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43
Q

what is the importance of silicon and oxygen in rock forming minerals?

A

the crust is made almost entirely of oxygen and silicates

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44
Q

BINARY DIAGRAMS- CH7 (slide 7)

calculation of mineral formulas

A
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45
Q

what is the difference and similarities between fayalite and forsterite as far as composition?

A
  • both end members of olivine
  • Fe rich= Fayalite
  • Mg rich= forsterite
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46
Q

be familiar with the calculation steps in determining mineral formulas

A
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47
Q

ch 7 slide 8

A
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48
Q

what are tie lines and what do they represent?

A

horizontal lines connection two coexisting phases

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49
Q

how can igneous minerals be structured in a 3d manner

A

tectosilicates

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50
Q

what is the only SiO2 mineral that does not contain tectosilicates?

A

stishovite

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51
Q

what group has single chain silicates?

A

the pyroxene group

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52
Q

what group has double chain silicates?

A

the amphibole group

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53
Q

what are both chain structures known as?

A

inosilicates

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54
Q

what are sheet silicates known as?

A

phyllosilicates

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55
Q

what are double tetrahedra silicates known as?

A

sorosilicates

56
Q

what are the different types of silicate structures?

A
  • infinite networks
  • infinite sheet
  • single chain
  • double chain
  • double tetrahedron
  • Independent tetrahedra
57
Q

what are independent tetrahedra silicates known as?

A

nesosilicates OR orthosilicates

58
Q

what are ring structures known as?

A

cyclosilicates

59
Q

what are the three polymorphs of k feldspar

A

Microcline, orthoclase, sanidine

60
Q

how are the three polymorphs of kfeldspar DIFFERENT from each other?

A

in microcline: Al position is ordered
in orthoclase: Al position is partial ordered
in sanidine: Al position is totally disordered

61
Q

can quartz and nepheline coexist stably in the same rock why/why not?

A

NO

nepheline in undersaturated in silicon, but quartz is silicon rich

62
Q

rocks with modal quartz are considered______________?

A

silica oversaturated

63
Q

rocks with modal nepheline are considered______________?

A

silica undersaturated

64
Q

what makes feldspathoids unusual?

A

similar to feldspars in structure and appearance. but contain much less silica.

65
Q

what is the major difference between orthopyroxene and clinopyroxene?

A
  • orthopyroxenes are orthorhombic
    HIGH Ca
  • clinopyroxenes are monoclinic
    LOW Ca
66
Q

invarient pointss, univariant lines GO BACK AND REVIEW

A
67
Q

in order for equilibrium to exist, what gradients must be eliminated?

A
  • system
  • temperature
  • pressure
  • chemical
68
Q

what is Gibbs phase rule equation?

A

f=c+2-Φ

69
Q

what are phases and how are the denoted in the Gibbs phase rule?

A

individual minerals, liquids and gases
denoted by the Greek letter Φ (phi)

70
Q

what are components and how are they denoted in the Gibbs phase rule?

A

the minimum number of constituents needed to describe the phases present
denoted by the letter c

71
Q

what are degrees of freedom and how is it denoted in the Gibbs phase rule?

A

how many variables can be changed without changing the phases present. denoted by the letter f

72
Q

what is the Maximum number of phases a rock can contain when there are 0 degrees of freedom (f)?

A

number of components present plus 2 (c+2)

73
Q

what is the Maximum number of phases a rock can contain when there is one degree of freedom (f)?

A

number of components plus 1
(c+1)

74
Q

what is the Maximum number of phases a rock can contain when there are two degrees of freedom (f)?

A

number of components is equal to the number of phases
(c=Φ)

75
Q

what happens to the freezing point of a solution if salt is added to water, is there a limit?

A

the freezing point is depressed.

YES

76
Q

what does a liquidus line represent in a salt-water phase diagram?

A

above the line is salty water, below the line, ice and salty water are in equilibrium

77
Q

does a salt-water phase diagram have a solidus line?

A

NO

78
Q

what does the eutectic represent in a phase diagram?

A

the lowest possible temperature at which a liquid can exist

79
Q

what is meant by the term liquidus?

A

all components are liquid

80
Q

what is meant by the term solidus?

A

all components are solid

81
Q

what is the effect of two minerals present together and how do they effect each other

A

the minerals dissolve into each other, lowering their melting point

82
Q

what is the lever rule and what does it allow us to do?

A

allows the determination of mineral wt percentages graphically

83
Q

what is a solvus line?

A

a line the separates a solid phase from a solid1 + solid 2 phase

84
Q

what is exsolution

A

the separation of one mineral from another

85
Q

how is exsolution observed in alkali feldspars?

A

perthite texture

86
Q

how does adding a third component to the eutectic fluid effect solution AB

A

it lowers the liquidus of AB

87
Q

what is the difference between binary and ternary eutectics?

A

binary eutectics contain two components
ternary eutectics contain three components

88
Q

Why does a ternary eutectic occur at lower temperature than the binary eutectics?

A

because it has more components=lower crystallization temperature

89
Q

how does the earth seek a state of equilibrium?

A

by eliminating gradients in intense variables

90
Q

what is transport law and its two required components?

A

laws governing transport rates
1- the driving force
2- the resistance term

91
Q

what is darcys law

A

describes fluid flow through a porous medium

92
Q

what is viscosity

A

the property of a fluid to resist flow when stress is applied

93
Q

what is fouriers law

A

describes the flow of heat by CONDUCTION ONLY

94
Q

what is fricks law

A

describes the diffusion of atoms

95
Q

what factors control viscosity

A

temperature

96
Q

when were the first absolute age estimation of earth materials produced AND by whom?

A

1907
Bertram Boltwood

97
Q

what did kelvin theorize about the age of the earth. why was it INCORRECT?

A

he said the earth could only be 100 Ma.

he theorized that the earth was losing its initial heat and could not generate its own. obviously not correct

98
Q

what are the four types of radioactive decay?

A
  • Alpha
  • Beta
  • Electron capture
  • fission
99
Q

what is alpha decay and what is an alpha particle?

A

neutron ejects and alpha particle
contains 2 protons and 2 neutrons

100
Q

what is beta decay?

A

a neutron changes into a proton by emitting an electron (beta particle)

101
Q

what is electron capture decay?

A

electrons are captured by a nucleus, combines with a proton to create a neutron

102
Q

what is fission decay?

A

splitting of the nucleus into to equal sized, nuclei

103
Q

how is absolute age calculated using decay formula?

A

age= # of half lives X decay constant

104
Q

calculate an age give a parent:daughter of 1:15 and a half life of 10 Ma

A

40 Ma

105
Q

what are half lives

A

the amount of time it takes for an amount of radioactive material to be halved

106
Q

what are decay constants

A

proportionality between size of radioactive atoms and the rate at which they decrease

107
Q

what is blocking temperature

A

the temperature at which ions are no longer able to go into or out of a crystal

108
Q

what does radiometric age tell us

A

estimate how long ago rocks were formed

109
Q

where do melting processes occur?

A

divergent margins
- M.O.R

110
Q

what drives volcanism?

A

the ability to melt mantle and magma to ascend to the surface

111
Q

what drives magma ascent?

A

magma is less dense than the rock it formed from, therefore it rises

112
Q

what are the types of intrusive bodies of magma?

A

dikes
sills

113
Q

what is underplating

A

the addition of material (usually from the mantle) underneath a tectonic plate

114
Q

what kind of rock does silica rich magma produce?

A

andesite

115
Q

where does most melting on earth occur?

A

decompression at M.O.R

116
Q

name three magma sources (could be a location or a process)

A

1- decompression at M.O.R
2- mantle wedge above subducting plates
3- heating associated with mantle hot spots

117
Q

how can different types of rocks form from a single parent magma?

A
  • magmas cooling slowly
  • assimilation
  • fractionation
118
Q

what are mantle xenoliths?

A

pieces of the mantle brought to the surface through magma movement. IMPORTANT.

119
Q

at what depths are aluminum bearing minerals stable in mantle

A

20-400 kilometers

120
Q

what is the role of volatile content on melting?

A
  • lowers melting temperature
  • high gas pressure causes more explosive eruptions
121
Q

what are the three ways melting can occur?

A
  • raising temperature
  • lowering pressure
  • adding water (lowers melting temperature)
122
Q

what is the difference between hydrous and anhydrous melting?

A

hydrous melts contain water molecules MORE COARSER GRAINED

anhydrous melts are finer grained

123
Q

what are the most abundant volcanic gases being emitted at the surface

A
  • water
  • CO2
124
Q

what is the importance of magma density/ density contrasts

A
  1. drives tectonic plates and magma movement.
  2. density contrast between crystals can change magma composition
125
Q

what controls magma density?

A

composition

126
Q

how is rock conductivity related to heat flow?

A

different rocks have different thermal conductivity

127
Q

can heat transfer be related to convective flow in magma bodies

A

yes, convection dramatically increases cooling rates

128
Q

what does settling velocity refer to?

A

how quickly crystals can settle in a melt

129
Q

what is stokes law used for?

A

used to calculate settling velocity

130
Q

what are the most important factors in settling velocity

A

crystal size and density

131
Q

what is laminar vs turbulent flow

A

laminar is low energy, turbulent is high energy

132
Q

what is fractionation

A

the separation of crystals from the liquid

133
Q

what are cumulates

A

rocks formed by the accumulation of crystals

134
Q

what is the origin of isotopic reservoirs, how do they evolve

A

originate via:
- planetary differentiation
- chemical reactions

evolve via:
- magmatic processes
- radiogenic isotope production

135
Q

what is modal layering

A

rocks showing layering of minerals

136
Q

what is assimilation by reaction

A

rock change the composition of magma by reacting with it, not melting

GEOS 3464 EARTH MATS (3 decks)

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