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PETROLOGY > Classification Of Igneous Rocks > Flashcards

Classification Of Igneous Rocks Flashcards

1
Q

molten rock material generated by partial melting of Earth ’ s mantle and crust

A

Magma

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2
Q

At temperatures over ____ above the crystallization temperature of most minerals, magma tends to be enriched in liquids and dissolved gases.

A

1200 ° C

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3
Q

Gas solubility in liquids is related to pressure. At high pressures in the lower crust and mantle, gases are readily dissolved in liquid magma. As magma rises towards Earth ’ s surface, decompression causes gases to segregate from the melt as a separate phase.

A

exsolution

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4
Q

Magma that solidifies within Earth produces _ or_ rocks.

A

intrusive or plutonic

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5
Q

are magma chambers of various sizes, shapes and depths that store magma within Earth

A

Plutons

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6
Q

Magma that rises and erupts onto the surface of Earth is called

A

Lava

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7
Q

rocks form by solidifi cation of lava and volcanic debris on Earth ’ s surface, producing rocks with small crystals and/or non - crystalline particles of various sizes.

A

Volcanic or extrusive

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8
Q

How d o w e c lassify i gneous r ocks?

A

Igneous rocks are classifi ed according to composition and texture.

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9
Q

enriched in the elements silicon and oxygen which bond together to form the silica tetrahedron.

A

silicate magmas

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10
Q

Silicate magmas contain anywhere from? (%)

A

40% to over 75%

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11
Q

magma and igneous rocks are classified as _, _, _, _based upon percent SiO 2

A

ultrabasic , basic , intermediate and acidic

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12
Q

Acidic rocks are also referred to as _ , based on their high SiO 2 content.

A

silicic

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13
Q

Dark - colored minerals are generally enriched in the elements _, _and are referred to as _, _

A

iron and magnesium, ferromagnesian or mafic minerals

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14
Q

Light colored felsic minerals are depleted in ferromagnesian elements and are generally enriched in elements such as_, _, _, _

A

silicon, oxygen, potassium and sodium.

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15
Q

is a very dark - colored (ultramaf i c) rock, depleted in SiO 2 (ultrabasic) and commonly enriched in the minerals pyroxene, olivine, amphibole and plagioclase. Ultramafi c plutonic rocks occur in Earth ’ s mantle

A

Peridotite

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16
Q

_, _are dark - colored (mafi c), SiO 2 - poor (basic) rocks rich in plagioclase, pyroxene and olivine. Basalt is a very common volcanic rock – encompassing the upper few kilometers of ocean

A

Basalt and gabbro

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17
Q

Classification of ig rock: Dark or greenish rocks rich in olivine; may also contain pyroxene or amphibole

A

Ultramafic

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18
Q

Dark - colored rocks containing pyroxene, amphibole ± olivine ± biotite

A

Mafic

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19
Q

Classification of ig rock Grayish to salt and pepper colored rocks rich in plagioclase, amphibole ± biotite ± quartz

A

Intermediate

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20
Q

Light - colored or red rocks rich in potassium feldspar, quartz ± biotite or muscovite

A

Felsic

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21
Q

Ultramafi rocks_, _(coarse and fine equivalent)

A

PERIDOTITE, Komatiite

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22
Q

Mafic _, _ (coarse and fine grained equivalent)

A

Gabbro Basalt

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23
Q

Intermediate _, _(coarse and fine grained equivalent)

A

Diorite Dacite

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24
Q

Felsic _, _
_, _
(coarse and fine grained equivalent)

A

Granodiorite Dacite

Granite Rhyolite

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25
Q

Light-colored, lightweight rock rich in gas holes (vesicles)

A

Pumice

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26
Q

Dark-colored, lightweight rock rich in gas holes (vesicles)

A

Scoria

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27
Q

Rock composed of fine-grained ash- to sand-sized volcanic rock fragments

A

Volcanic tuff

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28
Q

Rock composed of coarse-grained gravel and larger sized volcanic rock fragments

A

Volcanic breccia

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29
Q

are gray - colored (intermediate) to salt and pepper - colored rocks rich in hornblende, pyroxene and plagioclase. _, _contain more than half to almost two - thirds SiO 2 . _, _is a common volcanic rock around the Pacifi c Ring of Fire. _ volcanoes overlie diorite plutons.

A

Andesite and diorite

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30
Q

_, & are light - colored (felsic) rocks, containing approximately two - thirds SiO 2 , rich in plagioclase, alkali feldspar and quartz and also containing small amounts of hornblende and biotite. _ is a volcanic rock that, like andesite, occurs around the Pacifi c rim. _ is a plutonic rock that underlies andesite – dacite volcanoes.

A

Dacite and granodiorite

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31
Q

_, _ are light - colored (felsic) rocks containing more than two thirds SiO 2 (silicic or acidic) and rich in quartz, alkali feldspar with small percentages of plagioclase and biotite. _ is a volcanic rock that usually erupts in thick, continental crust. _ plutons also occur in continental crust.

A

Rhyolite and granite

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32
Q

_ those characterized by the absence of crystals, include frothy, vesicular rocks such as pumice (light colored) and scoria (dark colored). Other non - crystalline rocks include those with glassy textures such as obsidian or those enriched in rock fragments. Fragmental, also known as _, volcanic rocks include tuff (volcanic ash to gravel size) and breccia (larger than gravel size).

A

Non crystalline, pyroclastic

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33
Q

The degree of crystallization can be classifi ed into _, _, _

A

holocrystalline , hypocrystalline and holohyaline

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34
Q

_ minerals contain complete crystal faces that are not impinged upon by other crystals

A

Euhedral

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35
Q

_ crystal faces contain partially complete crystal forms in which at least one of the crystal faces is impinged upon by adjacent rock material

A

Subhedral

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36
Q

In subhedral textures, crystal growth may be aborted due to:

A

Contact against previously formed minerals.
• Nucleation on pre - existing surfaces such as early formed crystals or the margins of the magma chamber.
• Resorption in which pre - existing euhedral crystals are partially remelted.
• Other secondary alteration processes that destroy pre - existing euhedral faces.

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37
Q

_ crystals lack any observable crystal faces.

A

Anhedral

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38
Q

remaining voids between existing crystal forms are referred to as _

A

interstitial space.

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39
Q

Textures: plutonic rocks include _, _, _

A

coarse - grained pegmatitic, phaneritic, phaneritic – porphyritic textures.

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40
Q

Textures: fine grained _, _

A

fine - grained aphanitic or aphanitic – porphyritic crystalline textures.

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41
Q

texture is characterized by large crystals averaging more than 30 mm in diameter.

A

Pegmatitic

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42
Q

Pegmatitic textures develop most commonly in?

A

granitic plutons with high volatile contents.

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43
Q

Phaneritic texture implies crystal diameters ranging from

A

1 to 30 mm.

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44
Q

Phaneritic textures may be subdivided into fine (_ in diameter), medium ( _mm) or coarse ( _mm) grained. Fine - grained phaneritic textures commonly develop in shallow plutonic structures such as _, _

A

1-3mm

3 – 10

10 – 30

dikes and sills.

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45
Q

textures contain small crystals less than 1 mm in diameter that are not generally discernible to the eye.

A

Aphanitic

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46
Q

textures contain microlite crystals large enough to be identifi ed with a petrographic microscope

A

Microcrystalline

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47
Q

> 50% of the rock this is a_ . If phenocrysts encompass < 50% of the rock volume, the term _

A

granite porphyry

porphyritic granite

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48
Q

Rocks with _ textures consist of two distinctly different size crystals

A

porphyritic

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49
Q

Large crystals are referred to as _ ; finer grained material constitutes the _ .

A

phenocrysts

groundmass

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50
Q

In _ textures, all crystals are visible to the eye, but the phenocrysts are distinctly larger than the groundmass crystals

A

porphyritic – phaneritic

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51
Q

In rocks with _ textures, the larger phenocrysts are embedded in an aphanitic groundmass composed largely of microcrystalline, cryptocrystalline or glassy material

A

porphyritic – aphanitic

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52
Q

The _ represents the initial crystallization temperature below which crystals and liquids coexist

A

liquidus line

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53
Q

Below the liquidus temperature, crystals nucleate and continue to grow at _

A

subliquidus temperatures.

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54
Q

The _ separates a higher temperature f i eld containing liquids and solid crystals from a lower temperature fi eld in which only solid crystalline material exists

A

solidus line

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55
Q

Temperatures below the solidus line are referred to as _.

A

subsolidus temperatures

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56
Q

involves the formation of new crystals, called nuclei or “ seed ” crystals, large enough to persist and grow into larger crystals.

A

Crystal nucleation

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57
Q

The crystal nucleation rate , the number of new seed crystals that develop per volume per time unit, is commonly expressed as

A

nuclei/cm 3 /s

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58
Q

occurs when liquids are cooled to temperatures below the liquidus line.

A

Undercooling

59
Q

represents undercooling of the magma.

A

Subliquidus crystal nucleation

60
Q

a measure of the increase in crystal radius over time.

A

crystal growth rate

61
Q

, the rate at which elements migrate through magma, depends primarily on the viscosity of the melt.

A

Diffusion

62
Q

are elements that tend to increase molecular linkage, thereby increasing viscosity.

A

Network formers

63
Q

Network formers in silicate melts include _, _, _

A

silicon, oxygen and aluminum.

64
Q

are elements that decrease molecular linkage. I. E Mg and Fe

A

Network modifiers

65
Q

occurs when melts of any composition come into contact with liquid water or air

A

Quenching

66
Q

_contain recognizable phenocrysts in a glassy groundmass and are said to have a _ .

A

Vitrophyres, vitrophyric texture

67
Q

Growth commonly occurs outward from existing crystal nuclei to produce rounded masses of radiating crystals called _

A

spherulites

68
Q

,glassy SiO 2 - rich volcanic rocks with higher water contents than obsidian

A

Perlites

69
Q

characterized by a cloudy appearance and curved or subspherical cooling cracks called perlitic crack

A

perlitic texture

70
Q

is encountered when bubbles constitute 70 – 80% of the magma volume

A

fragmentation surface

71
Q

defi ned as containing > 30% vesicles by volume, include pumice and scoria

A

Vesicular rocks

72
Q

Rocks that contain smaller amounts (-%) of vesicles are named using a modifi er such as vesicular basalt or vesicular andesite

A

5 – 30%

73
Q

rocks with just a few vesicles ( _%) are given names such as vesicle - bearing basalt and andesite.

A

< 5

74
Q

Volcanic eruptions eject broken rock particles of varying sizes, known as _ (which means fi ery fragment)

A

pyroclasts

75
Q

Pyroclasts may be ejected into the atmosphere as airborne _ or transported along Earth ’ s surface as pyroclastic fl ows.

A

tephra

76
Q

Pyroclasts consist of several different types of materials:
_: pyroclasts contain fragments such as basalt, andesite or other rocks.
_:composed of glassy fragments, most commonly pumice or scoria shard
_:pyroclasts contain minerals.

A

Lithic
Vitric
Crystal

77
Q

Ash consists of sand - sized and fi ner sized pyroclasts ( _ mm diameter) which can be subdivided into coarse ash (_ mm) and fi ne ash ( _ mm) or dust

A

< 2

0.0625 – 2
< 0.0625

78
Q

display random shard orientations and spherical to ellipsoidal pumice vesicles

A

Unwelded tuffs

79
Q

_ results as fragments become progressively fused together as porosity decreases during compaction.

A

Welding

80
Q

have concentrations greater than 1 wt % in Earth ’ s crust.

A

Major elements

81
Q

_and _ are the third and fourth most abundant elements by weight in Earth ’ s crust.

A

Aluminum, iron

82
Q

minor oxide compounds such as _, _, _

A

titanium oxide, manganese oxide and phosphate.

83
Q

rhyolite contains _ SiO 2
dacite _% SiO 2
andesite _% SiO 2
basalt _% SiO 2 .

A

> 66%
63 – 66%
52 – 63
45 – 52

84
Q

Note the chemical trends depicted: as SiO 2 concentration _, FeO, MgO, CaO and TiO 2 _ while Na 2 O and K 2 O _.

A

increases, decrease, increase

85
Q

_ consist of those elements that commonly occur in concentrations of 0.1 1.0%

A

Minor elements

86
Q

(4)are among the most common minor elements

A

Chromium, manganese, phosphorous, hydrogen and titanium

87
Q

Igneous rocks with SiO 2 concentrations in excess of 66% tend to be enriched in minor elements such as (3)

A

Li, Be and Ba.

88
Q

occur in crustal rock in concentrations of < 0.1% by weight and are typically measured in parts per million ( < 1000 ppm).

A

Trace elements

89
Q

is a measure of the ease with which an element fi ts into a crystal structure, and is analogous to the description of a compatible or incompatible person

A

Compatibility

90
Q

Compatible elements tend to form long - lasting bonds and incorporate into crystal structures. Compatible elements are immobile in that they do not readily migrate from the crystal structure. True or false

A

T

91
Q

The restite is enriched in compatible elements and depleted in incompatible elements. Conversely, magmas derived from partial melting are enriched in incompatible elements and depleted in compatible elements. T or f

A

T

92
Q

With small degrees of partial melting, incompatible elements such as (4)are depleted in the restite and enriched in magmas that migrate upward towards Earth ’ s surface.

A

K, Rb, Sr and Ba

93
Q

The restite rock, from which the partial melts have been removed, tends to be enriched in compatible elements such as (9)and depleted in incompatible elements

A

Fe, Mn, Zn, Ti, V, Cr, Co, Ni and Cu,

94
Q

Trace elements include rare (3)

A

Earth elements, high fi eld strength elements and large ion lithophile

95
Q

This process standardizes the differences between even and odd atomic numbered REE concentrations and makes data presentation graphs easier to plot and comprehend. The net result typically produces a relatively fl at REE concentration pattern. This process is referred to as a _ (Hess, 1989 )

A

chondrite - normalized pattern

96
Q

Light rare Earth elements (LREE) such as lanthanum (La), cesium (Ce), praseodymium (Pr), neodymium (Nd) and samarium (Sm) are situated on the _ end of the periodic table

A

Left

97
Q

all REE are incompatible. T or f

A

T

98
Q

LREE elements are more incompatible than HREE. T or f

A

T

99
Q

elements are characterized as having a relatively high ionic charge (+3 or +4) for a given radius

A

High fi eld strength (HFS)

100
Q

Ti, Ni, Cr, V, Zr, Hf, Nb, Ta and Y

A

HFS

101
Q

_ , situated at the right end of the periodic table, include europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu).

A

Heavy rare Earth elements (HREE)

102
Q

Trace elements containing an ionic radius : valence charge ratio of greater than 0.2 are referred to as

A

large ion lithophile (LIL) elements

103
Q

elements include Cs, Ba, Rb, Sr, U, Pb, K, Zr, Th and Ta

A

LIL

104
Q

_ elements tend to be mobile in partial melts and depleted in the restite

A

LIL

105
Q

useful in determining the role of hydrous fl uid interaction and the parental source of the partial melt

A

LIL

106
Q

lithospheric magma source is indicated if an igneous rock is _ in Sr and Nd (LREE)
Enriched or depleted?

A

enriched

107
Q

asthenospheric magma source is suggested if Sr and Nd are _ in an igneous rock.
Enriched or depleted?

A

depleted

108
Q

Rb, Ba and Th are among the (less, moderate, most) incompatible elements

A

Most

109
Q

Sm and Hf are)(most, moderately, less) incompatible.

A

Moderately

110
Q

Sr is more compatible than Rb; Sm is more compatible than Nd and Lu is more compatible than Hf. T of f

A

T

111
Q

Eu is incompatible, except in the presence of _?

A

plagioclase

112
Q

occur in concentrations of less than ∼ 5%

A

Accessory minerals

113
Q

The _, also called the _, is the proportion of mafi c minerals in the total population of felsic and mafi c minerals given as:

A

color index (CI), mafi c index

114
Q

< 40% DCM: _

A

Felsic

115
Q

40 – 70% DCM:

A

intermediate

116
Q

70 – 90% DCM:

A

Mafic

117
Q

> 90% DCM:

A

ultramafi c

118
Q

IUGS color index rock modifier terms

< 35% DCM:

A

leucocratic

119
Q

IUGS color index rock modifi er terms

35 – 65% DCM:

A

mesocratic

120
Q

IUGS color index rock modifi er terms

> 65% DCM:

A

melanocratic

121
Q

Accurate point count analysis requires moving a thin section incrementally on a grid system such that at least mineral points are tabulated for each thin section.

A

400

122
Q

The fi rst norm classifi cation

A

CIPW norm

123
Q

Quartz ± feldspars and/or magnesium orthopyroxene

A

SiO 2 oversaturated

124
Q

Feldspars and/or magnesium orthopyroxene only

A

Saturated sio2

125
Q

Forsterite olivine, nepheline, leucite and other feldspathoids ± feldspars and/or orthopyroxene minerals. Excludes quartz

A

Sio2 undersaturated

126
Q

(2) – indicators of SiO 2 undersaturation

A

magnesium olivine or feldspathoids

127
Q

Al 2 O 3 > CaO + Na 2 O + K 2 O

A

Peraluminous

128
Q

Muscovite, corundum, topaz, garnet, tourmaline, cordierite, andalusite, biotite

A

Peraluminous

129
Q

Hornblende, epidote, melilite, biotite, pyroxene

Al abundance?

A

Metaluminous

130
Q

Na 2 O + K 2 O < Al 2 O 3 < CaO + Na 2 O + K 2 O

A

Metaluminous

131
Q

Al 2 O 3 = Na 2 O + K 2 O

A

Subaluminous

132
Q

Olivine, orthopyroxene, clinopyroxene

A

Subaluminous

133
Q

Al 2 O 3 < Na 2 O + K 2 O

A

Peralkaline

134
Q

Aegerine, riebeckite, arfvedsonite, aenigmatite, astrophyllite, columbite, pyrochlore

A

Peralkaline

135
Q

Altered plag

A

Scapolite

136
Q

Q in qapf

A

Quartz, tridymite, cristobalite

137
Q

A in qapf includes 5 moles of anorthite. T or f

A

T

138
Q

Feldspathoids include the minerals nepheline, sodalite, cancrinite, leucite, analcite, nosean, hauyne and kalsilite. T or f

A

T

139
Q

> 40% olivine rock

A

Peridotite

140
Q

<40% olivine

A

Pyroxenite

141
Q

applies for igneous rocks with > 10% felsic minerals and < 90% mafi c mineral (M) content by volume

A

QAPF modal classification

142
Q

used for ultramafi c plutonic rocks containing > 90% dark - colored minerals

A

Modal classifi cation of ultramafi c plutonic rocks

143
Q

classifications are suitable for use with extremely fine grained or glassy volcanic rocks that are relatively unaltered and contain less than 2% H20 and 0.5% CO2

A

total alkali to silica (TAS)

PETROLOGY (1 decks)

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