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GLE 2024 (Day 2) > METAMORPHIC PETROLOGY (NON-FOLIATED METAMORPHIC ROCKS) > Flashcards

METAMORPHIC PETROLOGY (NON-FOLIATED METAMORPHIC ROCKS) Flashcards

1
Q

Composition of met rocks are determined by

A

Protolith chemistry

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2
Q

Refers to the size, shaper, orientation and intergranular relationships of the rock’s constituens

A

Texture

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3
Q

geometrical arrangement of grains

A

fabric

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4
Q

Texture inherited from protolith

A

Relict Texture

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5
Q

Inequant grains which one axis is significantly shorter that the other two axes and has a disc shaped pancake or paper-like shape

A

Tabular

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6
Q

Grains in which one is significantly longer than the other two which are not equal

A

Bladed

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7
Q

Grains in which one is significantly longer than the other two which are equal

A

Acicular

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8
Q

Cigar-shaped

A

Prolate

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9
Q

Grain size of aphanitic

A

<1mm

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10
Q

Phaneritic Gran size

A

> 1mm

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11
Q

Large relict grains from the protolith which has undergone deformation but still retains its orig composition.

A

Porphyroclasts

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12
Q

Common Porphyroclasts

A

Qtz and Felds

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13
Q

Oval-shaped feldspar porphyroclasts that resemble the shape of an eye and common in gneisses

A

Augen

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14
Q

Oval shaped quartz porphyroclasts

A

Flaser

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15
Q

Large grains that have experienced neocrystallization and growth in response to favorable T&P Conditions during metamorphism

A

Porphyroblasts

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16
Q

growth of new minerals stable at the temperature and pressure conditions of metamorphism

A

Neocrystallization

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17
Q

Common porphyroblasts

A

Garnet,
Staurolite,
Cordierite

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18
Q

occurs when no preferred orientation of inequant grains is visible

A

Random Grain Orientation

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19
Q

occurs when equant grains are oriented sub-parallel to one anther and can produce lineation and foliations

A

Peferred Grain Orientation

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20
Q

Linear like features similar to pencils all point to a common direction which is commonly formed by preferred orientation of acicular, bladed, or rod-like grains with sub-parallel long axes

A

Lineations

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21
Q

Minerals which are usually acicular, bladed or rod-like

A

Inosilicates

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22
Q

Metamorphic layers oriented parallel to one another like pages in a book formed from the Preferred Grain orientation of tabular grains with subparallel long axes

A

Foliations

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23
Q

Minerals which are usually tabular and produce foliations

A

Phyllosilicates

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24
Q

What kind of stress produce random grain orientation?

A

Uniform Stress

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25
Q

Lineations and foliations are produced by

A

Non uniform stresses

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26
Q

Rock category in which crystals lack a preferred orientation

A

Non Foliated

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27
Q

Rock category in which crystals possess a preferred orientation

A

Foliated

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28
Q

What kind of metamorphism usually produce non foliated rocks?

A

Contact or Burial

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29
Q

What happens in such metamorphism

A

Uniform lithostatic stress produces equant or randomly arranged minerals so that prominent foliated textures arent produced

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30
Q

a fine grained <1mm diamter non forliated fabric thatd evelops by contact metamorphism

A

Hornfelsic texture

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31
Q

Met rock with fine grained non foliate fabric usually derived from fine-grained protolith rocks such as shale, mudstones, tuff or basalt

A

Hornfels

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32
Q

Characteristics of Hornfels

A

1) mostly equant crystals
2) Random grain orientation
3) Can preserve relict sed fabrics such as beddings

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33
Q

Where do hornfels usually develop?

A

Metamorphic Aureoles adjacent to intrusions (Contact met)

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34
Q

Common minerals of Hornfels

A

Musc
Biot
Andal
Cord
Plag
kfelds
Epid
Amph
Pyx

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35
Q

Hornfels is __________ and ___________ than mudstone

A

Harder and more brittle

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36
Q

Characterized by large equant grains (>1mm) or large inequant crystals that lack preferred orientation

A

Granoblastic Texture

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37
Q

High grade rocks with such texture that form at elevate T&P considitions associated with deep BURIAL

A

Granulite

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38
Q

Shapes of crystals in Granoblastic textures

A

Anhedral wth sutured boundaries

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39
Q

What is the implication of such GrainShape

A

combination of
Pressure Sol’n
Recyrstallization
Annealing

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40
Q

a strain recovery process in which new unstrained, polygonal grains develop from and replace highly strained grains at high T

A

Annealing/Polygonization/Hot Working

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41
Q

Usual crystals/Minerals with Granoblastic textures

A

Qtz
felds
calc
(Crystals with low euhedral form potential and usually in subequant forms)
no phyllosilicates or tabular to prismatic minerals

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42
Q

A common met granoblastic rock with >90% qtz which is hard, durable and produce angular surfaces when fractured

A

Metaquartzite

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43
Q

Usual protolith of Metaquartzite

A

qtz-rich sandstone
chert

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44
Q

Common accessory minerals in qtzite

A

Hemat
Felds

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45
Q

What processes are involved in the formation of Metaquarztie

A

Recyrstallization
Pressure soln
Intercrystalline plastic deformation

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46
Q

Usuall appearance of metaquartzite that distinguishes it from granular quartzarenite

A

smooth and glazed appearance

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47
Q

Uses of quartzite

A

Rock walls, railroad ballast and dranaige culverts

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48
Q

Granoblastic met rocks rich in calcite and dolomite derived by recrystallization of limestone or dolostone protoliths

A

Marble

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49
Q

types of metamorphism which produces marble

A

Dynamothermal
Deep Burial, or
contact

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50
Q

Common accessory minerals which provde distinctive hues to marble

A

Graphite
Ca and Mg-rich minerals
Brucite, Diops ,Forste
Wollas, Epid, Serpentine, Idiocrase,
Temolite, Grossular

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51
Q

What colors can an iron oxide mineral give to a marble

A

Red or Yellow

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52
Q

Characteristic of marbles

A

Soft and Easy to Cut

53
Q

Granoblastic calc-silicate rocks formed by contact metamorphism of cabonate country rocks such as limestone or dolostones

54
Q

Another term for Skarns

55
Q

process responsible for the exchange of constituents between the pluton and the country rock

A

Metasomatism

56
Q

Usuall mineral assemblage of skarn

A

Calc, dolo, Ankerite, qtz
and calc-mg silicates

57
Q

Met rocks whith fractures, angular partices that forms in response to the brittle crushing of grains during deformation

A

Cataclastic rocks

58
Q

in which environment are cataclastic rocks form

A

Upper Crustal Fault Zone within 15 kms of Earth’s surface

59
Q

What type of metamorphism form cataclastic rocks

A

Dynamic met

60
Q

how are cataclastic texture described

A

with respect to:
relative percentages of Large Clasts and fine matrix
degree of cohesion

61
Q

Cataclastic rocks that
lack cohesion
coarse angular fragment >2mm

62
Q

cataclastic rocks that
lack cohesion
fine grained

63
Q

Derived from metamorphism of sed or ign breccias commonly developed during dynamoyherma or dynamic met which contain subangular to angular clasts with >2mm.
Grains are interlocked tighlty that rupture occurs through grains

A

Metabreccia

64
Q

Cohesive met rock with cataclastic textures produced by brittle deformation

A

Cataclasite

65
Q

Conditions at which cataclasite forms

A

Low Temp
High Strain
Dynamic Met Conditions
at Upper Crustal Fault Zones

66
Q

the ability to remain as a cohesive mass during deformation

A

Primary cohesion

67
Q

cataclasite with 10-50% matrix

A

Para-cataclastite

68
Q

cataclasite with 50-90% matrix

A

Cataclasite

69
Q

catactasite with 90-100% matrix

A

Ultracataclasite

70
Q

some facts about cataclasite

A

Serve as seals in faults zones
ruptures easily during fault reactivation

71
Q

glassy rocks produced by high strain rates generating LOCALIZED metling due to pressure release in fault zones
very dark-colored vitreous to flinty which occurs as vein material

A

Pseudotachylite

72
Q

High Strain Cataclastic Rocks created by SHORT TERM stresses associated with extraterrestrial bodies impacting the Earth

A

Impactites

73
Q

Produced by fragmentation of rock upon impact

A

Impact Breccia

74
Q

Glassy spherules that form as rocks are locally melted due to impact

75
Q

Form due to the intense stress that deform crystal structures especially common in “shocked”

A

Deformation lamellae

76
Q

Ultra high pressure mineral assemblages such as high-P silca

A

Coesite
Stishovite

77
Q

where was coesite first discovered?

A

Meteor crater

78
Q

What are the four components of impactites

A
  1. Impact Breccia
  2. Tektites
  3. Deformation Lamellae
  4. High PressureMinerals Assemblages
79
Q

Non-crystalline, high grade coals that form by heating, compression and chemically altering bituminous coal

A

Anthracites Coals

80
Q

Diagnostic properties of AC

A

Vitreous
Lt. weight
Jet Black color
Conchoidal Fracture

81
Q

Which have higer thermal capacity due to loss of volatiles?

A

Anthracite

82
Q

derived from conglomerate protoliths with sub-rounded to rounded relict clasts with >2mm diameters

A

Metaconglomerate

83
Q

Met associ with metaconglo

A

Deep Burial
Dynamothermal
Contact

84
Q

Where does rupture occur in an otherwise tightly interlocking grains

A

within or through grains rather than around them

85
Q

One type of clast conglo

A

Oligomictic

86
Q

Many clast types

A

Polymictic

87
Q

Metamorphism of conglo or breccias in response to STRONG NONUNIFORM Stresses during dynamic or dynamothermal metamorphism in which pebbles and cobbles are shorthened or flattend to the Z-strain direction and elongate to the X-strain in which pebble alignment may define lineation or foliation

A

Stretched Pebble Metaconglomerates

88
Q

Serpentine rich met rocks that occur in foliated and non-foliated form

A

Serpentinite

89
Q

process by which serpentinites form

A

Serpentinization

90
Q

How does serpentinization proceed

A

at temperatures below 500 deg cel, ultrabasic rocks, Oli and pyx are HYDRATED to form serpentine group of minerals

91
Q

Low temp serpentine minerals

A

Lizardite and Chrysotile

92
Q

High Temp mineral

A

Antigorite

93
Q

Environments of Serpentinization

A
  1. Ocean Spreading Ridges
  2. Subduction zones
94
Q

chaotic assemblage or rocks in subduction complexes

A

Tectonic Melanges

95
Q

Fine grained rocks that through alteration of ultrabasic rocks, or Mg-rich Sed rocks such as Dolostone by low temp and low pressure HF

A

Soapstones

96
Q

Mineral assemblage of soapstone

A

Talc w/ Magnesite, Serpentine and/or Tremolite

97
Q

Chacracteristic of Soapstone

A

Low Hardness
Wt. to green Color
Soapy Texture due to talc

98
Q

Green colored rocks rich in silicate minerals that commonly include in Chlorite, Epidote, Prehnite, Pumpellyite Tack, Serpentine, Actinolite and Albite

A

Greenstones

99
Q

Temp of alteration of basic and ultrabasic rocks to greenstones

A

200-500 deg cel

100
Q

What minerals are being altered during metamorphism to form greenstnone

A

Plag
ferromag (Oli, Pyx, Amph)

101
Q

What are the usual protoliths of Greenstones

A

Basalt and Gabbros

102
Q

Type of Met

A

Hydrotherma Metamorphism

103
Q

usuall site of greenstone formation

A

Oceanic crust near divergent plate boundaries

104
Q

Na-rich basalt

105
Q

Na-rich andesite

A

Keratophyres

106
Q

Large scale formation made up of greenstones usually of precambrian age and are synclinal

A

Greenstone Belts

107
Q

Usual sequence of Greenstone belts (T to B)

A

1Greywacke and Chert
2Intemediate and silicic metavolcanic and metavolcaniclastic sequences
3metabasalt
4Komatiites ultrabasic metavolcanic rocks

108
Q

This usually forms parallel greenstone belts and are granitic to dioritic composition metamorphosed at high T and Ps

A

Granulite Belts

109
Q

Best known greenstone localities in the world

A

Barberton Belt, SA
Eastern Goldfields W.Australia
Superior and Slave Provnices Nam
Sao Francisco Craton Brazil

110
Q

whats the implication of higher geothermal gradient during precambrian in subduction zones?

A

Higher grade metamoporhism at shallow depths and prevented deep subduction along steeply inclined benioff znones

111
Q

Dark-colored rocs composed largely of amphiboles such as horblende and plagioclases

A

Amphibolite

112
Q

Common Major mineral in Amphibolite

113
Q

Temp of formation of amphibolites during Regional Metamorphism (orogeny) of igneous rocks or sed rocks such as calcareous mudrocks and greywackes

A

> 550 deg cel

114
Q

Amphibolites with Basalt and Grabbro Protolith

A

Ortho-Amphibolites

115
Q

Amphibolites with Sed protolith

A

Para-Amphibolites

116
Q

Medium to coarse grained rocks with granoblastic to foliated texture

117
Q

high temp at which granulites are formed

118
Q

High pressure conditions at which granulites form

A

> 10Kbar approx 33km

119
Q

Whats the implication of high temp metamorphism

A

Dehydration of hydrous amphibole and mica to pyx, kfeds, kyanite and garnet

120
Q

what preserves the rocks’ metamorphic fabric

A

High Pressure
Low Water content

121
Q

Possible protoliths of Granulite

A

Gabbro
Peridotit
Pelitic Rocks (Mudstones, graywacke)

122
Q

With increasng temp what mineral transformation has been observed withing granulites

A

opx and plag transforms to Qtz, Cpx, garnet

123
Q

Very high pressure and high temp met rocks developed principally from basalt and gabbro protoliths

124
Q

In what part of the earth is eclogite may be a major rock type?

A

Earth’s Lower Crust

125
Q

T andP of Eclogite formation

A

> 400 deg cel
1.2 Gpa >40km

126
Q

Main mineral assemblage of Eclogite

A

Jadeite (Na,Al), Omphacite (Na,Ca) - Pyx
Garnet: Pyrope, Almandine, grossular

127
Q

Processes which may form Eclogite

A

1) High P crystallization of deep contnental crustal rocks duing thickening at continent-continent collision
2) Partial Melting of the mantle followed by deep crystallization as high pressure eclogite
3) High P Met of subducted oceanic lithosphere deep within the earth

128
Q

Density of Eclogite which may be the driving force of mantle convection and plate motion

A

3.5-40 g/cc

GLE 2024 (Day 2) (41 decks)

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