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

METAMORPHIC PETROLOGY (FOLIATED METAMORPHIC ROCKS) Flashcards

1
Q

Inequant crystals of what minerals form foliation?

A

Tabular - Phyllosilicates
Primsatic/Accicular - Inosilicate

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2
Q

Type of Metamorphism which causes foliation

A

Dynamic
Dynamothermal

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3
Q

Foliated Textures

A

Slaty Cleavage
Phyllitic Cleavage
Schistocity
Gneissic Layering
Migmatitic Layering
Mylonitic Foliation

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4
Q

Fine grained
Al-rich
Pelitic
w/ flat planar cleavage

A

Slate

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5
Q

Closely spaced layers along w/c rock breaks or cleaves readily to produce flat surfaces with a DULL Luster

A

Slaty Cleavage

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6
Q

Low temp at which slate forms from Shale, Siltsone, Mudstone or Tuff

A

150-250 deg cel

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7
Q

What happens to phyllosilicate minerals during the formation of slates?

A

Reoriented perpendicular to the maximum shortening direction

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8
Q

With increasing temp these minerals deacreases

A

Clay Minerals (Kaolinite, Smectite)
Zeolite Minerals

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9
Q

With increasing temp these minerals increases in abundance

A

Illite
Chlorite
Mica

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10
Q

Accessory Minerals

A

Qtz, Graphite, Pyr, Ilmenite, Chlorite
Plag, and Fe Ox Hematite

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11
Q

Uses of Slates

A

Construction Application
Sidewalks
Roof Shingles
School Blackboards
Pool Tables
Patos and Tiles

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12
Q

This rocks display Phylittic Cleavage which has silky and glossy sheen compared to Slate

A

Phyllite

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13
Q

What is the disctinction of Phyllitic Cleavage to Slaty Cleavage?

A

Has Wavy Surface

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14
Q

How do Phyllites Form?

A

Recrystallization of Slates at Temp >250deg

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15
Q

Temps at which Phyllite form

A

250-300

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16
Q

Smectite and Illite gradei metamorphose to slightly corases grained minerals such as

A

Sericite
Muscovite
Talc
Chlorite

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17
Q

Phyllites display this kind of cleavage which crosscuts an earlier generation of cleaveage

A

Crenulation Cleavage

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18
Q

A very common less regular foliation defined by sub-parallel arrangement of Macroscopic Platy Minerals such as Phyllosilicates in closely spaced met layers.
And appears to have high sheen or sparkle due to presence of light reflecting crystals

A

Schistocity

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19
Q

Rocks which schows Schistocity

A

Schist

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20
Q

In Schist, Qtz and felds are

A

Flattened

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21
Q

In Schists, less competent minerals such as mica are commonly

A

Stretched and folded

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22
Q

Environment of Schisct formation

A

Convergent plate boundaries
>300 deg cel

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23
Q

Implication of such environment of formation

A

Brittle + ductile deformation
Qtz begin to deform plastically
Felds remain rigid

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24
Q

what forms at such moderate to high temp and non uniform stress?

A

Visible Porphyroclasts
Porphyroblasts

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25
Q

Schists are rich in (Hydrous, anhydrous) minerals

A

Hydrous

26
Q

At this temperature, Hydrous minerals become unstable (talc and chlorite) and anyhydrous minerals form

A

> 400 deg cel

27
Q

Foliation characterized by the arrangement of minerals into distinct color bands

A

Gneissocity or Gneissic Layering

28
Q

Usual Accessory Minerals in Gneisses

A

Garnet
Sillimanite
Cordierite
Corundum

29
Q

Gneiss with Oval eye-shaped crystals of rigid feldspars

A

Augen Gneiss

30
Q

Gneisses with igneous Protoliths

A

Orthogneiss

31
Q

Gneisses formed from Sed Protolith

A

Paragneiss

32
Q

Gabbro-derived Gneiss

A

Mafic Gneiss

33
Q

Granite-derived Gneiss

A

Granitic Gneiss

34
Q

This results from the pulling apart of earlier folded layers resulting in the separation of hinges and limbs

A

Transposition

35
Q

Minerals which are concentrated in the fold limbs

A

Phyllosilicates and Inosilicates

36
Q

Minerals which are concentrated in the fold hinges

A

Qtz and Feldspars

37
Q

Mechanisms/Processes attributed to Gneissic Layering

A

1 Tranposition
2 Anatexis
3. Lit par lit intrusion

38
Q

Refers to sill-like intrusion of magma into parallel country rock layers anc can occur to a limited extent when granitic magma intrudes mafic country rocks

A

Lil par lit Intrusion

39
Q

These structures may be preserved in gneisses

A

Igneous Textures

40
Q

Temp at which extensive melting of gneiss can lead to the disassembly of gneissic banding and formation of migmatite

A

> 700 deg cel

41
Q

Mixed rocks that possess textural and structural characteristics of both ign and met rocks which display an irregular, swirling mix of colors. Resembles rocks with Gneiss and dark colored component rich in pyroxene

A

Migmatites

42
Q

Environment of formation of Migmatite

A

Convergent plate boundaries

43
Q

Metamorphism related to Migmatite formation

A

Dynamothermal Metamorphism

44
Q

Processes involve in Migmatite Formation

A

1.Anatexis
2. Magma Injectio
3. Ductile Deformation or Plastic Flow in lower crust

45
Q

Silica and iron rich rocks

A

Ironstones

46
Q

in which geologic time are ironstones restricted

A

Archean to E.Proterozoic

47
Q

IN BIFs the black layers are

A

Magnetite and Hematite (Iron Oxides)

48
Q

The red layers are

A

Cherts

49
Q

Metaquartzites that contains 20-30% iron and are also commonly banded

A

Taconites

50
Q

Fine-grained foliated rocks produced in the ductile shear zones of the lower crust and Upper mantle

A

Mylonites

51
Q

In ductile shear zones, deformation includes

A

Crushing and Grinding (Cataclasis)
Plastic Flows

52
Q

During ductile shearing, grains are elongated

A

parallel to shear zones

53
Q

A signature component of mylonites associated with High Temp and Press in the lower crust and mantle

A

Intensely sheared and recyrstallized Porphyroclasts and/or neocrystallized prophyroblasts

54
Q

Mylonites are classfied based on

A

Relative percentage of matrix material

55
Q

10-50% matrix

A

Protomylonite

56
Q

50-90% matrix

A

Mylonites

57
Q

90-100% matrix

A

Ultramylonite

58
Q

Implication of higher matrix percentatge

A

Greater intensity of grain size reduction and more instense shear strains

59
Q

Pervasively deformed rocks so that their originial composition and texture are largely obliterated and are defined by their SOLID STATE FLOW FABRIC generated through intense ductile or brittle-ductile deformation

A

Tectonites

60
Q

Foliated tectonites

A

s-tectonites

61
Q

Tectonites with lineation but no foliation

A

L-tectonites

62
Q

Tectonites with both Lineation and Foliation

A

L-S Tectonites

GLE 2024 (Day 2) (41 decks)

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