METAMORPHIC PETROLOGY (FOLIATED METAMORPHIC ROCKS)

Question 1

Inequant crystals of what minerals form foliation?

Answer 1

Tabular - Phyllosilicates
Primsatic/Accicular - Inosilicate

Question 2

Type of Metamorphism which causes foliation

Answer 2

Dynamic
Dynamothermal

Question 3

Foliated Textures

Answer 3

Slaty Cleavage
Phyllitic Cleavage
Schistocity
Gneissic Layering
Migmatitic Layering
Mylonitic Foliation

Question 4

Fine grained
Al-rich
Pelitic
w/ flat planar cleavage

Answer 4

Slate

Question 5

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

Answer 5

Slaty Cleavage

Question 6

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

Answer 6

150-250 deg cel

Question 7

What happens to phyllosilicate minerals during the formation of slates?

Answer 7

Reoriented perpendicular to the maximum shortening direction

Question 8

With increasing temp these minerals deacreases

Answer 8

Clay Minerals (Kaolinite, Smectite)
Zeolite Minerals

Question 9

With increasing temp these minerals increases in abundance

Answer 9

Illite
Chlorite
Mica

Question 10

Accessory Minerals

Answer 10

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

Question 11

Uses of Slates

Answer 11

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

Question 12

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

Answer 12

Phyllite

Question 13

What is the disctinction of Phyllitic Cleavage to Slaty Cleavage?

Answer 13

Has Wavy Surface

Question 14

How do Phyllites Form?

Answer 14

Recrystallization of Slates at Temp >250deg

Question 15

Temps at which Phyllite form

Answer 15

250-300

Question 16

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

Answer 16

Sericite
Muscovite
Talc
Chlorite

Question 17

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

Answer 17

Crenulation Cleavage

Question 18

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

Answer 18

Schistocity

Question 19

Rocks which schows Schistocity

Answer 19

Schist

Question 20

In Schist, Qtz and felds are

Answer 20

Flattened

Question 21

In Schists, less competent minerals such as mica are commonly

Answer 21

Stretched and folded

Question 22

Environment of Schisct formation

Answer 22

Convergent plate boundaries
>300 deg cel

Question 23

Implication of such environment of formation

Answer 23

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

Question 24

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

Answer 24

Visible Porphyroclasts
Porphyroblasts

Question 25

Schists are rich in (Hydrous, anhydrous) minerals

Answer 25

Hydrous

Question 26

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

Answer 26

>400 deg cel

Question 27

Foliation characterized by the arrangement of minerals into distinct color bands

Answer 27

Gneissocity or Gneissic Layering

Question 28

Usual Accessory Minerals in Gneisses

Answer 28

Garnet Sillimanite Cordierite Corundum

Question 29

Gneiss with Oval eye-shaped crystals of rigid feldspars

Answer 29

Augen Gneiss

Question 30

Gneisses with igneous Protoliths

Answer 30

Orthogneiss

Question 31

Gneisses formed from Sed Protolith

Answer 31

Paragneiss

Question 32

Gabbro-derived Gneiss

Answer 32

Mafic Gneiss

Question 33

Granite-derived Gneiss

Answer 33

Granitic Gneiss

Question 34

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

Answer 34

Transposition

Question 35

Minerals which are concentrated in the fold limbs

Answer 35

Phyllosilicates and Inosilicates

Question 36

Minerals which are concentrated in the fold hinges

Answer 36

Qtz and Feldspars

Question 37

Mechanisms/Processes attributed to Gneissic Layering

Answer 37

1 Tranposition 2 Anatexis 3. Lit par lit intrusion

Question 38

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

Answer 38

Lil par lit Intrusion

Question 39

These structures may be preserved in gneisses

Answer 39

Igneous Textures

Question 40

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

Answer 40

>700 deg cel

Question 41

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

Answer 41

Migmatites

Question 42

Environment of formation of Migmatite

Answer 42

Convergent plate boundaries

Question 43

Metamorphism related to Migmatite formation

Answer 43

Dynamothermal Metamorphism

Question 44

Processes involve in Migmatite Formation

Answer 44

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

Question 45

Silica and iron rich rocks

Answer 45

Ironstones

Question 46

in which geologic time are ironstones restricted

Answer 46

Archean to E.Proterozoic

Question 47

IN BIFs the black layers are

Answer 47

Magnetite and Hematite (Iron Oxides)

Question 48

The red layers are

Answer 48

Cherts

Question 49

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

Answer 49

Taconites

Question 50

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

Answer 50

Mylonites

Question 51

In ductile shear zones, deformation includes

Answer 51

Crushing and Grinding (Cataclasis) Plastic Flows

Question 52

During ductile shearing, grains are elongated

Answer 52

parallel to shear zones

Question 53

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

Answer 53

Intensely sheared and recyrstallized Porphyroclasts and/or neocrystallized prophyroblasts

Question 54

Mylonites are classfied based on

Answer 54

Relative percentage of matrix material

Question 55

10-50% matrix

Answer 55

Protomylonite

Question 56

50-90% matrix

Answer 56

Mylonites

Question 57

90-100% matrix

Answer 57

Ultramylonite

Question 58

Implication of higher matrix percentatge

Answer 58

Greater intensity of grain size reduction and more instense shear strains

Question 59

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

Answer 59

Tectonites

Question 60

Foliated tectonites

Answer 60

s-tectonites

Question 61

Tectonites with lineation but no foliation

Answer 61

L-tectonites

Question 62

Tectonites with both Lineation and Foliation

Answer 62

L-S Tectonites