Metamorphic petrology - L2

Question 1

What characteristics are used to classify metamorphic rocks?

Answer 1

Texture
Fabric
Composition

Question 2

How are metamorphic rocks commonly named?

Answer 2

have a prefix-type modifier and then name to show textural or mineralogical aspect

Question 3

How can the fabric of metamorphic rocks be described?

Answer 3

foliated / weakly foliated / non-foliated

Question 4

What forms can foliations be found in?

Answer 4

cleavage
schistosity- preferred orientation of elongated or platy grains
banding

Question 5

What are the protolith for magmatic and sedimentary?

Answer 5

Magmatic- Ortho
Sedimentary- Para

Question 6

How can mineral content be used to identify metamorphic rocks?

Answer 6

based on the prevailing mineral

Question 7

What factors can be used to for classifying metamorphic rocks?

Answer 7

Fabric
Protolith
Mineral content
Geological setting/ nature of metamorphism
Metamorphic grade
Metamorphic facies

Question 8

What is foliation?

Answer 8

any planar fabric element, generally formed by platy minerals

Question 9

What rocks show examples of foliation?

Answer 9

Mica
Chlorite

Question 10

What are rocks with foliation also called?

Answer 10

S-tectonites

Question 11

What is lineation?

Answer 11

any linear fabric element generally formed by elongated minerals

Question 12

What rocks show examples of lineation?

Answer 12

Pyroxenes
Amphibole
Tourmaline

Question 13

What can rocks with lineation also be called?

Answer 13

L-tectonites

Question 14

What are S-L tectonites?

Answer 14

Rocks with both foliation and lineation

Question 15

What does pressure do to minerals undergoing metamorphism?

Answer 15

rotates and realigns

Question 16

What texture is produced by foliation?

Answer 16

lepidoblastic

Question 17

What is lepidoblastic texture like?

Answer 17

metamorphic texture in which platy or tabular minerals are aligned to produce a planar fabric

Question 18

Where does lineation typically occur?

Answer 18

shear zones- minerals realign parallel to shear sense

Question 19

What texture is defined by lineation?

Answer 19

nematoblastic texture

Question 20

What is a nematoblastic texture like?

Answer 20

almost looks like a bunch of straws tied together facing same direction

Question 21

What is slaty cleavage?

Answer 21

property of a rock to split along a regular set of sub-parallel planes

Question 22

What is slaty cleavage yielded by?

Answer 22

preferred alignment of phyllosilicates (i.e., chlorite, mica, etc.) due to tectonic stress

Question 23

What texture is produced from slaty cleavage?

Answer 23

Aphanitic texture (small crystals cant be seen by eye)

Question 24

What texture will rocks with a slaty texture have?

Answer 24

lepidoblastic

Question 25

What are the characteristics of slate?

Answer 25

Compact, very fine-grained, well-developed cleavage

Question 26

What are the characteristics of Phyllite?

Answer 26

Coarser grain with a shiny cleavage made by fine phyllo-silicates May have both foliation and lineation

Question 27

What is schistosity?

Answer 27

preferred orientation of mineral grains or grain aggregates produced by metamorphic processes

Question 28

What will the grain size from schistosity be?

Answer 28

coarse grained enough to see with the unaided eye

Question 29

What will the fabric of schistosity be?

Answer 29

planar but lineation's may be present

Question 30

What is a schist?

Answer 30

metamorphic rock exhibiting a schistosity

Question 31

What is a gneiss?

Answer 31

metamorphic rock displaying gneissose structure

Question 32

What is a gneissose structure?

Answer 32

coarse grained with layering composed of alternating felsic (white) and mafic (darker) mineral layers

Question 33

What are typical non-foliated rocks created by?

Answer 33

contact metamorphism

Question 34

What are Granofels?

Answer 34

general term for metamorphic rock with granoblastic texture

Question 35

What is a granoblastic texture like?

Answer 35

equidimensional, anhedral grains with no preferred orientation

Question 36

What is a hornfel?

Answer 36

type of granofels that is typically very fine-grained and compact, and occurs in contact aureoles

Question 37

How is a granoblastic texture formed?

Answer 37

equidimensional grains with straight edged frequently forming a triple junction at 120°

Question 38

What is a Porphyroblastic texture?

Answer 38

metamorphic rocks that have one or more metamorphic minerals that grew much larger than the others.

Question 39

What is each individual crystal in porphyroblastic texture called?

Answer 39

porphyroblast

Question 40

What is an augen gneiss?

Answer 40

a gneiss with an augen texture

Question 41

What is an augen texture?

Answer 41

large eye-shaped grains derived from sheared pre-existing large crystals

Question 42

What are the individual grains in an augen gneiss called?

Answer 42

auge

Question 43

What is a metamorphic facie?

Answer 43

a range of P-T conditions over which a mineral assemblage is stable (P-T or pressure temp)