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Atoms to volcanoes - 33739 > Metamorphic petrology - L2 > Flashcards

Metamorphic petrology - L2 Flashcards

1
Q

What characteristics are used to classify metamorphic rocks?

A

Texture
Fabric
Composition

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2
Q

How are metamorphic rocks commonly named?

A

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

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3
Q

How can the fabric of metamorphic rocks be described?

A

foliated / weakly foliated / non-foliated

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4
Q

What forms can foliations be found in?

A

cleavage
schistosity- preferred orientation of elongated or platy grains
banding

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5
Q

What are the protolith for magmatic and sedimentary?

A

Magmatic- Ortho
Sedimentary- Para

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6
Q

How can mineral content be used to identify metamorphic rocks?

A

based on the prevailing mineral

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7
Q

What factors can be used to for classifying metamorphic rocks?

A

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

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8
Q

What is foliation?

A

any planar fabric element, generally formed by platy minerals

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9
Q

What rocks show examples of foliation?

A

Mica
Chlorite

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10
Q

What are rocks with foliation also called?

A

S-tectonites

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11
Q

What is lineation?

A

any linear fabric element generally formed by elongated minerals

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12
Q

What rocks show examples of lineation?

A

Pyroxenes
Amphibole
Tourmaline

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13
Q

What can rocks with lineation also be called?

A

L-tectonites

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14
Q

What are S-L tectonites?

A

Rocks with both foliation and lineation

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15
Q

What does pressure do to minerals undergoing metamorphism?

A

rotates and realigns

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16
Q

What texture is produced by foliation?

A

lepidoblastic

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17
Q

What is lepidoblastic texture like?

A

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

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18
Q

Where does lineation typically occur?

A

shear zones- minerals realign parallel to shear sense

19
Q

What texture is defined by lineation?

A

nematoblastic texture

20
Q

What is a nematoblastic texture like?

A

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

21
Q

What is slaty cleavage?

A

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

22
Q

What is slaty cleavage yielded by?

A

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

23
Q

What texture is produced from slaty cleavage?

A

Aphanitic texture (small crystals cant be seen by eye)

24
Q

What texture will rocks with a slaty texture have?

A

lepidoblastic

25
Q

What are the characteristics of slate?

A

Compact,
very fine-grained,
well-developed cleavage

26
Q

What are the characteristics of Phyllite?

A

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

27
Q

What is schistosity?

A

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

28
Q

What will the grain size from schistosity be?

A

coarse grained enough to see with the unaided eye

29
Q

What will the fabric of schistosity be?

A

planar but lineation’s may be present

30
Q

What is a schist?

A

metamorphic rock exhibiting a schistosity

31
Q

What is a gneiss?

A

metamorphic rock displaying gneissose structure

32
Q

What is a gneissose structure?

A

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

33
Q

What are typical non-foliated rocks created by?

A

contact metamorphism

34
Q

What are Granofels?

A

general term for metamorphic rock with granoblastic texture

35
Q

What is a granoblastic texture like?

A

equidimensional, anhedral grains with no preferred orientation

36
Q

What is a hornfel?

A

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

37
Q

How is a granoblastic texture formed?

A

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

38
Q

What is a Porphyroblastic texture?

A

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

39
Q

What is each individual crystal in porphyroblastic texture called?

A

porphyroblast

40
Q

What is an augen gneiss?

A

a gneiss with an augen texture

41
Q

What is an augen texture?

A

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

42
Q

What are the individual grains in an augen gneiss called?

A

auge

43
Q

What is a metamorphic facie?

A

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

Atoms to volcanoes - 33739 (16 decks)

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