1.4 Metamorphic Rocks and Processes Flashcards

1
Q

What are metamorphic rocks a result of?

A

Increased temperature and/or pressure on existing rock - causing recrystallisation to form new minerals and textures

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2
Q

Which metamorphic rocks are crystalline?

A

All of them

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3
Q

Difference between lamination and foliation?

A
  • lamination used for sedimentary rocks

* foliation used for metamorphic rocks

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4
Q

Description of marble?

A
  • crystalline

* 1mm crystals

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5
Q

Description of schist?

A
  • crystalline
  • 1-5 mm crystals
  • layered - foliated
  • mica and possibly garnet
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6
Q

Description of slate?

A
  • crystalline
  • crystals too small to measure
  • foliation >0.5 mm thick
  • mica and small amounts of quartz
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7
Q

What gives slate its cleavage?

A

Mica

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8
Q

Description of chiastolite slate?

A
  • crystalline
  • white specs - chiastolite (mineral)
  • 10-20 mm crystals
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9
Q

Description of gneiss?

A
  • crystalline
  • pink crystals
  • large crystals - 1-20 mm
  • foliated - big layers
  • mica, quartz, orthoclase feldspar (pink) and plagioclase (white)
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10
Q

Description of metaquartzite?

A
  • crystalline
  • crystals so big you can’t see - when you can see crystals 1 mm
  • quartz
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11
Q

What factors control metamorphism?

A
  • heat
  • pressure
  • time
  • parent rock
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12
Q

What are the main agents of metamorphism?

A

Heat and pressure

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13
Q

What effect will greater heat have during metamorphism?

A

Larger crystals

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14
Q

What effect will greater pressure have during metamorphism?

A

Rock will have layering or foliation - pressure at right angles to the foliation

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15
Q

What are the two types of metamorphism?

A
  • thermal or contact

* regional

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16
Q

What does thermal/contact metamorphism usually form?

A

An area of baked rocks called a metamorphic aureole

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17
Q

What is a metamorphic aureole?

A

An area of baked rocks

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18
Q

What agent does thermal metamorphism involve?

A

Just heat

19
Q

Where does the heat come from usually in thermal metamorphism?

A

Bodies of magma

20
Q

As a rock progresses closer to a granite intrusion, what happens in terms of thermal metamorphism?

A
  • limestone becomes marble

* shale becomes slate, then schist, then gneiss

21
Q

What agents does regional metamorphism involve?

A

Heat and pressure

22
Q

What is regional metamorphism usually a result of?

A

Earth movements over a wide area

23
Q

What are rocks formed by regional metamorphism divided into?

A

Low, medium and high grade - depending on the temperature and pressure in which they were formed

24
Q

Difference between rocks formed by thermal and regional metamorphism?

A

Regionally metamorphosed rocks will show foliation due to pressure, while thermally will not

25
Q

Which metamorphic rock is formed under low pressure and high temperatures?

A

Marble

26
Q

Which metamorphic rock is formed under relatively low pressures and low temperatures?

A

Slate

27
Q

Which metamorphic rock is formed under high pressure and high temperatures?

A
  • schist

* chiastolite slate

28
Q

What rocks are formed by contact or thermal metamorphism?

A

Marble

29
Q

What rocks are formed by regional metamorphism?

A
  • slate
  • schist
  • gneiss
30
Q

What rocks are formed by contact and regional metamorphism?

A

Chiastolite slate

31
Q

What mineral can be seen in marble?

A

Calcite

32
Q

What mineral can be seen in schist?

A

Mica, garnet

33
Q

What mineral can be seen in slate?

A

Mica, quartz

34
Q

What mineral can be seen in chiastolite slate?

A

Chiastolite, mica (dominant) and quartz (less dominant)

35
Q

What is the parent rock of marble?

A

Limestone

36
Q

What is the parent rock of schist?

A

Shale

37
Q

What is the parent rock of slate?

A

Shale

38
Q

What is the parent rock of chiastolite slate?

A

Shale

39
Q

Which minerals are most easily changed due to metamorphism?

A

Clay minerals (that make up shale) are most easily changed

40
Q

If there is a lot of folding in a rock, what does this suggest about the conditions it was formed under?

A

Formed under high pressures

41
Q

Examples of metamorphic rocks?

A
  • schist
  • marble
  • slate
  • metaquartzite
42
Q

What does low-grade regional metamorphism involve?

A

High pressure but relatively low temperatures

43
Q

What does medium-grade regional metamorphism involve?

A

Occurs during development of mountain chains - high pressure and moderately high temperatures

44
Q

What does high-grade regional metamorphism involve?

A

Takes places at depth during formation of mountain chains - intense pressure and heat