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Geo1111 > Lecture 9: Metamorphic Rocks > Flashcards

Lecture 9: Metamorphic Rocks Flashcards

1
Q

Metamorphism

A 
A process by which:
Temperature
Pressure &
Chemical Reactions
alters:
Mineral content &
Structure 
Of pre-existing rock(without melting and solid state only)
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2
Q

Metamorphic rocks are produced from:

A

Potential protoliths:
Igneous rocks
Sedimentary rocks &
Other metamorphic rocks

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3
Q

What type of changes do protoliths undergo?

A

They undergo changes in texture and mineralogy due to variations in temperature, pressure, tectonic stress, and the amount of reactive water.

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4
Q

What is the example of metamorphosis?

A

Limestone metamorphosizes into marble

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5
Q

Slide

A

6,7,8

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6
Q

Foliation

A

A planar fabric that cuts through the rock and is defined by the alignment of platy minerals or creation of alternating light and dark bands.
A set of flat or wavy parallel planes produced by directed pressure/deformation.

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7
Q

Provide an example of platy minerals

A

Mica

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8
Q

Metamorphosis often imparts ________ upon new rocks

A

Foliation

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9
Q

What is the most common textural feature of metamorphic rocks?

A

Foliation

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10
Q

Foliation vs lineation

A

Slide 10

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11
Q

Metamorphic processes:

A
  1. Recrystallization:
  2. Neo-crystallization:
  3. Pressure Solution:
  4. Plastic Deformation: (no squiggly lines or sharp edges nothing was dissolve or deposited elsewhere)
  5. Overprinting:
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12
Q

Which parameters control metamorphism?

A

Temperature
Pressure
Hydrothermal fluids

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13
Q

Describe the control of temperature on metamorphism.

A

The change in temperature is what is key to look at not absolute. Temperature ranges from 250 to 850 degrees Celsius which varies with tectonic setting. The sources of heat are from geothermal gradients, magnetic intrusions, or tectonic compression.
Slide 16

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14
Q

Describe the metamorphic process: recrystallization provide an example.

A

the minerals change size and shape through dissolution and growth of crystals. The composition of the minerals does not change, however. Example: limestone has tiny clasts (protolith) → marble has large, new grains (metamorphic rock)

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15
Q

Solid solution vs polymorphs **MIDTERM**

A

Exam question slides: 18

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16
Q

Polymorphs

A

Slide 18

17
Q

Pressure in metamorphism

A

Pressure:

  • lithostatic or confining: pressure pushes rock equally from all directions to become more dense and retain same shape
  • directed: pressure is greatest in one specific direction resulting in a change in shape and the new mineral growth aligns perpendicular to pressure equal to folation
18
Q

Stress in metamorphism

A

Slides:20-29

19
Q

Hydrothermal fluid in metamorphism

A

Hydrothermal fluid (hot water with dissolved ions and volatiles) accelerates metamorphism. Hydrothermal fluids speed up chemical reactions which add or subtract elements. Hydrothermal alteration is called metasomatism.

20
Q

Is metamorphosis isochemical? What is its non-isochemical name?

A

Yes; metasomatism

21
Q

Metasomatism

A

Hydrothermal alteration from accelerated metamorphism by hydrothermal fluid

22
Q

Classifications of metamorphic rocks

A

Foliated rocks:
Granoblastic rocks:
Slide 31

23
Q

Foliated Metamorphic Rocks increasing by temp.

A 
(200-300): Slate
(300-400): Phyllite
Metaconglomerate: metamorphosed conglomerate 
(400-600): Schist
(>650): Gneiss
(>750): Migmatites
24
Q

Non foliated rocks are called

A

Granoblastic rocks

25
Q

Non foliated rock types

A

Quartzite, and marble

26
Q

Metamorphic grade

A

A measure of the intensity of temp and pressure conditions that lead to alteration of metamorphic rocks from pelitic (clay-rich) protolith

27
Q

The metamorphic grade displays that different temperature and pressure conditions occur in different ___

A

Geological settings

28
Q

Slides

A

49-53

29
Q

Geothermal gradient in metamorphism

A

Occurs in different settings that have different characteristics of :

  1. heat flow
  2. differential stress &
  3. hydrothermal fluid interaction.
30
Q

Slides

A

55

31
Q

Types of metamorphism

A 
1. Thermal: heating by a
plutonic intrusion 
2. Burial: deep burial in a
basin 
3. Dynamic: shearing in a
fault zone 
4. Regional: P and T change
due to orogenesis 
5. Hydrothermal: alteration
by hot water leaching 
6. Subduction: high P and
low T alteration •
7. Shock: extreme high P
from a bolide impact
32
Q

Types of geological settings in metamorphism

A
  1. Contact metamorphism
  2. Dynamic metamorphism
  3. Regional metamorphism
  4. Burial metamorphism
  5. Hydrothermal metamorphism
  6. Subduction metamorphism

Geo1111 (8 decks)

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