Metamorphism

Question 1

Name the 5 types of change that create metamorphic rocks.

Answer 1

1. Recrystallization
2. Phase change
3. Metamorphic reaction/neocrystallization
4. Pressure solution
5. Plastic deformation

Question 2

Metamorph means…

Answer 2

Meta = Change Morph = Form

Question 3

The preexisting rocks that are altered during metamorphism are called…

Answer 3

Protoliths

Question 4

Red shale’s (Protolith) metamorphic rock is?

Answer 4

Gneiss

Question 5

planar fabric that cuts through the rock

Answer 5

Foliation

Question 6

What is marble’s protolith?

Answer 6

Limestone

Question 7

The agents of metamorphism are:

Answer 7

heat (T), pressure (P), compression and shear, and hydrothermal (hot water) fluids

Question 8

Metamorphism occurs between what temperature ?

Answer 8

250-850 degrees Celcius

Question 9

What is metamorphic grade?

Answer 9

measure of the intensity of T and P conditions that lead to alteration

Question 10

What is hydrothermal alteration? Another name?

Answer 10

Hydrothermal fluids speed up chemical reactions and add or subtract elements. Also called: metasomatism

Question 11

Why does foliation occur?

Answer 11

because the rocks have been subjected to compression and/or shear and they have a significant component of platy minerals

Question 12

Compression is…

Answer 12

a stress that is greater in one direction

Question 13

How are compression and pressure different?

Answer 13

Compression is a stress that is greater in one direction.

Pressure is a stress that is of equal magnitude in all directions.

Question 14

Equant vs. Inequant

Answer 14

Roughly equal in all directions vs. dimensions are not all the same

Question 15

What are the two subdivisions of metamorphic rocks?

Answer 15

Foliated and non-foliated

Question 16

Non-foliated rocks

Answer 16

have no planar fabric evident because they lack inequant minerals and/or they recrystallized without differential stress

Question 17

Slate…

Answer 17

is a fine-grained, low-grade metamorphic shale. It has a distinct foliation called slaty cleavage.

Question 18

a fine-grained mica-rich rock that forms by the metamorphic alteration of slate. With further alteration, this turns into schist.

Answer 18

Phyllite

Question 19

A fine to coarsely crystalline rock with larger micas indicating medium-to high-grade metamorphism. It has a distinct foliation from large micas called schistosity.

Answer 19

Schist

Question 20

Gneiss

Answer 20

has distinct compositional bands, composed of light bands of felsic minerals (quartz and feldspars) alternating with dark bands of mafic minerals (biotite or amphibole).

Question 21

What is a migmatite?

Answer 21

a partially melted gneiss; it has features of both igneous and metamorphic rocks.

Question 22

Light-colored minerals that melt at lower T.

Dark-colored minerals that melt a higher T.

Answer 22

Felsic

Mafic

Question 23

a fine-grained rock from the baked margin of plutonic intrusions. It is often extremely hard and durable.

Answer 23

Hornfels

Question 24

What do non-foliated rocks lack?

Answer 24

A planar fabric

Question 25

Quartzite is a metamorphic rock of…

Answer 25

Quartz sandstone (protolith)

Question 26

A metamorphic facies is…

Answer 26

a set of mineral assemblages that indicate a certain range

of P and T conditions

Question 27

Blueschist metamorphism is associated with what type of plate boundary?

Answer 27

ocean crust subducting beneath a continent

Question 28

Contact metamorphism typically produces metamorphic rocks that are called …?

Answer 28

Hornfels