Deck 7: Metamorphism and Metamorphic Rocks

Question 1

What are the three types of pressures in the metamorphic process?

Answer 1

The three types being: (1) compressional: forces operating in same directions; (2) tensional: forces operating in opposite directions; (3) shear: forces pushing one part of the rock in one direction and one part in another.

Question 2

Describe the occurrence of metamorphism along a divergent plate boundary.

Answer 2

Magma rises at mid-oceanic ridges and heats the adjacent rocks, resulting in contact metamorphism. Fluids emanate from the rising magma, and the magma reacts with seawater to form hydrothermal solutions rich in some metals.

Question 3

Describe nonfoliated metamorphic rocks. What is their appearance? Describe the two types of nonfoliated metamorphic rocks.

Answer 3

In nonfoliated metamorphic rocks, the mineral grains appear as a mosaic of roughly equidimensional minerals. These rocks can be composed mainly of one mineral with visible grains, such as marble or quartzite, or of different grains that are too small to see without magnification, such as greenstone and hornfels.

Question 4

What are metamorphic zones based on? How are rocks within the same metamorphic zone similar to each other?

Question 5

Why is time important to metamorphic processes?

Question 6

What is a metamorphic facies and how are metamorphic facies named?

Question 7

What are the sources of the heat, pressure, and fluids that cause rocks to metamorphose?

Question 8

What are some uses of metamorphic rocks, such as marble, slate, talc, graphite, and clay?

Question 9

Is it always possible to identify the parent rock when looking at a metamorphic rock? Why or why not?

Question 10

What is the role of heat as an agent of metamorphism? What are the heat sources available for the formation of metamorphic rocks?

Question 11

Describe how contact metamorphism occurs. What are the important factors that cause rocks to alter in this type of metamorphism?

Question 12

Describe the occurrence of metamorphism along an oceanic-continental convergent plate boundary.

Question 13

What are index minerals and their importance? Give an example of minerals that would be found in low-grade, intermediate, and high-grade metamorphosed shale.

Question 14

How do metamorphic processes form ore deposits? What are some of the ores that are formed?

Question 15

Describe the characteristics of marble. How does it form, and what is it used for?

Question 16

Describe regional metamorphism. Where does it take place?

Question 17

Describe metamorphism in an aureole. Draw and label a picture of metamorphism surrounding a granite pluton to show the zones that might surround an intrusion.

Question 18

How are foliated metamorphic rocks classified? Describe some of the rock types found at different grades of foliated metamorphic rocks.

Question 19

What is metamorphic grade? Present an example of how a rock reaches its metamorphic grade.

Question 20

How are metamorphic rocks classified? What are the two main classifications, and how are they different from each other?

Question 21

How are metamorphic facies defined or recognized?

Question 22

What is a metamorphic facies?

Question 23

What causes dynamic metamorphism and where is it found?

Question 24

Metamorphism can be caused by increased temperatures. How are temperatures raised geologically to bring about metamorphism?

Question 25

What are some examples of foliated metamorphic rocks?

Question 26

What does increasing grade of metamorphism mean in terms of the conditions that produced a sequence of metamorphic rocks?

Question 27

Study Figure 7.18 in the text. How must conditions change for a rock to go from an amphibolite to an eclogite facies? What happens if pressure is at 4 kbar but temperature decreases from 600°C to 400°C?

Question 28

What is lithostatic pressure?

Question 29

What is an aureole?

Question 30

What are three possible sources of the water and other fluids that are active in metamorphism?

Question 31

What are some examples of nonfoliated metamorphic rocks?

Question 32

What is the difference between slate and phyllite?

Question 33

Why is time important in metamorphism?

Question 34

Foliated metamorphic rocks are further classified on the basis of what observable properties?

Question 35

What is the significance of foliation in a metamorphic rock? (Not what is foliation, but what does it mean in terms of the rock's history?)

Question 36

What is a metamorphic zone?

Question 37

Some of the oldest known rocks, which have been dated at about 4.0 billion years, are metamorphic. What does this tell us about the age of Earth?

Question 38

How can fluid activity promote metamorphism?

Question 39

What are some types of ore deposits that have formed in association with contact metamorphism?

Question 40

What is an isograd?

Question 41

The pressure exerted on rocks by the weight of overlying rocks is called ____________________ pressure. With this type of pressure, the stress on the rock is the ____________________ in all directions.

Question 42

____________________ and ____________________ are two different types of pressures to which rocks can be subjected that can cause metamorphism.

Question 43

Metamorphism is most common along ____________________ plate boundaries.

Question 44

A foliation found in metamorphic rocks with more than 50% plate and elongated minerals is known as ____________________, and the rock this foliation is found in is called ____________________.

Question 45

Metamorphism at an oceanic-continental convergent plate boundary where temperatures are low and pressures are high results in rocks typical of the ____________________ facies.

Question 46

The type of metamorphism that occurs over large areas, commonly at convergent plate margins, and is responsible for the production of most metamorphic rocks is ____________________.

Question 47

If a rock is exposed to such high temperatures that it melts, it forms a(n) ____________________ and becomes a(n) ____________________ rock.

Question 48

The three types of metamorphism are ____________________, ____________________, and ____________________.

Question 49

The most important fluid promoting metamorphism is ____________________.

Question 50

What is the parent rock for the following metamorphic rocks: marble: ____________________; anthracite: ____________________; quartzite: ____________________; slate: ____________________; schist: ____________________; and greenstone: ____________________.

Question 51

Metamorphic rocks are commonly divided into these two groups, based on their textures: ____________________ and ____________________.

Question 52

A rock with both igneous and high-grade metamorphic characteristics is a(n) ____________________.

Question 53

One plate tectonic process that causes very widespread metamorphism is ____________________.

Question 54

Many ore deposits, including tin and tungsten, are associated with ____________________ metamorphism.

Question 55

In schist with a rotated garnet crystal, geologists know that ____________________ pressure was unequally applied during metamorphism.

Question 56

As the plate subducts until it begins to melt, it forms ____________________, which rises and results in ____________________ metamorphism.

Question 57

The type of metamorphism that typically produces the hard, dense, fine-grained rocks called mylonites is called ____________________.

Question 58

Sillimanite is a(n) ____________________-temperature, ____________________-grade metamorphic mineral.

Question 59

A rock with segregated light and dark bands, containing the minerals quartz, feldspar, hornblende, and mica, is a(n) ____________________ gneiss.

Question 60

If metamorphic rock contains biotite, garnet, and staurolite, it is ____________________ grade.

Question 61

The intensity of regional metamorphism may be recognized by:

A) index of recrystallization.
B) index fossils.
C) index minerals.
D) index polymorphs.
E) index cards.

Question 62

The type of metamorphism that is common in fault zones, in which rocks are subjected to high differential pressures, is called:

A) contact.
B) regional.
C) differential metamorphism.
D) dynamic metamorphism.
E) hydrothermal.

Question 63

Which three processes bring about metamorphism?

A) heat, pressure, weathering
B) melting, pressure, fluid activity
C) fluid activity, heat, melting
D) pressure, fluid activity, heat
E) crystallization, differential pressure, melting

Question 64

The reaction of country rock with solutions from a cooling magma is known as:

A) hydrothermal solution.
B) hydroxide alteration.
C) geothermal alteration.
D) hydrothermal alteration.
E) hydrostatic alteration.

Question 65

Which of the following lists of foliated rock types is arranged according to increasing coarseness of texture, also going from low-grade to high-grade metamorphism?

A) slate, phyllite, gneiss, schist
B) slate, amphibolite, schist, phyllite
C) schist, phyllite, gneiss, slate
D) slate, phyllite, schist, gneiss
E) schist, phyllite, amphibolite, gneiss

Question 66

Metamorphic rocks are the oldest known rocks.

Question 67

Metamorphic rocks can indicate the physical conditions that once existed in a geological setting.

Question 68

The two most important sources of heat for metamorphism are:

A) intrusive magma bodies and deep burial.
B) intrusive magma bodies and heat from the core.
C) deep burial and volcanism.
D) radioactive decay and volcanism.
E) radioactive decay and deep burial.

Question 69

Metamorphism takes place:

A) in the liquid state, melted by contact with magma.
B) in the solid state, with or without fluid activity.
C) only at great depth.
D) in the liquid state, melted by contact with magma, and only at great depth.
E) in the liquid state, melted by contact with magma; in the solid state, with or without fluid activity, AND only at great depth.

Question 70

Which of the following correctly lists metamorphic mineral assemblages in order of decreasing temperature/pressure of formation?

A) chlorite, biotite, garnet, staurolite, kyanite, sillimanite
B) biotite, garnet, chlorite, staurolite, sillimanite, kyanite
C) garnet, biotite, chlorite, sillimanite, staurolite, kyanite
D) sillimanite, staurolite, kyanite, garnet, biotite, chlorite
E) sillimanite, kyanite, staurolite, garnet, biotite, chlorite

Question 71

Foliated metamorphic rocks form when pressure is applied:

A) outward at the two sides (tension).
B) inward at the two sides (compression).
C) in a shearing environment (tension).
D) as compression or tension.

Question 72

In adjacent rocks that show a gradual increase in metamorphic intensity, the first appearance of a particular index mineral indicates

A) the location of the minimum pressure and temperature conditions needed for the formation of that mineral.
B) the location of the maximum pressure and temperature conditions needed for the formation of that mineral.
C) the rocks formed under the same broad conditions of temperature and pressure.
D) the location on Bowen's reaction series where that mineral is in equilibrium.

Question 73

An example of a region where mylonites are formed is the:

A) Cascade Range.
B) mid-oceanic ridges.
C) San Andreas Fault Zone.
D) Valles Marianas Rift Zone.
E) Mendocino Fracture Zone.

Question 74

Metamorphism is a physical and chemical change that occurs in such a way that:

A) disequilibrium is reached with the new physical and chemical environment.
B) a dynamic equilibrium is reached.
C) equilibrium with the new environment is disturbed.
D) the rock reaches equilibrium with its new environment.
E) the rock's chemistry and texture become increasingly unstable.

Question 75

Metamorphic rocks are very common in the crystalline basement rocks of the oldest parts of continents.

Question 76

A regional metamorphic rock that has both igneous and high-grade metamorphic characteristics is a(n):

A) schist.
B) amphibolite.
C) migmatite.
D) granitite.

Question 77

Metamorphic rocks indicate that an even older parent rock once existed in that place.

Question 78

Metamorphic rocks may form from:

A) igneous rocks.
B) sedimentary rocks.
C) other metamorphic rocks.
D) both igneous and sedimentary rocks.
E) igneous, sedimentary, or metamorphic rocks.

Question 79

Divergent plate boundaries are characterized by:

A) hydrothermal alteration and contact metamorphism.
B) regional and contact metamorphism.
C) regional and dynamic metamorphism.
D) dynamic and contact metamorphism.
E) hydrothermal alteration and dynamic metamorphism.

Question 80

Metamorphic rocks can represent the chemical changes that have occurred at various depths.