Deck 7: Metamorphism and Metamorphic Rocks

Question 1

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

Answer 1

In some cases the original rock can be recognized because the changes are minor.Often the changes are so great that the original rock cannot be determined,since new minerals and/or a new texture may appear.

Question 2

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

Answer 2

Metamorphic rocks formed near Earth's surface along an oceanic-continental convergent plate boundary result from low-temperature,high-pressure conditions.As a subducted oceanic plate descends,it is subjected to increasingly higher temperatures and pressures that result in higher-grade metamorphism.

Question 3

Describe regional metamorphism.Where does it take place?

Answer 3

Regional metamorphism takes place over a large area and is caused by tremendous heat,pressure,and deformation in the deeper portions of the crust.The intensity of metamorphism varies from higher to lower,so a gradation in metamorphism is recognized in the resulting rocks.Regional metamorphism takes place along convergent plate boundaries during convergence and subduction.

Question 4

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

Question 5

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

Question 6

Describe the occurrence of metamorphism along a divergent plate boundary

Question 7

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

Question 8

What features would you look for to see if a metamorphic rock had undergone lithostatic or differential pressure?

Question 9

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

Question 10

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

Question 11

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

Question 12

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

Question 13

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

Question 14

What are index minerals,and what are they used for? Give an example of minerals that would be found in a low-grade,intermediate,and high-grade metamorphosed shale.

Question 15

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

Question 16

What is metamorphic grade,and present an example of how a rock reaches its metamorphic grade?

Question 17

Why is time important to metamorphic processes?

Question 18

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

Question 19

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

Question 20

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 21

Why is time important in metamorphism?

Question 22

What is the difference between slate and phyllite?

Question 23

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

Question 24

What causes dynamic metamorphism and where is it found?

Question 25

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

Question 26

What are some examples of nonfoliated metamorphic rocks?

Question 27

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

Question 28

How can fluid activity promote metamorphism?

Question 29

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 degrees C to 400 degrees C?

Question 30

What is a metamorphic zone?

Question 31

What is an isograd?

Question 32

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

Question 33

What is a metamorphic facies?

Question 34

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

Question 35

What is an aureole?

Question 36

What are some examples of foliated metamorphic rocks?

Question 37

What is lithostatic pressure?

Question 38

How are metamorphic facies defined or recognized?

Question 39

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 40

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 41

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

Question 42

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

Question 43

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

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

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

Question 46

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

Question 47

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 48

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

Question 49

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

Question 50

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

Question 51

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 52

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

Question 53

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

Question 54

The most important fluid promoting metamorphism is ____________________.

Question 55

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

Question 56

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

Question 57

Metamorphism is most common along ____________________ plate boundaries.

Question 58

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

Question 59

As the plate subducts until it begins to melt,it generates ____________________,which rises and causes ____________________ metamorphism.

Question 60

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

Question 61

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 62

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 63

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

Question 64

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

Question 65

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 66

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 67

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 68

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

Question 69

Metamorphic rocks are the oldest known rocks.

Question 70

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 71

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 72

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 73

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 74

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 75

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 76

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 77

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 78

Which of the following lists of foliated rock types is arranged according to increasing coarseness of texture?

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 79

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

Question 80

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

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