Deck 8: Metamorphism: a Process of Change

Question 1

Spreading peanut butter on bread is an application of

A) normal stress.
B) pressure.
C) shear stress.
D) metasomatism.

Answer 1

C

Question 2

The net chemical change in a metamorphic rock induced by a reaction with hot groundwater is termed

A) foliation.
B) metasomatism.
C) anachronism.
D) hydrosomatism.

Answer 2

B

Question 3

Clay minerals within a buried body of slate are recrystallized at high temperatures and pressures to form mica,producing a rock called phyllite.This is an example of

A) diagenesis.
B) erosion.
C) metamorphism.
D) weathering.

Answer 3

C

Question 4

Which of the following processes are NOT involved in metamorphism?

A) contact with a hot pluton
B) contact with hydrothermal fluids
C) heat and pressure associated with deep burial
D) cementation and compaction of grains during diagenesis

Question 5

The application of ________ during metamorphism causes elongated crystals to align parallel with each other.When this happens,the rock develops ________.

A) pressure; a homogeneous texture
B) differential stress; foliation
C) high temperatures; foliation
D) pressure; foliation

Question 6

________ commonly serves as a protolith in the formation of marble.

A) Limestone
B) Sandstone
C) Shale
D) Gneiss

Question 7

Broadly,metamorphism involves

A) the settling of crystals in a melt as it cools.
B) the sorting of grains by size,as accomplished by rivers and beach waves.
C) the cementation of loose grains and the precipitation of new minerals into pore spaces.
D) changes in mineralogy and texture in response to heat and stress.

Question 8

A heavy book is placed on top of a ball of pizza dough,causing the dough to flatten.This is an application of

A) normal stress.
B) pressure.
C) shear stress.
D) metasomatism.

Question 9

Which of the following processes does NOT occur in the formation of metamorphic rock?

A) the realignment of minerals so that they develop a preferred orientation
B) the segregation of minerals into layers of different compositions
C) the solid-state rearrangement of atoms or ions to create a new assemblage of minerals
D) complete remelting of the rock,followed by solidification to form a new rock

Question 10

________ commonly serves as a protolith in the formation of quartzite.

A) Limestone
B) Sandstone
C) Shale
D) Slate

Question 11

Differential stress will cause crystals to align in a preferred orientation unless the crystals are

A) primarily mica.
B) platy.
C) equant.
D) elongate.

Question 12

The figure below shows the application of

A) tension.
B) pressure.
C) normal stress.
D) shear stress.

Question 13

Consult the figure below.Compared with amphibolite metamorphic facies,greenschist facies

A) consist of lower-grade rocks.
B) consist of higher-grade rocks.
C) involve partially melted rocks.
D) have the same grade but a different chemistry due to different protoliths.

Question 14

________ commonly serves as a protolith in the formation of phyllite.

A) Limestone
B) Sandstone
C) Shale
D) Basalt

Question 15

A protolith

A) is always metamorphic rock.
B) is always igneous rock.
C) is always sedimentary rock.
D) may belong to any of the three primary rock types.

Question 16

In the formation of gneiss from a granite protolith,distinctive compositional bands form because of

A) crystals migrating within the rock.
B) crystals dissolving,with atoms and ions migrating and reorganizing as new crystals.
C) crystals melting,with new crystals solidifying in color bands.
D) chemical reactions with groundwater.

Question 17

The preexisting rock that is subsequently altered to form a metamorphic rock is termed a

A) xenolith.
B) source rock.
C) protolith.
D) phenocryst.

Question 18

A body of gneiss is subjected to heat and forms a melt.Later,the melt cools and crystallizes to form a (n)________ rock.

A) metamorphic
B) igneous
C) sedimentary
D) metaigneous

Question 19

________ commonly serves as a protolith in the formation of slate.

A) Limestone
B) Sandstone
C) Shale
D) Basalt

Question 20

A buried body of shale is subjected to differential stress,causing clay minerals to realign and produce slate.This is an example of

A) diagenesis.
B) erosion.
C) metamorphism.
D) weathering.

Question 21

Consult the figure below.Compared with low-grade metamorphic rocks,high-grade rocks

A) always contain more quartz and feldspar.
B) are produced closer to the surface.
C) are produced at greater temperatures and pressures.
D) are produced at cooler temperatures but greater pressures.

Question 22

Mylonites,formed from dynamic metamorphism,typically do NOT display

A) foliation roughly parallel to a fault.
B) very fine grains.
C) shear zones.
D) bands of randomly oriented mica grains.

Question 23

Foliated metamorphic rocks possess

A) leafy plant fossils (ancient foliage).
B) a homogeneous texture resulting from randomly oriented grains.
C) mineral grains in preferred orientations or patterns of association.
D) minerals precipitated directly from seawater.

Question 24

The transformation of low-grade metamorphic rocks into high-grade metamorphic rocks is termed ________ metamorphism.

A) foliated
B) prograde
C) retrograde
D) dynamic

Question 25

The blueschist facies form under which of these conditions:

A) high temperature and high pressure
B) low temperature and low pressure
C) high temperature but relatively low pressure
D) high pressure but relatively low temperature

Question 26

A preferred orientation of large,flaky mica crystals within metamorphic rock is termed

A) slaty cleavage.
B) phyllitic luster.
C) schistosity.
D) compositional banding.

Question 27

Two common metamorphic rocks that typically lack foliation are ________ and ________.

A) slate; phyllite
B) gneiss; migmatite
C) quartzite; marble
D) schist; metaconglomerate

Question 28

The rapid,deep burial of sediments in an accretionary prism leads to the formation of a metamorphic rock termed

A) blueschist.
B) greenschist.
C) migmatite.
D) gneiss.

Question 29

Consult the figure below.The region of thermally metamorphosed rock surrounding a cooled pluton is called a (n)

A) shear zone.
B) aureole.
C) oriole.
D) metamorphic ring.

Question 30

Which of the following statements is false? Hornfels facies rocks

A) are typically nonfoliated.
B) form at high pressures and low temperatures.
C) often form as a result of contact metamorphism.
D) are often associated with igneous intrusions

Question 31

Which list properly orders foliated metamorphic rocks from lowest to highest grade from left to right?

A) conglomerate,sandstone,siltstone,and shale
B) shale,slate,phyllite,and quartzite
C) slate,phyllite,schist,and gneiss
D) gneiss,phyllite,schist,and slate

Question 32

Retrograde metamorphism will not occur unless an increased amount of ________ is added to the system.

A) temperature
B) differential stress
C) pressure
D) water

Question 33

A mineral within a metamorphic rock that can be used to narrowly constrain the temperature and pressure of rock formation is termed a (n)________ mineral.

A) thermal
B) index
C) mafic
D) halide

Question 34

Which of the following describes the progression of rock types through increasing metamorphic grade from left to right?

A) shale $\rightarrow$ slate $\rightarrow$ phyllite $\rightarrow$ schist
B) basalt $\rightarrow$ andesite $\rightarrow$ rhyolite $\rightarrow$ granite
C) sandstone $\rightarrow$ gneiss $\rightarrow$ hornfels $\rightarrow$ zeolite
D) migmatite $\rightarrow$ slate $\rightarrow$ eclogite $\rightarrow$ schist

Question 35

Marble and quartzite are nonfoliated metamorphic rocks because

A) they are never found beneath fault zones or collisional mountain ranges.
B) both are dominated by minerals that produce equant grains.
C) both are dominated by minerals with crystalline structures that cannot be dissolved.
D) dynamothermal metamorphism can break down the structures of their constituent minerals,but the minerals are unstable in that metamorphic environment.

Question 36

The transformation of high-grade metamorphic rocks into low-grade metamorphic rocks is termed ________ metamorphism.

A) foliated
B) prograde
C) retrograde
D) dynamic

Question 37

Slaty cleavage,schistosity,and compositional banding are all examples of

A) mineral cleavage.
B) foliation.
C) recrystallization.
D) metamorphic facies.

Question 38

Which of the following is a primary difference between phyllite and schist?

A) Schist contains mica,whereas phyllite contains only clay.
B) Phyllite contains mica,whereas schist contains only clay.
C) Mica crystals within schist are larger than those within phyllite.
D) Mica crystals within phyllite are larger than those within schist.

Question 39

The mineral assemblage within metamorphic rock is

A) always identical to that found within its protolith.
B) dependent only on the mineral assemblage of its protolith.
C) dependent only on the temperature and pressure of formation.
D) dependent on both the mineral assemblage of its protolith and the temperature and pressure of formation.

Question 40

Thermal (contact)metamorphism produces

A) foliated rocks only.
B) nonfoliated rocks only.
C) both foliated and nonfoliated rocks.
D) Thermal metamorphism does not produce any metamorphic rocks.

Question 41

Precambrian metamorphic rocks are exposed at the surface

A) on Mars and Venus but not on Earth.
B) at places in continental interiors (called platforms).
C) at places in continental interiors (called shields).
D) at the bottom of the deep sea.

Question 42

What is a metamorphic aureole? What is the relationship between grade of metamorphism and proximity to the intrusion? What types of conditions are responsible for the formation of an aureole?

Question 43

Thermal (contact)metamorphism occurs

A) in areas surrounding igneous intrusions.
B) only where gneiss sits in contact with schist.
C) as a consequence of the sinking of a broad region to great depth.
D) only at the surface,where rock is in contact with the atmosphere.

Question 44

Draw the orientation of the preferential stress that created the foliation in the figure below.

Question 45

During dynamothermal (regional)metamorphism,several metamorphic processes are at work.Describe these processes and the effects they might have on rocks subjected to this type of metamorphism.

Question 46

What metamorphic facies would most commonly be associated with a subduction zone and why?

Question 47

________ metamorphism affects the greatest volumes of rock and produces the greatest variety in metamorphic rock types.

A) Thermal
B) Regional
C) Dynamic
D) Shock

Question 48

Potassium feldspar reacts with water to form clay.This is an example of

A) diagenesis.
B) erosion.
C) metamorphism.
D) weathering.

Question 49

Describe the similarities and differences between schist and phyllite.

Question 50

Metamorphic grade describes the intensity or degree of metamorphism.The metamorphic grade of a rock is determined mainly by the temperature and amount of recrystallization or neocrystallization to which a rock is subjected.List the following rocks in order from low-grade to high-grade metamorphic rocks,then describe the changes seen in the suite of rocks as the grade is increased: gneiss,slate,schist,phyllite,and migmatite.

Question 51

Rocks resulting from thermal (contact)metamorphism will NOT possess

A) a new mineral assemblage distinct from that found prior to intrusion.
B) larger crystals than those characterizing the country rock prior to intrusion.
C) foliation.
D) silicate minerals.

Question 52

What type of protolith would yield an amphibolite? What minerals are in the protolith and which ones form in the amphibolite?

Question 53

What is an index mineral? What do metamorphic isograds indicate? What is a metamorphic zone?

Question 54

Within a single mountain range,

A) only low-grade metamorphic rocks are likely to be found.
B) only high-grade metamorphic rocks are likely to be found.
C) only nonfoliated metamorphic rocks are likely to be found.
D) it is possible to find a variety of metamorphic rocks produced in distinct facies,including high-,intermediate-,and low-grade rocks.

Question 55

Consult the figure below.Hot water reacting with the crust is the basis for what type of metamorphism?

A) contact
B) hydrothermal
C) regional
D) shock

Question 56

Name the type of metamorphism that occurs next to an igneous intrusion.Describe the effects that this type of metamorphism has on the preexisting (country)rock surrounding the intrusion.

Question 57

Which of the following is NOT part of the process that leads to the exhumation of metamorphic rocks?

A) continents squeezing together
B) mountain belts collapsing
C) erosion
D) rising plumes of magma in the mantle

Question 58

Dynamothermal (regional)metamorphism occurs when

A) rock becomes deeply buried during continental collision and mountain building.
B) regression of the sea leads to erosion of sedimentary cover on a body of rock.
C) the upper surface of a body of rock develops a thick soil profile.
D) a pluton causes metamorphism in a small surrounding region.

Question 59

Regional metamorphism

A) takes place at low temperatures and low pressure.
B) takes place at low temperatures but high pressure.
C) is another name for thermal metamorphism.
D) is another name for dynamothermal metamorphism.

Question 60

Metamorphism includes a solid-state change in a rock caused by heat,pressure,and/or hydrothermal fluids.Explain what is meant by solid-state change.