Deck 7: Metamorphism: a Process of Change

Question 1

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

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

Answer 1

C

Question 2

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.

Answer 2

C

Question 3

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

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

Answer 3

C

Question 4

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

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

Question 5

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) volcanic

Question 6

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 7

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

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

Question 8

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 9

Spreading peanut butter on bread is an application of

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

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

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

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

Question 13

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 14

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 15

During metamorphism,small mineral grains can reform into larger,interlocking grains of the same mineral.This process is called _________.

A) foliation
B) elongation
C) pressure solution
D) recrystallization

Question 16

During metamorphism,new mineral grains can form that are not found in the protolith.This process is called _________.

A) foliation
B) elongation
C) pressure solution
D) neocrystallization

Question 17

The figure below shows the application of

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

Question 18

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.

Question 19

When actions that squeeze or push on a rock are stronger in some directions than others,we call this

A) differential stress.
B) pressure.
C) shear stress.
D) weathering.

Question 20

The gain and loss of chemical elements in a metamorphic rock induced by a reaction with hot groundwater is termed

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

Question 21

Marble and quartzite are non-foliated 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 22

The transformation of protoliths into metamorphic rocks solely through transfer of heat is termed ________ metamorphism.

A) regional
B) thermal
C) shock
D) dynamic

Question 23

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 24

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

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

Question 25

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

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

Question 26

Hornfels facies rocks form in shallow crustal environments due to contact (thermal)metamorphism.As a result,hornfels typically

A) are foliated.
B) form at high pressures and low temperatures.
C) form at low pressures and high temperatures.
D) are associated with deep sedimentary basins.

Question 27

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 28

Metamorphism caused by shear stress that does not require changes in temperature or pressure results in a rock known as _________.

A) slate
B) gneiss
C) breccia
D) mylonite

Question 29

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 30

Thermal (contact)metamorphism produces

A) foliated rocks only.
B) non-foliated rocks only.
C) both foliated and non-foliated rocks.
D) thermal metamorphism does not produce any metamorphic rocks.

Question 31

Mylonites,formed from dynamic metamorphism,typically occur where there has been substantial

A) high temperature.
B) high pressure.
C) hydrothermal fluid movement.
D) shearing.

Question 32

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 33

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 34

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 35

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 36

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 37

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 38

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 39

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 40

What is a contact aureole?

A) a location where two different types of metamorphic rock are next to each other
B) a type of foliation that develops due to shear stress
C) the belt of metamorphosed rocks surrounding an igneous intrusion
D) the location where a protolith transitions to metamorphic rock

Question 41

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 non-foliated metamorphic rocks are likely to be found.
D) it is possible to find a variety of metamorphic rocks including high-,intermediate-,and low-grade rocks.

Question 42

Examine the photomicrograph of a metamorphic rock below.Label the direction of the greatest compressive stress and the direction of preferred mineral orientation that created the foliation in the rock.

Question 43

________ 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 44

The presence of metamorphic rocks exposed today at the Earth's surface tells us that _______ has occurred.

A) subduction
B) metasomatism
C) foliation
D) erosion

Question 45

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 46

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

Question 47

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 48

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 49

What is slaty cleavage and how does it form? Contrast the form of bedding planes in slate's protolith versus cleavage planes in a slate.

Question 50

Rocks resulting from shock metamorphism are likely to reveal minerals that underwent _______.

A) plastic deformation
B) hydrothermal alteration
C) a phase change
D) recrystallization

Question 51

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 52

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

Question 53

Precambrian metamorphic rocks are exposed at the surface

A) on Mars and Venus but not on the 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 54

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.Starting from the protolith,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,migmatite,phyllite,schist,shale,and slate.

Question 55

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 56

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 57

What distinguishes metamorphic grade from metamorphic facies?

Question 58

Describe the similarities and differences between schist and phyllite.

Question 59

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 60

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