Deck 7: Metamorphism and Metamorphic Rocks

Question 1

Which of the following best describes the conditions of contact metamorphism?

A)Pressures are very high, the rock is deeply buried, and temperatures are raised gradually by Earth's internally generated heat.
B)Pressures are fairly low, the rock is in the upper part of the crust, the heat for baking the neighbouring rocks is supplied quickly from the intrusion of a nearby magma body.
C)Heat is generated very quickly by shearing and mechanical movements along faults.
D)Depths are so deep and temperatures are so high that the rocks begin to partially melt.

Answer 1

B

Question 2

How would you correctly refer to the metamorphic grade of a rock that contains bundles of fibrous sillimanite along with pyroxene and sanidine as its highest temperature minerals such as a coarse grained granulite facies gneiss?

A)"S grade"
B)high grade > 600° C
C)intermediate grade
D)low grade < 200° C

Answer 2

B

Question 3

Where would you expect to find chlorite and zeolites filling up voids and fractures in relatively undeformed rocks?

A)burial metamorphism of sedimentary or volcanic rocks
B)intermediate grade metamorphism of limestones
C)high grade metamorphism of layered sandstones and shales
D)high temperature hornfels contact metamorphism of salts and rock gypsum

Answer 3

A

Question 4

A massive mudstone metamorphosed to biotite hornfels facies would have ________.

A)biotite defining wavy parallel foliations throughout the rock
B)breccia of angular biotite clasts crushed and sheared out of shape
C)irregular spots of randomly oriented biotite platelets called porphyroblasts
D)remnants of biotite, now mostly recrystallized to garnet in discreet layers

Question 5

A sillimanite hornfels would ________.

A)be formed at the highest grade of regional metamorphism
B)lie on the outermost edge of a contact aureole where hornfels are preserved
C)lie entirely within the core of the contact aureole occupied by the high grade
D)usually form from the complete subduction of ocean crust deep into the mantle

Question 6

________ is a nonfoliated rock formed by the contact metamorphism of fine grained rocks like shales, mudstones, or volcanics.

A)Schist
B)Marble
C)Gneiss
D)Hornfels

Question 7

How would you correctly refer to the metamorphic grade of a rock that contains abundant chlorite as its highest temperature mineral such as a greenschist or phyllite?

A)"C grade"
B)high grade > 600° C
C)intermediate grade
D)low grade < 200° C

Question 8

Under the application of uniform, confining pressure, rocks will generally ________.

A)bend, fold, buckle, and shear to make typical deformed metamorphic textures
B)grow or crystallize a new set of low density hydrous minerals
C)increase in density but retain primary bedding orientations
D)shatter and turn into a breccia

Question 9

What type of environment is typified by brittle deformation?

A)deep burial with great confining pressure
B)intermediate depths with long slow heating and gradual strain rates
C)shallow, low temperature settings with high strain rates
D)shallow very high temperature settings as in contact metamorphism

Question 10

About 1.2 to 1.0 billion years ago, Canada had a mountain range the size of the modern Himalayas, with high grade metamorphic rocks (>800° C)forming in its roots.Where was this located?

A)The Coast Mountains of B.C.
B)The Canadian Rockies
C)The Grenville Orogen stretching between Georgian Bay Ontario and Newfoundland
D)The Trans Hudson Orogen of Saskatchewan and Manitoba

Question 11

Metamorphic grade refers to ________.

A)economic value of metamorphic rocks
B)how much we'll have to curve your test mark if you are guessing!
C)metamorphic intensity as recorded by particular minerals which are sensitive to temperature and pressure
D)recrystallization versus amount of primary mineral grains

Question 12

Where and how does metamorphism occur?

A)mainly at low temperatures in the roots of volcanic mountain belts
B)beneath the thick accumulations of in sedimentary basins
C)wherever solid rocks are subjected to new conditions of temperature, pressure, stress, and a change in their constituent fluids
D)in response to sudden catastrophic geologic changes, mostly in the Precambrian.

Question 13

A large block of sedimentary rock that has fallen into the top of a magma chamber and become metamorphosed is called ________.

A)an astrobleme
B)an inverted aureole
C)an amphibolite boudin
D)a roof pendant

Question 14

________ is a strong, parallel alignment of coarse mica flakes and/or of different mineral bands in a metamorphic rock.

A)Rock cleavage
B)Foliation
C)Brecciation
D)Shear stress

Question 15

What term describes the zone of contact metamorphism where hornfels forms, surrounding an intrusive magma body?

A)astrobleme
B)hydrothermal vein
C)oracle
D)aureole

Question 16

During metamorphism, what is the major effect of chemically active fluids?

A)increase the pressures in deeply buried, regional-metamorphic zones
B)aid in the movement of dissolved ions and silicate constituents from parent minerals and facilitate growth of new metamorphic mineral grains
C)prevent partial melting so solid rocks can undergo very high temperature regional metamorphism
D)facilitate the formation of schistosity and gneissic banding in hornfels and skarns

Question 17

Which two metamorphic rocks are each composed predominantly of a single mineral?

A)mica schist and granitic gneiss
B)fault breccia and graphitic schist
C)garnet schist and andalusite hornfels
D)marble and quartzite

Question 18

What is the major source of heat for contact metamorphism?

A)deep burial and heat from Earth's interior
B)heat from grinding and shearing on faults
C)heat from the spontaneous decomposition of micas and feldspars
D)heat from a nearby magma body

Question 19

Which rock forms by contact metamorphism of fine grained mudstones, shales, and volcanics?

A)hornfels
B)limestone
C)gneiss
D)phyllite

Question 20

Chemically active fluids like ________ tend to transport ions and mineral components and their activity ________ with increasing temperature.

A)petroleum hydrocarbons, increases
B)HCl and hydrogen sulphide, ceases
C)carbon dioxide, decreases
D)water, increases

Question 21

What texture results from the alignment of abundant, coarse-grained, mica flakes in a medium grade regional metamorphic rock?

A)schistosity
B)gneissic banding
C)slaty cleavage
D)shatter cones

Question 22

________ is typically formed by metamorphism of a mature sandstone.

A)marble
B)slate
C)amphibolite
D)quartzite

Question 23

Which is a foliated, fine-grained regional metamorphic rock formed from mudstone and shale?

A)phyllite
B)hornfels
C)gneiss
D)marble

Question 24

Which regional metamorphic rock type listed below represents the highest grade?

A)hornfels
B)mica schist
C)slate
D)phyllite

Question 25

What do you call a coarse grained, foliated metamorphic rock having thick bands of dark ferromagnesian minerals alternating with pink feldspar and quartz layers?

A)hornfels
B)phyllite
C)gneiss
D)schist

Question 26

Which of the following forms at a medium grade of regional metamorphism?

A)hornfels
B)schist
C)slate
D)phyllite

Question 27

Which is a nonfoliated metamorphic rock consisting mostly of calcite?

A)marble
B)hornfels
C)gneiss
D)phyllite

Question 28

In which setting would regional metamorphism most likely occur?

A)at shallow depths below an oceanic ridge or rift zone
B)at shallow depths along major transform faults on the continental crust
C)at great depths in the crust where two continents are colliding
D)on the rims of large meteorite impact craters

Question 29

What foliated, regional metamorphic rock is texturally intermediate between slate and schist?

A)fault breccia
B)phyllite
C)quartzite
D)gneiss

Question 30

________ forms from the metamorphism of limestone or dolostone.

A)Migmatite
B)Amphibolite
C)Marble
D)Quartzite

Question 31

Which one of the following statements is false?

A)Slate forms from shale and mudstones.
B)Slate has abundant, coarse-grained mica.
C)In slate, rock cleavage is common.
D)In slate, sedimentary features may be visible.

Question 32

Which is a coarse-grained, high-grade, metamorphic rock with alternating bands or stringers of light and dark minerals?

A)gneiss
B)hornfels
C)marble
D)phyllite

Question 33

What major change occurs during metamorphism of limestone to marble?

A)Calcite grains grow larger and increase in size.
B)Clays crystallize to micas, forming a highly foliated, mica-rich rock.
C)Limestone grains react to form quartz and feldspars.
D)Calcite grains are dissolved away leaving only marble crystals.

Question 34

Graphite is identified in a particular schist.Which one of the following conclusions is justified?

A)The rock also contains diamonds; both are crystalline forms of the element carbon.
B)The schist formed from a quartz-rich, sedimentary limestone.
C)The graphite lubricated shearing movements along a fault, causing a schist to form.
D)The pre-metamorphic rock was a shale or mudstone containing organic matter.

Question 35

Increasing regional metamorphic grade of a shale or mudstone would produce the sequence ________.

A)breccia, gouge, mylonite, ultramylonite
B)hornfels, amphibolite, migmatite
C)greenschist, amphibolite, granulite
D)slate, phyllite, schist, gneiss

Question 36

Which low-grade metamorphic rock, composed of extremely fine mica and other mineral grains, typically exhibits well-developed rock cleavage?

A)schist
B)hornfels
C)quartzite
D)slate

Question 37

The intensity and grade of ________ metamorphism is most intense where ________.

A)burial (zeolite facies), the soil horizon gives way to unaltered bedrock
B)cataclastic (dynamic), muds are shattered by raindrop impacts
C)contact, clays are recrystallized and reacted entirely to chlorite
D)regional, continents collide forming a mountain belt

Question 38

What platy, parallel, mineral grains are the most visual aspect of foliated metamorphic rocks?

A)micas
B)feldspars
C)carbonates
D)quartz

Question 39

________ is characterized by the segregation of light- and dark-coloured minerals into thin layers or bands.

A)Garnet hornfels
B)Granite gneiss
C)Slate
D)Quartzite

Question 40

Which of the following lists the rocks in the order of increasing grain size and increasing grade for regionally metamorphosed mud rocks?

A)phyllite, slate, schist
B)schist, slate, phyllite
C)slate, phyllite, schist
D)slate, schist, phyllite

Question 41

Which facies would you expect to find with the development of glaucophane at high pressure?

A)blueschist
B)amphibolite
C)granulite
D)hornfels

Question 42

What are tekites?

A)hard, foliated, hornfels chips in a shale heated by an intrusive granite
B)unusually coarse-grained migmatites that crystallized in a caldera
C)globular to teardrop-shaped, dark, glassy, silica-rich impact melts
D)granular breccias produced by fault zone shattering

Question 43

Increasing regional metamorphism of a basalt or gabbro would produce the sequence ________.

A)breccia, gouge, mylonite, ultramylonite
B)hornfels, amphibolite, migmatite
C)greenschist, amphibolite, granulite
D)slate, phyllite, schist, gneiss

Question 44

Why is the regional metamorphism of ocean crust in a subduction zone considered separately from regular regional metamorphism?

A)The ocean crust has no hydrous minerals to destroy or recrystallize.
B)Both the basaltic composition and very low geothermal gradient (Low T, Hi P)are unique and lead to different facies than seen in continental rocks.
C)Unlike regular regional metamorphism, this does not occur along plate margins.
D)Because this setting does not involve any strain deformation.

Question 45

A ________ forms at very high pressures but relatively low temperatures associated with subduction of oceanic crust and sediments.

A)mylonite
B)migmatite
C)sillimanite bearing marble
D)blueschist

Question 46

Tektites originate in what metamorphic environment?

A)low pressure and high temperature associated with volcanism
B)high temperature melting associated with meteorite impacts
C)very high pressures and temperatures associated with deep subduction
D)high temperatures and shearing stresses in an oceanic transform fault

Question 47

What is the end product (highest grade)reached by subduction zone metamorphism of basalt?

A)gabbro pegmatite
B)granulite
C)gneiss
D)eclogite

Question 48

Which facies would you expect to find with intermediate temperature-pressure regional metamorphism?

A)amphibolite
B)granulite
C)blueshist
D)hornfels

Question 49

In 1915, which geologist proposed a series of metamorphic facies to describe the progressive mineralogic and textural changes in basalt as a function of temperature and pressure?

A)Norman Bowen
B)George Dawson
C)Pennti Eskola
D)William Logan

Question 50

Which one of the following is not genetically associated with the terrestrial impact of an asteroid or large meteorite?

A)tekites
B)blueschists
C)impact crater
D)shatter cones

Question 51

Long linear metamorphic fold belts mark ________.

A)modern or former convergent continental margins
B)the youngest mountains with the slowest rates of uplift
C)divergent plate settings (rifts)
D)zones with the lowest geothermal gradients

Question 52

Which of the following rocks would exhibit visible, textural evidence of having undergone significant partial melting?

A)marbles
B)migmatites
C)porphyroblastic hornfels
D)coarse grained angular fault breccias

Question 53

Amphibolite is a foliated metamorphic rock composed principally of hornblende and plagioclase.How does it form?

A)by contact metamorphism of quartzose sandstone cut by a granitic batholith
B)by regional metamorphism of volcanic rocks such as andesite and basalt
C)by gouging and crushing of limestone along a fault
D)by the impact of an asteroid on interbedded sandstone and shale

Question 54

In the formation of migmatites, which minerals start to melt first?

A)amphibole, biotite, and garnet
B)quartz and feldspar
C)chlorite and calcite
D)zircon and magnetite

Question 55

Which facies would you expect to find with hydrous low temperature-low pressure burial metamorphism?

A)zeolite
B)amphibolite
C)granulite
D)blueschist

Question 56

________ is thought to form by partial melting and in situ crystallization of the melted portion at the highest grade of regional metamorphism of crustal rocks.

A)Magmatite
B)Magnetite
C)Migmatite
D)Meltite

Question 57

Which facies would you expect to find with high temperature-low pressure contact metamorphism?

A)hornfels
B)amphibolite
C)granulite
D)blueschist

Question 58

________ contain the oldest dated metamorphic rocks in Canada.

A)The Acasta Gneiss, Northwest Territories
B)The Grenville Province
C)The Nuwuagittuq Greenstone, Quebec
D)The Ungava Orogen

Question 59

A ________ forms at very high pressures but moderately low temperatures associated with subduction of oceanic crust and sediments.

A)mylonite
B)migmatite
C)biotite marble
D)blueschist

Question 60

________ are formed from the impact of an asteroid or meteorite.

A)Astroblemes
B)Subduction zones
C)Volcanoes
D)Batholiths

Question 61

Contact metamorphism is most readily apparent at shallow depths, where the thermal gradients are the steepest (hot intrusion/cold roof rock).

Question 62

High-grade, regional metamorphism produces significant and recognizable changes in the textures and mineral compositions of rocks.

Question 63

At elevated pressures, water can be used to supply unequal, directed pressure by hydraulic forces.

Question 64

Calcite is the main mineral constituent of the sedimentary rock limestone and of the metamorphic rock marble.

Question 65

Three major factors involved in metamorphism are elevated temperature, elevated pressure, and the chemical action of hot fluids.

Question 66

Match the rock with the appropriate description.
A.hornfels B.marble C.gneiss D.phyllite
________ foliated, fine-grained metamorphic rock formed from mudstone and shale

Question 67

Uniform high pressure metamorphism of a quartz-rich sediment will generate a foliated rock like slate, phyllite, or schist.

Question 68

The type of metamorphic rock that is formed depends on the pressure, temperature, stress rate, fluids, and original parent rock composition.

Question 69

Match the rock with the appropriate description.
A.hornfels B.marble C.gneiss D.phyllite
________ forms by contact metamorphism of mudstones and shales

Question 70

Most metamorphism happens entirely in the solid state.

Question 71

Hornfels are metamorphic rocks produced at great depths and high temperatures associated with regional metamorphism.

Question 72

At high pressures and elevated temperatures of regional metamorphism, silicate rocks are more resistant to flowage and deformation than at low temperatures and pressures.

Question 73

Muscovite is a hydrous sheet silicate typical of low metamorphic grades.

Question 74

Match the rock with the appropriate description.
A.hornfels B.marble C.gneiss D.phyllite
________ coarse-grained, metamorphic rock with alternating bands or stringers of light and dark minerals

Question 75

Match the rock with the appropriate description.
A.hornfels B.marble C.gneiss D.phyllite
________ nonfoliated metamorphic rock consisting mostly of calcite

Question 76

Foliated metamorphic rocks are composed largely of nonequidimensional grains of minerals such as quartz and calcite.

Question 77

During metamorphism, most rock is composed of solid mineral grains, but small amounts of hot fluids or partial melting may facilitate the metamorphic process.

Question 78

Ductile deformation occurs at low stress rates.

Question 79

Quartzites and metaconglomerates are usually formed along faults by intensive fracturing and fragmentation of conglomerate beds and quartz veins.

Question 80

Chlorite hornfels would likely be restricted to the edge of the metamorphic aureole.