Ch.7 Metamorphism A Process of Change Test Bank Docx 6e - Geology Essentials 6e Complete Test Bank by Stephen Marshak. DOCX document preview.
CHAPTER 7: Metamorphism: A Process of Change
LEARNING OBJECTIVES
7A. Define metamorphism, and characterize the changes that a rock undergoes during the transformation of a protolith into a metamorphic rock.
7B. Explain the key processes that can take place during metamorphism.
7C. Contrast a metamorphic mineral assemblage with the assemblage of a protolith, and contrast a metamorphic texture with the texture of a protolith.
7D. Recognize the occurrence of foliation, and distinguish among different types of foliation.
7E. Identify and name examples of metamorphic rock, and explain how these rocks differ from one another.
7F. Relate kinds of metamorphism to various geologic settings in the context of plate tectonics theory.
7G. Describe how the character of a metamorphic rock reflects the grade of metamorphism, and how metamorphic grade depends on temperature and pressure.
MULTIPLE CHOICE
1. 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. |
2. The preexisting rock that is subsequently altered to form a metamorphic rock is termed a
a. | xenolith. | c. | protolith. |
b. | source rock. | d. | phenocryst. |
3. 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. |
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. |
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 | c. | sedimentary |
b. | igneous | d. | volcanic |
6. 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. | c. | metamorphism. |
b. | erosion. | d. | weathering. |
7. 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 |
8. 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. | c. | metamorphism. |
b. | erosion. | d. | weathering. |
9. 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 |
10. The gain and loss of chemical elements in a metamorphic rock induced by a reaction with hot groundwater is termed
a. | foliation. | c. | anachronism. |
b. | metasomatism. | d. | hydrosomatism. |
11. The figure below shows the application of
a. | tension. | c. | normal stress. |
b. | pressure. | d. | shear stress. |
12. Differential stress will cause crystals to align in a preferred orientation unless the crystals are
a. | primarily mica. | c. | equant. |
b. | platy. | d. | elongate. |
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. | c. | shear stress. |
b. | pressure. | d. | metasomatism. |
14. Spreading peanut butter on bread is an application of
a. | normal stress. | c. | shear stress. |
b. | pressure. | d. | metasomatism. |
15. When actions that squeeze or push on a rock are stronger in some directions than others, we call this
a. | differential stress. | c. | shear stress. |
b. | pressure. | d. | weathering. |
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. |
17. ________ commonly serves as a protolith in the formation of phyllite.
a. | Limestone | c. | Shale |
b. | Sandstone | d. | Basalt |
18. ________ commonly serves as a protolith in the formation of quartzite.
a. | Limestone | c. | Shale |
b. | Sandstone | d. | Slate |
19. ________ commonly serves as a protolith in the formation of slate.
a. | Limestone | c. | Shale |
b. | Sandstone | d. | Basalt |
20. ________ commonly serves as a protolith in the formation of marble.
a. | Limestone | c. | Shale |
b. | Sandstone | d. | Gneiss |
21. 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 | c. | high temperatures; foliation |
b. | differential stress; foliation | d. | pressure; foliation |
22. 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. |
23. Slaty cleavage, schistosity, and compositional banding are all examples of
a. | mineral cleavage. | c. | recrystallization. |
b. | foliation. | d. | metamorphic facies. |
24. A preferred orientation of large, flaky mica crystals within metamorphic rock is termed
a. | slaty cleavage. | c. | schistosity. |
b. | phyllitic luster. | d. | compositional banding. |
25. 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. |
26. 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. |
27. Two common metamorphic rocks that typically lack foliation are ________ and ________.
a. | slate; phyllite | c. | quartzite; marble |
b. | gneiss; migmatite | d. | schist; metaconglomerate |
28. 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. |
29. 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 |
30. Which of the following describes the progression of rock types through increasing metamorphic grade from left to right?
a. | shale slate phyllite schist |
b. | basalt andesite rhyolite granite |
c. | sandstone gneiss hornfels zeolite |
d. | migmatite slate eclogite schist |
31. 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 | c. | mafic |
b. | index | d. | halide |
32. The transformation of protoliths into metamorphic rocks solely through transfer of heat is termed ________ metamorphism.
a. | regional | c. | shock |
b. | thermal | d. | dynamic |
33. 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 |
34. Metamorphism caused by shear stress that does not require changes in temperature or pressure results in a rock known as _________.
a. | slate | c. | breccia |
b. | gneiss | d. | mylonite |
35. 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. |
36. 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 |
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. |
38. 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. |
39. The rapid, deep burial of sediments in an accretionary prism leads to the formation of a metamorphic rock termed
a. | blueschist. | c. | migmatite. |
b. | greenschist. | d. | gneiss. |
40. Mylonites, formed from dynamic metamorphism, typically occur where there has been substantial
a. | high temperature. |
b. | high pressure. |
c. | hydrothermal fluid movement. |
d. | shearing. |
41. Consult the figure below. The region of thermally metamorphosed rock surrounding a cooled pluton is called a(n)
a. | shear zone. | c. | oriole. |
b. | aureole. | d. | metamorphic ring. |
42. ________ metamorphism affects the greatest volumes of rock and produces the greatest variety in metamorphic rock types.
a. | Thermal | c. | Dynamic |
b. | Regional | d. | Shock |
43. 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. |
44. 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. |
45. 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. |
46. 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. |
47. Consult the figure below. Hot water reacting with the crust is the basis for what type of metamorphism?
a. | contact | c. | regional |
b. | hydrothermal | d. | shock |
48. Rocks resulting from shock metamorphism are likely to reveal minerals that underwent _______.
a. | plastic deformation |
b. | hydrothermal alteration |
c. | a phase change |
d. | recrystallization |
49. 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 |
50. 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. |
1. 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.
2. 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.
3. 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.
4. What is an index mineral? What do metamorphic isograds indicate? What is a metamorphic zone?
5. Describe the similarities and differences between schist and phyllite.
6. 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.
7. 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.
8. What metamorphic facies would most commonly be associated with a subduction zone and why?
9. What distinguishes metamorphic grade from metamorphic facies?
10. 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?