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11 Cards in this Set
- Front
- Back
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1) Which foliated metamorphic rock is texturally intermediate between slate and schist? a) Fault breccia b) Quartzite c) Phyllite d) Gneiss |
Phyllite |
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2) Which foliation results from parallel alignment of abundant coarse-grained mica flakes in a metamorphic rock? a) Schistosity b) Gneissic banding c) Aureolic layering d) Micaceous marbling |
Schistosity |
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3) Which response lists the rocks in the order of increasing grain size and increasing grade of metamorphism? a) Schist, slate phyllite b) Phyllite, slate, schist c) Slate, schist, phyllite d) Slate, phyllite, schist |
Slate, phyllite, schist |
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4) Which two metamorphic rocks are composed predominantly of single minerals? a) Schist and granitic gneiss b) Marble and quartzite c) Fault breccia and graphitic schist d) Garnet schist and hornfels |
Marble and quartzite |
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5) Which metamorphic rock exhibits visible textural evidence of having undergone some partial melting? a) Fault breccia b) Slate c) Migmatite d) Foliated hornfels |
Migmatite |
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6) The metamorphic rock that is often used for sculptures, monuments, and building facades, AND that can seriously deteriorate with acid rain because of its composition, is: a) Slate b) Granite c) Marble d) Quartzite |
Marble |
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7) Which metamorphic rock is the product of an igneous intrusion “baking” the surrounding country rock? a) Fault breccia b) Slate c) Migmatite d) Hornfels |
Hornfels |
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1) What are the major differences between contact and regional metamorphism? |
Regional metamorphism is the result of both tremendous pressure and heat. It is thought to occur during plate collision at convergent margins. The pressure necessary suggests that the rocks were buried to at least 10 km deep.
Contact metamorphism is mostly the result of heat. It may be expressed as a metamorphic aureole around an igneous pluton, typically only several hundred meters in thickness.
In both cases, the movement of fluids in and through the rocks aids in the metamorphism |
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Define foliation and describe how it is formed in metamorphic rocks. |
Foliation results from preferential mineral growth. Typically pressure is applied in one major direction. Minerals will tend to recrystallize in the direction of lower pressure, resulting in a “layered” appearance that is foliation. This is NOT to be confused with bedding that may have been present in the original sedimentary rock! |
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3) Quartzite is a non-foliated metamorphic rock. Why? Why is it considered to be one of the strongest and hardest rocks? |
A clean quartz sandstone has no clay minerals present that are necessary to form foliation. It is just quartz. And since it is made of quartz (which is hard and durable anyway), when the quartz grains go through heat and pressure, they recrystallize in a dense network. It all depends on the protolith. |
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4) Imagine that you are the engineer responsible for designing a cut through metamorphic rocks for a new highway. What is one major characteristic of those metamorphic rocks that you should consider in your design? |
The major engineering concerns that result from metamorphic rocks deal with their foliation and slope instability. If the foliation is oriented unfavorably, then the slope will fail. Examples given in the book are dam failures, slope failures, and tunnel failures. |
