Questions and Answers
Choose the listing that shows the rocks in increasing degrees of metamorphism (from lower- to higher-grade).
What is the protolith of marble?
Limestone
Which of the following locations could not possibly be part of a shield?
A metamorphic rock cannot be formed below 1200°C as all the rock minerals must melt.
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Extremely high temperature of metamorphism is necessary to form chlorite.
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All the possible answers are correct regarding Mylonite?
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Pick out the rock that is nonfoliated.
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Metasomatism requires hot fluids in order to occur.
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Metamorphic facies are identical to metamorphic mineral assemblages.
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Identify a TRUE statement about metamorphic rocks and their characteristic environments.
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Which of the following processes results in the exposure of deeply buried rocks at the Earth's surface?
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Which is NOT a common process by which metamorphic rocks are formed?
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All the possible answers are correct regarding mountain building due to convergent-margin tectonics?
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Recrystallization occurs because thermal energy causes atoms to vibrate rapidly, break existing chemical bonds, and migrate to new positions.
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Roofers use the rock schist to shingle roofs because its foliation, called schistosity, causes it to break in convenient size.
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The mineral sillimanite indicates higher-grade metamorphism than staurolite.
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Schist is a medium-grade foliated metamorphic rock that normally contains micas.
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Which is NOT a cause of banding in gneiss?
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Marble is a favorite material of sculptors because of its relative softness and uniform texture.
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Blueschist is a common metamorphic rock of continental shields.
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If the intrusion of magma melts mafic country rock, the resulting metamorphic rock is a schist or gneiss.
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Metamorphic aureoles typically contain nonfoliated rock like hornfels.
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A supercritical fluid permeates rock very thoroughly because it has characteristics of both liquid and gas.
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Which of the following is NOT required for pressure solution to occur?
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When geologists say metamorphic grade, they're referring to the general degree of metamorphism of a rock; when they say facies, they mean a subset of the broad temperature and pressure conditions in which metamorphism can occur.
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The sequence of increasing metamorphism of the protolith shale is slate, phyllite, schist, and gneiss.
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Dynamothermal metamorphism produces metamorphic rocks in the depths of mountain ranges.
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Dissolved ions during the process of metasomatism can precipitate to form mineral-filled cracks called veins.
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Contact metamorphism occurs when
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Which process would you most expect during hydrothermal metamorphism near a mid-ocean ridge?
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Study Notes
Metamorphism and Related Concepts
- Increasing degrees of metamorphism range from metaconglomerate (barely metamorphosed) to gneiss without mica (medium-to-high grade), and finally to migmatite (high grade, beginning to melt).
- Protolith of marble is limestone, which transforms through metamorphism.
Geological Features and Locations
- Shields are the oldest regions of Earth's surface; Hawaii, being a hot spot island, cannot be part of a shield.
Metamorphic Processes and Conditions
- Metamorphic rocks require temperatures between 200°C and 850°C; anything above 1200°C leads to melting rather than metamorphism.
- Chlorite forms at low-grade metamorphism, not high temperatures.
- Mylonite forms through dynamic metamorphism and exhibits pronounced foliation due to shear stress within fault zones.
Rock Classifications and Characteristics
- Hornfels is a nonfoliated metamorphic rock formed without differential stress.
- Metasomatism involves the presence of hot fluids, contrasting other processes that may involve different temperature-pressure combinations.
- Different rocks within a metamorphic facies have varying mineral assemblages based on bulk chemistry.
Mountain Building and Tectonics
- Mountain building can result from increased pressure, proximity to magma, and differential stress due to tectonic plate interactions; all can metamorphose surface rocks.
- Exhumation refers to the exposure of deeply buried rocks at the Earth's surface.
Foliation and Rock Usage
- Slate is preferred for roofing rather than schist, due to its ability to cleave into thin, manageable pieces.
- Schist is a medium-grade foliated metamorphic rock typically containing micas.
- Gneiss features compositional banding caused by mineral segregation, not preferential orientation.
Metamorphic Indicators
- Sillimanite indicates higher-grade metamorphism than staurolite, part of the aluminum silicate family.
- Marble's softness and uniform texture make it favored by sculptors.
Miscellaneous Metamorphic Concepts
- Blueschist forms under specific high-pressure, low-temperature conditions and is considered rare.
- Plutonic intrusions melting rock do not produce metamorphic rocks but can generate different rock types.
- Nonfoliated rocks like hornfels are common in metamorphic aureoles due to heat without accompanying shear stress.
Chemical and Physical Changes
- Supercritical fluids can penetrate rock thoroughly due to their dual characteristics of liquid and gas.
- Pressure solutions occur without the need for specific metamorphic facies, relying on uneven stress and atom migration.
Definitions and Processes
- Metamorphic grade reflects the degree of metamorphism; metamorphic facies denote specific temperature and pressure conditions during metamorphism.
- Sequence of metamorphism for shale progresses from slate to phyllite, then to schist and finally gneiss as temperature and pressure increase.
- Hydrothermal fluids can cause metasomatism, altering rock composition and forming mineral veins from dissolved ions.
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Description
Test your understanding of metamorphic rocks in Chapter 7. This quiz covers the hierarchy of metamorphism, featuring terms like metaconglomerate, gneiss, and migmatite. Explore the characteristics and classifications of these rocks.
