GEOL 101 Chapter 8

What is a metamorphic aureole?

A ring of metamorphic rocks adjacent to an igneous intrusion.

What do we call a metamorphic rock that has coarse-grained texture, minimal amounts of mica, and contains minerals that are segregated into bands?

Gneiss

What would you call a granite that has undergone metamorphism and now exhibits foliation?

Gneiss

Which of the following is a metamorphic rock?

Gneiss

What agent might metamorphose rocks found adjacent to a large magma body?

Hydrothermal solutions

Which of the following is associated with the metamorphic rock phyllite?

Intermediate-grade metamorphism

How will minerals orient when a rock is put under shear stress?

Parallel to the direction of the shear stress.

How will foliation in continental metamorphic rocks formed during subduction be oriented?

Perpendicular to the direction of plate movement.

How will minerals grow when a rock is put under normal stress?

Perpendicular to the direction of the greatest stress.

How will minerals orient when a rock is put under normal stress?

Perpendicular to the direction of the greatest stress.

How are metamorphic rocks formed?

Preexisting rock is altered through heat and pressure.

Working in the field, you encounter a metamorphic rock that lacks foliation and is composed primarily of interlocking sand-sized grains that will scratch glass. How should this rock be classified?

Quartzite

Application of low-grade metamorphic forces to a rock causes _______.

an increase in rock density.

What is rock texture?

The way the rock looks.

Why does quartzite not exhibit foliated texture?

There are very few or no tabular minerals in quartzite.

If foliation is to develop in metamorphic rocks, it occurs best at medium- to high-grade conditions because ________.

There is enough heat and pressure to induce recrystallization of any tabular minerals in the rock.

Which of the following is a temperature associated with metamorphism?

400 degrees Celsius

Which of the following metamorphic rocks could have a parent rock(protolith) of shale?

-gneiss -slate -phyllite -schist

Which of the following factors describes the conditions at a zone where contact metamorphism is occuring?

-low pressure -high temperature

Which of the following factors describe the conditions at a zone where low-grade regional metamorphism is occurring?

-low pressure -low temperature

Which of the following factors describe the metamorphic conditions in a subduction zone?

-low temperature -high pressure

Which of the following factors describe the metamorphic conditions at a mid-ocean ridge?

-low temperature -low pressure -hot, watery fluids

Which of the following describes the orientation of the long axes of rocks and mineral grains in relationship to the stress applied?

-the long axis of a rock is parallel to the direction of the weakest stress applied -mineral grains are oriented parallel to the direction of the weakest stress applied.

What is foliation?

Banding in metamorphic rocks that results from the reorientation of minerals.

Why are mineral bands in metamorphic rocks light and dark colored?

Dark minerals rich in iron and magnesium separate from light minerals rich in silica and aluminum.

Which processes result in mineral flattening during metamorphism?

Dissolution followed by crystallization.

Working in the field, you encounter a metamorphic rock that lacks foliation and reacts to hydrochloric acid. How should this rock be classified?

Marble

What do we call a metamorphic rock that has a coarse-grained texture, is dominated by mica, and contains no other notable minerals?

Mica schist

Why do bands of minerals form when rocks are put under normal stress?

Minerals dissolve, atoms migrate to new locations, and minerals reform.

Which of the following best describes confining pressure and the location in which it occurs?

Moderate pressures at shallow depths.

From the following choices, identify the grade of metamorphism and one characteristic mineral associated with each of the metamorphic rocks.

SCHIST -intermediate-grade metamorphism -garnet SLATE -low-grade metamorphism -chlorite GNEISS -high-grade metamorphism -sillimanite

How is quartz sandstone metamorphosed into quartize during contact metamorphism?

Sand grains are fused together because of high temperatures.

What do we call a metamorphic rock that has microscopic to very fine-grained texture, breaks into slabs or sheets and is dull on the surface?

Slate

Do metamorphic rocks look like the preexisting rock from which they form?

Sometimes, but not always

In addition to mineralogic composition, the degree of metamorphism in a rock is also characterized by _________.

Texture