Geology Metamorphism Homework

an increase in rock density

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

replacement or substitution of ions in the pre-existing rock

At a mid-ocean spreading center, alteration of rocks by chemically active fluids causes metamorphism by __________.

The gabbro was heated to 500 °C and buried a few miles below the Earth's surface.

By what process did the gabbro turn into amphibolite?

come in contact with a magma body

Contact metamorphism takes place when rocks _____.

sometimes, but not always

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

hydrothermal solutions

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

mica schist

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

gneiss

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

slate

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?

hot mantle rock rising from deep within the Earth

What is a mantle plum?

a ring of metamorphic rocks adjacent to an igneous intrusion

What is a metamorphic aureole?

banding in metamorphic rocks that results from the reorientation of minerals

What is foliation?

the way a rock looks

What is rock texture?

heat

What is the most efficient agent of metamorphism?

gneissic texture

What kind of metamorphic texture results in the segregation of light and dark mineral bands?

sedimentary, igneous, and metamorphic rocks

What kinds of rocks can become metamorphic rocks? Choose all that apply.

Water migrates into host rock carrying ions to stable minerals in order to facilitate growth of new metamorphic minerals.

What role does hot ion-rich water play in the process of metamorphism?

200-700 degrees Celcius

What temperatures do metamorphism take place at?

Brittle deformation occurred. A transform fault was present.

What would the presence of a fault breccia tell you about the history of an area?

gneiss

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

align perpendicularly to the plane in which the maximum compressive stress is applied

When fine-grained tabular minerals in a rock at depth are subjected to differential stresses, they _________.

fault zones

Where would you find fault breccia?

low pressure, low temperature, hot watery fluids

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

high pressure, low temperature

Which factors describe the metamorphic conditions in a subduction zone?

moderate pressures at shallow depths

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

Regional metamorphism occurs when large segments of Earth's crust are deformed by the collision of two continental blocks

Which of the following describes regional metamorphism?

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

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

low pressure and low temperature

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

high temperature, low pressure

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

intermediate-grade metamorphism

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

Depending on the degree of metamorphism shale is subjected to it can be metamorphosed into slate, phyllite, schist, and gneiss.

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

It occurs at cold temperatures. Metamorphic rocks are broken

Which of the following phrases describes brittle deformation?

They are formed through ductile deformation

Which of the following statements describes a mylonite?

dissolution followed by crystallization

Which processes result in mineral flattening during metamorphism?

hydrothermal metamorphism

Which type of metamorphism may precipitate economically important metallic deposits such as gold and silver?

Garnets have a value of 8 or 9 on the Mohs Hardness Scale, making them very abrasive.

Why are garnets used in sandpaper?

dark minerals rich in iron and magnesium separate from light minerals rich in silica and aluminum

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

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

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

There are very few or no tabular minerals in quartzite.

Why does quartzite not exhibit foliated texture?

quartzite

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?

marble

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

when a preexisting rock is altered through heat and pressure

How are metamorphic rocks formed?

Sand grains are fused together because of high temperatures.

How is quartz sandstone metamorphosed into quartzite during contact metamorphism?

perpendicular to the direction of plate movement

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

perpendicular to the direction of the greatest stress

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?

Parallel to the direction of the shear stress

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

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

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

texture

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

pressure

In addition to temperature, which of the following agents increases with depth in Earth?