Geology Exam 3- Ch. 8

Geology 1330 with Lytwyn at University of Houston - main campus

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By: Jenn McCaskill
Created: 2011-04-04
Size: 44 flashcards
Views: 117

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Aureole

zone of contact metamorphism found in the country rock surrounding an igneous intrusion

Burial metamorphism

low-grade metamorphism that occurs in the lowest layers of very thick accumulations of sedimentary rock

Confining pressure

equal pressure on all sides

Contact metamorphism

changes in rock caused by the heat from a nearby magma body

Differential stress

unequal in different directions

Foliation

term for linear arrangement texture often exhibited by metamorphic rocks

Gneissic texture

texture in which dark and light silicate minerals are separated and form a banded appearance

Hydrothermal metamorphism

chemical alterations that occur at hot, ion-rich water circulates through fractures in rock

Impact metamorphism

metamorphism that occurs when meteorites strike earth’s surface

Index minerals

mineral that is a good indicator of the environment in which it formed; used to distinguish different zones of regional metamorphism

Metamorphism

the changes in mineral composition and texture of a rock subjected to high temperatures and pressure within the earth

Metasomatism

change in composition by interactions with fluid

Migmatite

a rock exhibiting both igneous and metamorphic rock characteristics; may form when light-colored silicates melt and recrystallize and dark-colored silicates remain solid

Nonfoliated texture

metamorphic rocks that do not exhibit foliation

Parent rock

the rock from which a metamorphic rock formed

Regional metamorphism

metamorphism associated with large-scale mountain building

Rock cleavage

the tendency of rocks to split along parallel, closely spaced surfaces; highly inclined to the bedding planes in the rock

Schistosity

a type of foliation characteristic of coarser-grained metamorphic rock; parallel arrangement of platy minerals such as micas

Slaty cleavage

type of foliation characteristics of slates in which there is a parallel arrangement of fine-grained metamorphic minerals

Cataclastic metamorphism

results from the crushing and shearing of rock during tectonic movement; along fault planes; might produce mylonites: sheared highly deformed rocks

Slate (Foliated)

- low grade metamorphism

- platy minerals too small to be seen

- slaty cleavage

Schist(Foliated)

- upper low-grade to medium grade metamorphism

- increased size of platy minerals

- minerals clearly visible to naked eye

Gneiss(Foliated)

- high grade metamorphism

- light & dark minerals segregated into bands, lenses, and streaks

- Mafic minerals: (biotite & amphibole) concentrated in dark bands

- Felsic minerals: (quartz & feldspar) concentrated in light bands

Migmatite (Foliated)

- Rock begins to melt

- Mafic minerals remain solid

- Silicate-rich liquid invades partially melted rock as veins and stringers

- Softened rock contorts and deforms under differential stress

Amphibolite (Weakly, non-foliated)

- Medium-grade metamorphism of mafic igneous rocks or basalt

- Long, thin crystals are aligned in a common direction (lineation)

- Sometimes separate light bands of feldspar are evident

Granulite (weakly, non-foliated)

- high to very high grade metamorphism of shale, greywacke, and igneous rocks

- Display granular texture consisting of minerals

Greenstone (weakly, non-foliated)

- Form through hydrothermal metamorphism of basalt

Marble (non-foliated)

- Comes from limestone

Quartzite (non-foliated)

- Forms from quartz sandstone

Hornfel (non-foliated)

- Form adjacent to igneous intrusions

Anthracite (non-foliated)

- Fine grained, shiny back rock

Fault breccia (non-foliated)

- Medium to coarse grains, broken fragments in a haphazard arrangement

Agents of metamorphism:

a. Heat

b. Pressure & differential stress

c. Chemically active fluids

Hydrothermal metamorphism

- Heated seawalter and basalt

- Mid-ocean ridges

- Nonfoliated metamorphic rocks typical

contact metamorphism details

- High temperatures

- High geothermal gradient

- Occurs when rocks immediately surrounding a molten igneous body are baked

- These rocks occur in a zone called an aureole

Burial metamorphism details

- Occurs w/ thick accumulations of sediment in basins

- Depth required for this type of metamorphism varies by location

-Confining pressure and geothermal heat contribute to this type of metamorphism

-original rocks/ minerals preserved

Regional metamorphism details

- More extensive

-Occurs in mountain building

-Convergent plate boundaries

-Intense alteration of rock and minerals

-Major tectonic forces

Cataclastic Metamorphism details

a. Generally along fault planes

b. Could produce mylonites

c. Results from crushing and shearing of rock during tectonic movement

Fault breccia V. mylonite

a. Fault breccia: composed of broken and crushed rock fragments; loosely coherent

b. Myolite occurs deeper and is more foliated; it occurs by ductile flow

Tectonic area that blueschists and ecolgites form:

a. Low temperatures

b. Very high – extremely high pressures

About this deck

By: Jenn McCaskill
Created: 2011-04-04
Size: 44 flashcards
Views: 117

About StudyBlue

“Simply amazing. The flash cards are smooth, there are many different types of studying tools, and there is a great search engine. I praise you on the awesomeness.”
Dennis