Metamorphism Flashcards
Name the 5 types of change that create metamorphic rocks.
- Recrystallization
- Phase change
- Metamorphic reaction/neocrystallization
- Pressure solution
- Plastic deformation
Metamorph means…
Meta = Change Morph = Form
The preexisting rocks that are altered during metamorphism are called…
Protoliths
Red shale’s (Protolith) metamorphic rock is?
Gneiss
planar fabric that cuts through the rock
Foliation
What is marble’s protolith?
Limestone
The agents of metamorphism are:
heat (T), pressure (P), compression and shear, and hydrothermal (hot water) fluids
Metamorphism occurs between what temperature ?
250-850 degrees Celcius
What is metamorphic grade?
measure of the intensity of T and P conditions that lead to alteration
What is hydrothermal alteration? Another name?
Hydrothermal fluids speed up chemical reactions and add or subtract elements. Also called: metasomatism
Why does foliation occur?
because the rocks have been subjected to compression and/or shear and they have a significant component of platy minerals
Compression is…
a stress that is greater in one direction
How are compression and pressure different?
Compression is a stress that is greater in one direction.
Pressure is a stress that is of equal magnitude in all directions.
Equant vs. Inequant
Roughly equal in all directions vs. dimensions are not all the same
What are the two subdivisions of metamorphic rocks?
Foliated and non-foliated
Non-foliated rocks
have no planar fabric evident because they lack inequant minerals and/or they recrystallized without differential stress
Slate…
is a fine-grained, low-grade metamorphic shale. It has a distinct foliation called slaty cleavage.
a fine-grained mica-rich rock that forms by the metamorphic alteration of slate. With further alteration, this turns into schist.
Phyllite
A fine to coarsely crystalline rock with larger micas indicating medium-to high-grade metamorphism. It has a distinct foliation from large micas called schistosity.
Schist
Gneiss
has distinct compositional bands, composed of light bands of felsic minerals (quartz and feldspars) alternating with dark bands of mafic minerals (biotite or amphibole).
What is a migmatite?
a partially melted gneiss; it has features of both igneous and metamorphic rocks.
Light-colored minerals that melt at lower T.
Dark-colored minerals that melt a higher T.
Felsic
Mafic
a fine-grained rock from the baked margin of plutonic intrusions. It is often extremely hard and durable.
Hornfels
What do non-foliated rocks lack?
A planar fabric
Quartzite is a metamorphic rock of…
Quartz sandstone (protolith)
A metamorphic facies is…
a set of mineral assemblages that indicate a certain range
of P and T conditions
Blueschist metamorphism is associated with what type of plate boundary?
ocean crust subducting beneath a continent
Contact metamorphism typically produces metamorphic rocks that are called …?
Hornfels
