Chapter 7 Flashcards
Metamorphism
When a rock changes due to heat and pressure. It is distinctly different from its mother rock.
Metamorphic Rock
A rock produced by metamorphism
Parent Rock (protolith)
What a metamorphic rock morphs from.
Ductile (Plastic)
Capable of being molded and bend under stress.
What is the parent rock of Marble
Limestone it can also be calcite.
How are metamorphic rocks brought to the surface?
because of erosion and the uplift of mountain belts
Confining Pressure
Pressure applied equally on all surfaces of a body.
What is the pressure gradient under the earths crust?
1 Kilobar for every 3.3 meters of burial in the crust.
stress
A force that applies pressure and usually changes the shape of the object.
Differential Stress
When pressure on a body are not of equal strength in all directions.
What is Shearing?
Movement in which parts of a body slide relative to one another and parallel to the forces being exerted. In simple terms, think of shearing a bolt.
How important is Hot Water(as vapor) in the creation of metamorphic rocks?
It is the most important.
What is Foliation
Parallel alignments of textural and structural features of a rock. It’s kind of like those videos were they fill a tree stump full of epoxy and then they plain it and everything is thin and stretched.
What is Foliation
When a metamorphic rock forms sheets or layers from the direction of pressure that was applied.
Slate
A fine Grained rock that splits easily along flat parallel planes.
Phyllite
A metamorphic rock in which clay minerals have recrystallized into microscopic micas, giving the rock a silky sheen.
What are the characteristics of Schist? (Mr. Mosers favorite rock)
A metamorphic rock characterized by coarse grained minerals oriented approximately parallel. It has crystals that are visible to the naked eye. Its chemical composition is relying on the parent rock as well as the temperature it was formed at and pressure.
Gneiss
A metamorphic rock that was created under intense heat and pressure. You can visibly see the foliation.
What are the characteristics of slate?
Fine grained formed from shale under low heat and pressure.
What are the three types of metamorphism?
- Contact
- hydrothermal
- reginal
What is involved with Contact Metamorphism?
Metamorphism in which high temperature is dominant factor.
What is involved with Hydrothermal Metamorphism?
Metamorphism that involves the interaction of rock with high temperature fluids.
What is a Hydrothermal Vein?
Quartz or other minerals that have been deposited in a crack by hot fluids.
What do we find in hydro thermal veins?
zinc, lead, silver, fold, tungsten, tin, mercury, and to some extent copper.
What is regional Metamorphism?
Metamorphism that takes place deep underground. It takes place over wide areas and generally underground. They usually have foliation i indicating differential stress during recrystallization.
How do Hydrothermal veins form?
When Hydrothermal minerals crystallize within a pre existing fracture in a rock.
What are disseminated ore deposits?
When ore minerals are deposited as fine grains distributed throughout the rock.
What is the most common type of metamorphism?
Regional
What is an index mineral
Determines the pressure and temperature combination under which a rock recrystallizes.
What does the term metamorphic grade refer to?
The temperature at which a metamorphic rock was formed.
What is the order of metamorphic grade for these rocks? slate, schist, Gneiss, and Migmatite.
- Slate
- Phyllite
- Schist
- Gneiss
- Migmatite
What is the unique feature of Migmatite in formation?
A mixed igneous and metamorphic rock, formed when a metamorphic rock partially melts. It is like the twilight zone not fully igneous and not fully metamorphic.
What is retrograde metamorphism?
Changes in the mineral assembly of a metamorphic rock from high grade ot lower grade.
What are the 3 sources of water during metamorphism?
- Magmatic Water
- pore fluids in sedimentary rocks
- Breakdown of hydrous minerals(aka clay shale etc)
What is isotherm in relation to plate tectonics?
A line along which the temperature of rock is the same.
What are metamorphic Facies?
Metamorphic rocks that are formed under the same set of pressure or temperature sensitive minerals.
How is foliation in metamorphic rocks formed within a subduction zone?
Shearing.
How is Amphibole formed?
The circulation of heated seawater through oceanic lithosphere. The water changes the ferromagnesian minerals such as olivine and pyroxene into hydrous mineral amphibole.
What is a hydrothermal vent?
Were water comes out of the crust.
At a convergent plate boundary what accounts for water deep within the earth?
Subduction.
What are the characteristics of Hornfels?
Very fine-grained, nonfoliate, metamorphic rock. The parent rock is most commonly shale or basalt.
What type of metamorphism is Metasomatism.
Metamorphism coupled with the introduction of ions from an external source aka water.
What type of metamorphism is metasomatism associated? with?
Contact
What are the primary ways that metamorphic rocks are different from their parent rocks?
- Texture
2. Mineral Composition
What are Cratons largely composed of?
Metamorphic rocks.
What is a kilobar?
How we measure pressure under the earth. One bar is about the same amount of pressure as we experience on the surface of the earth at sea level.
How is mylonite rock formed?
Rocks in contact along the fault zone that are broken up and crushed when movement takes place.
What is lithostatic pressure?
Pressure that is under the earth’s crust. It is similar to what a diver feels deep under the ocean.
What is prograde metamorphism?
When a rock crystallizes into a higher grade rock.
What is an example of a mineral that is stable over a wide range of temperatures?
Quartz
