metamorphic Flashcards

1
Q

metamorphism

A

transformation of one rock type to another due to increase in temp and/or pressure

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2
Q

how are metamorphic rocks produced? what are these rocks called?

A

preexisting igneous, sedimentary, metamorphic rocks (parent rock)

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3
Q

Explain when the rock stops metamorphizing? why does it metamorphize

A

when it reaches a state of equilibrium with new env.

parent isn’t in equilibrium

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4
Q

what changes happen during metamorphism?

A

change in mineralogy, texture, or chem comp

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5
Q

where do most metamorphic changes occur?

A

high temp and pressures of mantle

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6
Q

Low-grade metamorphism

A

low temps and low pressures produce slight changes

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7
Q

low-grade metamorphism ex

what kind of agent

A

shale(loosely packed)–> slate (tightly packed)

differnetial stress

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8
Q

high grade metamorphism

A

high temps and high temps produce substantial changes where parent rock can’t be identified

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9
Q

ex of high grade metamorphism

A

granodiorite(randomly oriented minerals) –>folded gneiss (segregated and deformed minerals) foliation

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10
Q

metamorphism occurs in 2 settings:

A

contact metamorphism
regional metamorphism

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11
Q

contact/thermal metamorphism

A

intruding magma heats adjacent rock to temp for metamorphism

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12
Q

regional metamorphism

A

rock subjected to high temp and pressure during mt-building and large scale deformation

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13
Q

what are the agents of metamorphism

which are for regional and contact

A

heat, confining pressure, differential stress, chemically active fluids

contact: heat/magma
regional: pressure and stress

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14
Q

what does the agent: heat, trigger? and 2 sources?

A

chem reactions sparking recrystallization and formation of new minerals

intruding magma (oven)
buried in depth

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15
Q

Confining pressure

A

pressure increases with depth since thickness of overlying material is greater and forces applied in all directions

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16
Q

what does confining pressure trigger

A

recrystallization of new minerals and spaces of grains are closes (more compact), more dense, deformation by decreasing volume

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17
Q

differential stress

A

rock bodies become highly crumpled bc during mt-building bc of unequal forces in dif directions

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18
Q

rocks exposed to differential stress are shortened in what direction? elongated?

A

direction of greatest stress
direction perpendicular to greatest stress

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19
Q

surface env with low temp vs high temp response to differential stress

A

low: brittle
high: ductile (foliations)

20
Q

chemically active fluids
what do they act as

minerals tend to recyrstallize and grow in what direction

A

hydrothermal fluid rich in ions
catalysts for recrystallization

perpendicular to compressional stresses

21
Q

2 types of metamorphism caused by chemically active fluids

A

changes arrangement and shape of mineral grains
change chem.comp

22
Q

what is foliation a characteristic of? what is it driven by?

A

region metamorphic rocks
compressional stress

23
Q

what are the agents of metamorphism

A

heat, confining pressure, differential stress, chemically active fluids

23
Q

Low-grade metamorphism makes rocks

A

compact and more dense

23
High-grade metamorphism causes
recrystallization and growth of visible crystals
23
Foliation | characterisic of what rocks
nearly flat arrangement of mineral grains or structural features | although all rocks can have it, it's moslty metamorphic
23
High-grade metamorphism causes
recrystallization and growth of visible crystals
24
Low-grade metamorphism makes rocks
compact and more dense
25
what is foliation a characteristic of?
regional metamorphic rock
26
what is foliation driven by?
compressional stress to develop parallel alignment
27
ex of Foliation
Parallel alignment of micas Parallel alignment of flattened pebbles Compositional banding Split into tabular slabs
28
nonfoliated rocks develop in what type of env.
deformation is minimal and parent rocks are made of stable minerals with simple comp
29
before metamorphism processes vs after
before: confining pressure after: differiental stress
30
slate
foliated with rock cleavage, made from volcanic ash or shale
31
phyllite
glossy sheen and wavy surface
32
schists
formed by regional metamorphism of shale
33
gneiss
banded metamorphic rock that may have intricate folds
34
marble
coarse crystalline rock From metamorphism of limestone
35
quartzite
very hard because of fused quartz grains From metamorphosed quartz sandstone
36
naming crystals with accessory minerals
add a prefix that represents the accessory mineral (large crystal)
37
what do metamorphic rocks make up?
c.c and cores of mts
38
how do the mineral grains behave when under differental stress | r
rotate perpendiculat to direction of max stress
39
foliated
slate phyllite schist gneiss
40
what process might be responsible for the formation of the vishnu schist? how does this processs differ from the process that formed sedumentary rock on top
regional metamorphism vs lithification
41
whaat does the cishcu schist tell you abt tge history of the grandcanyon
used to a mountain
42
why can we see vishnu shcist
layers of sedimentary rock above it were eroded, so it can existelsewhere except they just werent eroded