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GEO LECTURE > metamorphic > Flashcards

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
Q

High-grade metamorphism causes

A

recrystallization and growth of visible crystals

23
Q

Foliation

characterisic of what rocks

A

nearly flat arrangement of mineral grains or structural features

although all rocks can have it, it’s moslty metamorphic

23
Q

High-grade metamorphism causes

A

recrystallization and growth of visible crystals

24
Q

Low-grade metamorphism makes rocks

A

compact and more dense

25
Q

what is foliation a characteristic of?

A

regional metamorphic rock

26
Q

what is foliation driven by?

A

compressional stress to develop parallel alignment

27
Q

ex of Foliation

A

Parallel alignment of micas
Parallel alignment of flattened pebbles
Compositional banding
Split into tabular slabs

28
Q

nonfoliated rocks develop in what type of env.

A

deformation is minimal and parent rocks are made of stable minerals with simple comp

29
Q

before metamorphism processes vs after

A

before: confining pressure
after: differiental stress

30
Q

slate

A

foliated with rock cleavage, made from volcanic ash or shale

31
Q

phyllite

A

glossy sheen and wavy surface

32
Q

schists

A

formed by regional metamorphism of shale

33
Q

gneiss

A

banded metamorphic rock that may have intricate folds

34
Q

marble

A

coarse crystalline rock
From metamorphism of limestone

35
Q

quartzite

A

very hard because of fused quartz grains
From metamorphosed quartz sandstone

36
Q

naming crystals with accessory minerals

A

add a prefix that represents the accessory mineral (large crystal)

37
Q

what do metamorphic rocks make up?

A

c.c and cores of mts

38
Q

how do the mineral grains behave when under differental stress

r

A

rotate perpendiculat to direction of max stress

39
Q

foliated

A

slate
phyllite
schist
gneiss

40
Q

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

A

regional metamorphism vs lithification

41
Q

whaat does the cishcu schist tell you abt tge history of the grandcanyon

A

used to a mountain

42
Q

why can we see vishnu shcist

A

layers of sedimentary rock above it were eroded, so it can existelsewhere except they just werent eroded

GEO LECTURE (19 decks)

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