Metamorphic Rocks (L9) Flashcards

1
Q

What does metamorphism mean and involve

A

meta means change and morph means form so it involves a change in form, converting it from one rock type to another

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2
Q

What are the main agents of change?

A

heat, pressure, and chemically active fluids

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3
Q

What are the 3 main types of metamorphism?

A

contact metamorphism - involves heat, uniform pressure

regional metamorphism - involves heat, differential pressure

Metasomatism - involves reaction of minerals with active fluids during the process

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4
Q

When does contact metamorphism commonly occur?

A

when a pre-existing rock is heated by magma of an igneous intrusion, forming a metamorphic halo, or “aureloe” in the adjecent country rock

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5
Q

When does Regional Metamorphism commonly occur?

A

occurs when a pre-existing rock is heated (baked) under unequal pressure (differential stress)

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6
Q

in terms of texture, what are the main diff between contact and regional metamorphism?

A

the orientation of flat and platy or elongates minerals

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7
Q

In contact metamorphism, pressure is ____ and retains a ___

A

uniform (in all direction) and retains a random orientation

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8
Q

In which areas do regional metamorphism generally occur in?

A

areas where 2 lithospheric plates are pressing against one another, and rocks are subjected to differential stress (pressure applied unevenly)

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9
Q

How is foliation and bedding different?

A

foliation is a uniquely metamorphic characteristic, produced by the preferred alignment of platy/elongate minerals while bedding is a sedimentary characteristic

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10
Q

Rocks containing platy/elongate minerals that are subjected to regional metamorphism are ____

A

typically foliated

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11
Q

with increasing metamorphism, shale changes:

A

to slate, to phylite, to schist, and finally to gneiss

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12
Q

What is shale?

A

a sedimentary rock made of microscopic grains of clay and quartz

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13
Q

Why is shale called a parent rock?

A

because it is the rock we start off with

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14
Q

Shale’s property is?

A

very dull and breaks into layers

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15
Q

What do clay minerals from shale begin to transform into next and what is its foliation type called?

A

transforms into small, platy mica crystals that form slate

called Slaty Cleavage

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16
Q

The development of more distinct, sikly sheens due to further growth of platy mica crystals makes the rock ____

A

phylite and the foliation is phyllitic foliation

17
Q

What rock is made from a medium to high metamorphic grade, and the appearance of obvious sparkles?

A

it is Schist and the foliation type is called schistose foliation

18
Q

high t overy high metamorphyic grade, mica grains transform into more tabular, elongate crystals of amphibole or pyroxene. What rock is this and what is the foliation?

A

Gneiss and genissic foliation

19
Q

What is the overall trend with icnreasing temp and differential pressure (metamorphic grade)?

A

foliation becomes more noticeable due to increse in degree of preferential alignment and size of platy/elongate grains

20
Q

What is another way to recognize if a rock is metamorphic?

A

seeing if the rock is made of mineral crystals as opposed to particles

21
Q

Foliated rocks such as slate and phylite are uesd for which purposes and why?

A

for architectural purposes b/c slate is durable and naturallly split into sheets of even thickness

22
Q

Where is Gneiss used in?

A

similar decorative applications as granite, including countertops, headstones, and facing stone

23
Q

Some metamorphic rocks, can have a non-foliated texture if it has undergone ___

A

contact metamorphism

24
Q

Why are platy/elognate crystals randomly oriented?

A

because their growth wasn’t guided by uneven pressure

25
Q

How can we distinguish calcite from quartz?

A

marble, being composed of calcite beraks in a way that tiny little cleavage planes shine in the light

26
Q

Why are non-foliated metamorphic rock marble commonly used in sculptures?

A

b/c it is relatively soft, easy to carve, and has a relatively uniform texture

27
Q

Why are limestones, which are made in the same composition, less desireable than marble?

A

because it tends to be weak along planes of bedding, so it can have the undesireable quality of spltting

28
Q

When does metasomatism occur?

A

when fluids react with a pre-existing rock and alter the chemical composition of minerals within the rock

29
Q

Serpentine

A

a rock formed y metasomatism and a hardness from 3-6

30
Q

What happens if you add another step of fluid interaction to Serpentine and Quartz?

A

forms the mineral talc used in baby powder

31
Q

Jade

A

another type of rock formed by metasomatism, extreme toughnesss, so can be carved into complex designs without breaking