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
How can we distinguish calcite from quartz?
marble, being composed of calcite beraks in a way that tiny little cleavage planes shine in the light
26
Why are non-foliated metamorphic rock marble commonly used in sculptures?
b/c it is relatively soft, easy to carve, and has a relatively uniform texture
27
Why are limestones, which are made in the same composition, less desireable than marble?
because it tends to be weak along planes of bedding, so it can have the undesireable quality of spltting
28
When does metasomatism occur?
when fluids react with a pre-existing rock and alter the chemical composition of minerals within the rock
29
Serpentine
a rock formed y metasomatism and a hardness from 3-6
30
What happens if you add another step of fluid interaction to Serpentine and Quartz?
forms the mineral talc used in baby powder
31
Jade
another type of rock formed by metasomatism, extreme toughnesss, so can be carved into complex designs without breaking