Metamorphic rock

Metamorphic Rocks
Definitions
•

Metamorphic Rock
- "Meta"=
"Meta"= Change
Change (Grk)
- "Morph"= form (Grk)
--

a rock that has been changed
from its original form (
parent ) by
heat , pressure , and fluid activity
into a new rock ( daughter ).


Heat
Sources
Sources Include.....
Include.....
Magma
•• Magma
---

temperature of
of magma
magma
temperature
composition of

of magma
magma
composition

Geothermal gradient
gradient
•• Geothermal
---

temperature increases
increases with
with depth
depth of
of burial
burial
temperature
core of
of Earth
Earth is
is warmer
warmer than
than outer
outer crust
crust
core


Uniform
Pressure
vs Directed Pressure

Uniform
Pressure

Lithostatic
•• Lithostatic
----

"Lithos"= rock,
rock, static=
static= unchanged
unchanged (pressure)
(pressure)
"Lithos"=
uniform (aka
(aka non-directed)
non-directed)
uniform
equal intensity
intensity from
from all
all directions
directions by
by rocks
rocks
equal


Directed Pressure
one direction of squeezing is much stronger
than the others

Minerals align themselves to reduce stress.


Types of Metamorphism
Contact
•• Contact
--

caused by
by igneous
igneous activity
activity
caused

Dynamic
•• Dynamic

aka cataclastic
cataclastic
-- aka
associated with
with faults
faults &
& earthquake
earthquake zones
zones
-associated

Regional
•• Regional

--

caused by
by tremendous
tremendous pressures
pressures
caused
associated with
with tectonic
tectonic plate
plate activity
activity
associated


Contact Metamorphism
Igneous Intrusions
Intrusions
•• Igneous
---

size and
and type
type of
of magma
magma important
important
size
>>

mafic magma
magma hotter
hotter than
than felsic
felsic
mafic

heat decreases
decreases away
away from
from magma
magma
heat
>>

forms aa zone
zone of
of altered
altered country
country rocks
rocks called
called
forms

Aureoles
Aureoles

Sometimes creates a metamorphic rock called a
hornfels -in essence a “cooked” rock

Dynamic Metamorphism

aka Cataclastic
Cataclastic Metamorphism
Metamorphism
•• aka
associated with
with Fault
Fault Zones
Zones
•• associated

-Places where
where the
the Earth's
Earth's crust
crust ruptured
ruptured
Places
-- Rock
Rock pulverized
pulverized
>>

heat and
and pressure
pressure come
come from

from movement
movement along
along the
the
heat
Fault
Fault

Mylonite
resultant rock
rock is
is known
known as
as aa Mylonite
•• resultant


Regional Metamorphism
Most common
common form
form of
of metamorphism
metamorphism
•• Most
caused by
by large
large scale
scale forces
forces
•• caused

--

lithospheric plate
plate collision
collision
lithospheric

covers very
very large
large areas
areas
•• covers
---

metamorphic belts
belts or
or zones
zones
metamorphic
Zones are
are characterized
characterized by
by
Zones
>>
>>

Index Minerals
Minerals
Index

form under
under specific
specific temperatures
temperatures and
and pressures
pressures
form
metamorphic facies
facies
metamorphic

commonly associated
associated with
with
•• commonly
--

shields:
areas ofareas
crystalline
rocks rocks
Shields
andstable
Mountains:
of crystalline


Shields of the World

Metamorphic Textures
Foliated
•• Foliated
----

Folios == page
page or
or leaf-like
leaf-like
Folios
rock has
has distinct
distinct banding
banding or
or layering
layering
rock
>>

often not
not smooth
smooth like
like in
in sedimentary
sedimentary rocks
rocks
often

formed under

under directed
directed pressure
pressure
formed

Non-foliated
•• Non-foliated
----

no distinct
distinct layering
layering character
character
no
often aa massive
massive crystalline
crystalline texture
texture
often
formed under
under uniform
uniform pressures
pressures
formed


Foliated Texture


Foliated Textures

Slatey
•• Slatey
-----

Schistose
•• Schistose

looks like
like blackboard
blackboard
looks
dull surface
surface
>> dull

smooth, thin
thin layering
layering
smooth,
breaks into
into flat
flat slabs
slabs
breaks
>>

referred to
to as
as slatey
slatey cleavage

cleavage
referred

no mineral
mineral grains
grains visible
visible
no

Phyllitic
•• Phyllitic
----

>>

garnets, staurolites
staurolites
garnets,

>>

due to
to mica
mica minerals
minerals
due

-- may
may have
have shiny

shiny
appearance

Gneissic
•• Gneissic

looks like
like waxed
waxed surface
surface
looks
has aa "sheen"
"sheen" to
to itit
>> has

may have
have little
little "waves"
"waves" on
on
may
surface
surface
referred to
to as
as
>> referred

-distinct bands of minerals

-- visible
visiblegrains
mineral grains

crenulations
crenulations

some small
small grains
grains visible
visible
some

-- larger
larger grains
grains
-may look
look like
like igneous
igneous rock
rock
may
-- may
may have
have crude
crude banding
banding
--

>>

intensely distorted
distorted
intensely

different minerals
minerals than
than
different
schistose
schistose


Foliated MM Rocks

slate

phyllite

schist

gneiss
MM
MM Rocks
Rocks that
that could
could form
form as
as aa shale
shale (sedimentary)

(sedimentary) parent
parent rock
rock is
is
exposed to increasing directed pressure and temperature


Non-foliated Rocks
• Marble:
-

Quartzite:
•• Quartzite:

-- metamorphosed
metamorphosed
quartz sandstone
sandstone
quartz

metamorphosed
limestone


Environment of Formation- EOF
look for specific minerals
Map out where those minerals are found
reconstruct T & P for given minerals
Find a modern setting that has similar T & P
using Uniformitarianism

Metamorphic Zones


Metamorphic Zones-Map
Zones-Map
Metamorphic


Metamorphic Facies

distinctive metamorphic
metamorphic lithologies
lithologies that
that occur
occur in
in well
well
•• distinctive
defined areas
areas and
and named
named after
after the
the key
key rocks
rocks found
found
defined

Metamorphic Zones
• Metamorphism is common along most plate boundaries like this.