1. Metamorphic Rocks Metamorphic Rocks Definitions Definitions• • - -
"Meta"= Change
"Meta"= Change
(Grk)
(Grk) - -
"Morph"= form
"Morph"= form
(Grk)
(Grk)
a rock that has been changed
a rock that has been changed - -
from its original form (
from its original form (
parent
parent
) by
) by
heat
heat , ,
pressure
pressure
, and
, and
fluid activity
fluid activity
into a new rock (
into a new rock (
daughter ).

2. Heat Heat Sources Include..... Sources Include..... Magma Magma • •- -
temperature of magma
temperature of magma - -
composition of magma
composition of magma •
Geothermal gradient
Geothermal gradient • - -
temperature increases with depth of burial
temperature increases with depth of burial - -
core of Earth is warmer than outer crust
core of Earth is warmer than outer crust

3. Uniform Pressure vs Directed Pressure Uniform Pressure
Lithostatic • •
Lithostatic - -
"Lithos"= rock, static= unchanged (pressure)
"Lithos"= rock, static= unchanged (pressure) - -
uniform (aka non-directed)
uniform (aka non-directed) - -
equal intensity from all directions by rocks
equal intensity from all directions by rocks

4. Directed Pressure
one direction of squeezing is much stronger than the others
Minerals align themselves to reduce stress.

5. Types of Metamorphism Types of Metamorphism Contact • Contact •- -
caused by igneous activity
caused by igneous activity • •
Dynamic
Dynamic - -
aka cataclastic
aka cataclastic - -
associated with faults & earthquake zones
associated with faults & earthquake zones • •
Regional
Regional - -
caused by tremendous pressures
caused by tremendous pressures
associated with tectonic plate activity
associated with tectonic plate activity

6. Contact Metamorphism Contact Metamorphism Igneous Intrusions• •
Igneous Intrusions - -
size and type of magma important
size and type of magma important
>
>
mafic magma hotter than felsic
mafic magma hotter than felsic - -
heat decreases away from magma
heat decreases away from magma
>
>
forms a zone of altered country rocks called
forms a zone of altered country rocks called
Aureoles
Aureoles
Sometimes creates a metamorphic rock called a hornfels -in essence a “cooked” rock

7. Hornfels- basically any rock that has been “cooked” and metamorphosed by contact with igneous material (magma or lava).
Often original rock textures are identifiable

9. Dynamic Metamorphism Dynamic Metamorphism • •
aka Cataclastic Metamorphism
aka Cataclastic Metamorphism
associated with Fault Zones • •
associated with Fault Zones - -
Places where the Earth's crust ruptured
Places where the Earth's crust ruptured - -
Rock pulverized
Rock pulverized
>
>
heat and pressure come from movement along the
heat and pressure come from movement along the
Fault
Fault
Mylonite
Mylonite • •
resultant rock is known as a
resultant rock is known as a

10. Regional Metamorphism Regional Metamorphism• •
Most common form of metamorphism
Most common form of metamorphism • •
caused by large scale forces
caused by large scale forces - -
lithospheric plate collision
lithospheric plate collision
covers very large areas • •
covers very large areas - -
metamorphic belts or zones
metamorphic belts or zones - -
Zones are characterized by
Zones are characterized by
Index Minerals
Index Minerals
>
>
form under specific temperatures and pressures
form under specific temperatures and pressures
>
>
metamorphic facies
metamorphic facies
commonly associated with • •
commonly associated with - -
shields: stable areas of crystalline rocks
Shields and Mountains: areas of crystalline rocks

11. Metamorphic Textures Metamorphic Textures • • Foliated Foliated- -
Folios = page or leaf-like
Folios = page or leaf-like - -
rock has distinct banding or layering
rock has distinct banding or layering
>
>
often not smooth like in sedimentary rocks
often not smooth like in sedimentary rocks - -
formed under directed pressure
formed under directed pressure
Non-foliated • •
Non-foliated - -
no distinct layering character
no distinct layering character - -
often a massive crystalline texture
often a massive crystalline texture - -
formed under uniform pressures
formed under uniform pressures

12. Foliated Texture
Foliated Texture

13. Foliated Textures Foliated Textures • Slatey Slatey • • Schistose- -
looks like blackboard
looks like blackboard - -
distinct bands of minerals
>
>
dull surface
dull surface - -
visible grains
visible mineral grains - -
smooth, thin layering
smooth, thin layering
>
>
garnets, staurolites
garnets, staurolites - -
breaks into flat slabs
breaks into flat slabs - -
may have shiny
may have shiny
>
>
referred to as slatey cleavage
referred to as slatey cleavage
appearance - -
no mineral grains visible
no mineral grains visible
>
>
due to mica minerals
due to mica minerals • •
Phyllitic
Phyllitic • •
Gneissic
Gneissic - -
looks like waxed surface
looks like waxed surface - -
larger grains
larger grains
>
>
has a "sheen" to it
has a "sheen" to it - -
may look like igneous rock
may look like igneous rock - -
may have little "waves" on
may have little "waves" on - -
may have crude banding
may have crude banding
surface
surface
>
>
intensely distorted
intensely distorted
>
>
referred to as
referred to as
crenulations
crenulations - -
different minerals than
different minerals than - -
some small grains visible
some small grains visible
schistose
schistose

14. Foliated MM Rocks Foliated MM Rocks phyllite phyllite slate slate
schist
gneiss
schist
gneiss
MM Rocks that could form as a shale (sedimentary) parent rock is
MM Rocks that could form as a shale (sedimentary) parent rock is
exposed to increasing directed pressure and temperature

15. Migmatite- a very high grade metamorphic rock that has begun to partially melt

16. Migmatite- note the “blobs” of quartz

17. Non-foliated textured MM Rocks Non-foliated Rocks•
Marble: -
metamorphosed
limestone • •
Quartzite:
Quartzite: - -
metamorphosed
metamorphosed
quartz sandstone
quartz sandstone

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

19. Metamorphic Zones
Metamorphic Zones

20. Metamorphic Zones-Map

21. Metamorphic Facies Metamorphic Facies Hornfels
distinctive metamorphic mineral assemblages that occur in well-defined P & T regions and named after the key rocks (and associated lithologies) found
Hornfels

22. Blueschist
Can be both a rock, and a facies characterized by specific temperature and pressures
The rock commonly has high temp and pressure
It commonly has
Glaucophane & Lawsonite
Usually has smaller
Crystals relating to
mineralogy

23. Blueschist
Can be both a rock, and a facies characterized by specific temperature and pressures
The facies is that constrained by the temp and pressure necessary to metamorphose a basalt parent rock into a blueschist

24. Greenschist
Can be both a rock, and a facies characterized by specific temperature and pressures
The rock commonly has low to intermediate temp and pressure
It commonly has
Chlorite, Actinolite
Serpentine, and
Epidote.
Usually has small
Crystals relating to
mineralogy

25. Greenschist
Can be both a rock, and a facies characterized by specific temperature and pressures
The facies is that constrained by the temp and pressure necessary to metamorphose a basalt parent rock into a schist

26. Amphibolite
Can be both a rock, and a facies characterized by specific temperature and pressures
Rock contains predominantly amphiboles
Like hornblende and actinolite

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