Download “changed rocks” – can form from: sedimentary, igneous or other

Metamorphic Rocks
“changed rocks” – can form
from: sedimentary, igneous or
other metamorphic rocks
* Not that kind of change.....
Agents of Metamorphism:
A. Heat: but not hot enough to melt
rock (melted rocks reform into igneous
rocks)
B. Pressure: from burial at great
depths or stress from mountain
building (squeezing) activity
Agents of Metamorphism cont...
C. Chemically active fluids:
mainly water that can carry new
ions that can bond to original rock
This picture shows potentials spots for all 3
agents of metamorphism. Where are they?
Degrees of Metamorphism:
* shows in rock’s texture or mineral
make-up
Low grade: subjected to relatively
mild heat or pressure
often hard to distinguish from
original rock
i.e. shale (igneous) → slate (meta.)
The top 2 are shale. The bottom 2 are slate. Which
one is harder?
High-grade: subjected to high
heat or pressure
- original rock features hard to
see
i.e. quartz sandstone (sed rock
often w/ fossils) → quartzite
Metamorphic settings (areas)
Regional: over large areas (generally mtn
building)
* Produces greatest amt of metamorphic
rock
Contact: occurs near a mass of magma &
bakes surrounding rock
What areas in this picture would be affected by
contact metamorphism? Which by regional?
Metamorphic Textures
Foliated: minerals are parallel
lined up, like pages in a book
slates: fine-grained, easily split
schists: strongly foliated, “platy”
gneiss: silicate minerals obviously
segregated, banded
A
B
So which is the slate, schist
and gneiss?
C
Non-Foliated: contain equal sized crystals,
looks like coarse igneous rock
Marble: parent rock= limestone, calcite
crystals
Quartzite: parent rock= quartz sandstone,
quartz is fused
A
These are
microscopic thin
sections of a
foliated rock and a
nonfoliated rock.
Which is which?
B
Marble
Which one of these
samples would react
with acid?
Quartzite
So is this sample foliated or nonfoliated?