Classifying Metamorphic Rocks
HOW METAMORPHIC ROCKS FORM
Rocks buried deep underground that are subjected to extreme heat and pressure or chemical fluids.
They are heated, folded, squashed, stretched out, and put under a lot of pressure.
RECRYSTALLIZATION
Recrystallization occurs under intense temperature and pressure where grains, minerals and rock materials are packed closer together.
This creates a new crystal structure
HOW ARE THE ROCKS HEATED
REGIONAL METAMORPHISM
Molten rock near the rock that heats it up
CONTACT METAMORPHISM
Rocks make contact with magma, but are not melted
Rocks can also be heated by the the crust of the Earth
Temperature of crust increases by 20-30 C degrees per kilometre
CHEMICAL FLUID
HYDROTHERMAL SOLUTION(Dissolved ions in hot water)
Found along ocean floor.
When the solution comes into contact with
colder seawater, it causes chemical reactions
Called "Contact Metamorphosis"
EXAMPLES OF METAMORPHIC ROCKS
FOLIATED
Can Scratch Glass:
Shicst
Gneiss
Can't Scratch Glass:
Slate
Phyllite
NON-FOLIATED
(SCRATCHES GLASS)
Quartzite
Hornfels
TEXTURES OF METAMORPHIC ROCK
FOLIATED/SHEETLIKE
Sheet-like structure that show what direction
pressure was applied.
NON-FOLIATED/GRANULAR
Metamorphic rocks that don't display a sheet
structure.
Can occur from hot intruding igneous rock applying heat
WITHOUT adding pressure to a rock
Also form from rocks containing minerals that dont align under intense heat
WHERE DOES THE PRESSURE COME FROM
Being buried in the ground gives the rocks
their pressure.
Pressure increases as depth increases.
Burial Metamorphism
Rocks formed by burial in sedimentary basins
with low temperatures and pressure.
Results in new minerals