Metamorphic Flashcards
How do metamorphic rocks form?
when a pre-existing undergoes a solid-state change in response to the modification of its environment at depth
What are in meta rocks?
meta minerals, these are new minerals that grow in place under metamorphic conditions
What are groups of minerals called?
Mineral assemblies
How are meta textures defined?
alignment of mineral grains
how do meta minerals and textures form?
Recrystallization
What is phase change?
transform one mineral to another with the same chemical composition but different atomic structure (polymorphs)
Define Neocrystallization
growth of a new mineral
How does neocrystallization happen?
pressure solution, wet rocks get squeezed, parts dissolve, new minerals precip out
How does plastic deformation work?
rocks get squeezed or sheared at elevated temps or pressures causing mineral grains to align and develop foliation
What causes metamorphism?
heat
What happens when you go deeper into Earth?
Temps and pressure rises
What happens if you subject rocks to pressure?
causes atoms to get tighter
how do Earth’s temps increase
~25 degrees celcius/km, at 20km ~500 celsius
What is the most formed temperature?
~250-800 degrees
how is pressure measured?
0.3 kbar/km, 1 kbar=14,000 psi
What kbar measurement forms the most rocks?
3-12 bars
what is it called when a material is squeezed or sheered unevenly from different directions?
differential stress
Describe normal stress vs sheer stress
normal: push or pull, perpendicular to surface, smash of pizza dough
sheer stress: push or pull, parallel to surface, making a pb&j
List 4 foliated and non foliated rocks
Foliated:slate, phyllite, schist, gneiss
Non foliated: Hornfels, marble, quartzite, amphibolite (can be foliated)
Is all metamorphism the same?
no
How is the metamorphic grade measured? (Low, intermediate, High)
low-200-400 degrees celsius
Int-400-600 degrees Celsius
High-over 600 degrees
What is it called when we get groups of minerals under different metamorphic conditions?
mineral assemblies
What is a particular mineral whose pressure and temp conditions are well known?
Index mineral
where does metamorphism occur?
contact metamorphism, adjacent to igneous intrusions
Describe regional metamorphism
occurs over large areas, results in continental collusion, produces foliated meta rocks
