Metamorphism Flashcards
Define metamorphism.
Rocks changing in response to changes in temperature and pressure
What factors does the product rock of metamorphism depend on?
Chemical composition of original rock, temperature, pressure, and stress
What are the two ways a rock can be heated as part of metamorphosis?
Burial and nearby igneous intrusion
What is the temperature range of heat metamophism?
Starts around 200ºC and ends around 650-800ºC
Why does metamorphism stop around 650-800ºC?
Because that’s the temperature where crustal rocks start to melt
What types of rocks does metamorphism usually affect?
Sedimentary
What happens to carbonates when they are heated?
Carbon dioxide is expelled.
What happens to clays when heated as part of a metamorphic process?
Water is expelled to produce mica
What generally happens to the grainsize of a mineral under metamorphosis?
Becomes coarser.
With increasing pressure, _________ minerals are formed.
Denser
What is the distinction between high and low grade metamorphism?
Low = 200-500ºC and mostly low pressures
High = >500ºC with high pressures
What temperatures does low grade metamorphism usually occur at?
200ºC to 500ºC
Above what temperature is metamorphism usually high grade?
500ºC
Why does high temperatures usually mean high pressures too, in terms of metamorphism?
High temperature metamorphism is usually the result of burial, which usually has higher pressures.
What is differential stress?
When pressure on a rock varies in different directions.