Metamorphism

Created by

Mia Tabitha

Cards (41)

what are the three types of metamorphism?
Contact, regional, dynamic
when does the process of metamorphism occur?
when rocks are subjected to sufficient temperature, pressure or fluid activity to change the original mineral composition and texture, thus forming new rocks
which state do these transformations take place in?
solid
what do the types of metamorphic rock formed depend on?
composition and texture of parent rock, agents of metamorphism, and the amount of time that the rock was subjected to the agents of metamorphism
what are the three agents of metamorphism?
temperature, pressure and fluids
what do we call metamorphic minerals which can be used to identify the temperatures at which they were formed?
geothermometers
what do we call the increase in temperature with increasing depth?
the geothermal gradient
what is the rate of temperature increase seen with depth?
30 degrees for every km -1
what do we call metamorphic minerals which can be used to identify the pressure it was formed at?
geobarometers
what is the rate by which pressure increases as the depth does?
0.3 - 0.4 kilobars per km
what does increased pressure on the rocks lead to?
recrystallisation of minerals
what does increased temperature on the rocks lead to?
recrystallisation of minerals
what is produced if the stress is equal from all directions?
non foliated metamorphic rocks
what is produced if the stress is not equal from all directions?
foliated metamorphic rocks
why do heat, pressure and fluids enhance metamorphism?
they increase the rate of chemical reactions
what is another word for foliation?
layering
what is metamorphism in response to temperature increase called?
prograde metamorphism
what is metamorphism in response to temperature decrease called?
retrograde metamorphism
what is regional metamorphism?
when temperature and pressure increase at depths
what is regional metamorphism associated with?
continental collision and subduction zones and mountain building
what is contact metamorphism?
when magma intrudes and rises close to or all the way to the surface, causing a temperature increase which causes contact metamorphism
what kind of rock does contact metamorphism affect?
shallow or surface surrounding rocks which we call country rocks
what does contact metamorphism typically lead to?
the development of metamorphic zones parallel to the contact between the intrusion and the country rock
what is dynamic metamorphism?
caused by high shear stresses associated with fault zones
which type of metamorphism occurs at the lowest temperatures?
dynamic
what are the products of dynamic metamorphism?
cataclastic rocks and mylonites
what are mylonites made from?
long stretched out mineral crystals
what do metamorphic zones formed by contact metamorphism comprise?
a contact aureole
what is a contact aureole?
the area surrounding rock that has been metamorphosed due to being in contact with an igneous intrusion
what is the original rock called?
protolith
what are the two types of pressure which solid rock can be subjected to?
confining and directed pressure
what is confining pressure?
general pressure applied uniformly on all sides to a material.
what is directed pressure?
force exerted in a particular direction
what is the change in a rock's composition by fluid transport of a chemical substance into or out of it called?
metasomatism
what is metasomatism?
the change in a rock's composition by fluid transport of a chemical substance into or out of it
which is the most widespread, common type of metamorphism?
regional
name a volcanic mountain belt which shows regional metamorphism?
the andes of South America
name a mountain chain produced by continental-continental collision which shows regional metamorphism?
the Himalayas of central asia
what happens to grain size as metamorphic grade increases?
increases
what is foliation?
a set of flat or wavy parallel cleavage planes produced by deformation of igneous and sedimentary rocks under directed pressure