Metamorphic Rocks
“Meta” = Change
“morph” = form (both Greek)
A rock that has been changed from its original form (parent) by
HEAT, PRESSURE (over a long time) to form a new rock.
This occurs in the SOLID state at temperatures above ~200 degrees C and below the melting point of the rock
Metamorphic rock is a record of the conditions in the earth’s crust at a given time. The mineral assemblage is a reflection of specific physical and chemical conditions.
PROTOLITH: The original rock before metamorphism.
Metamorphism involves the recrystallization of existing rock, in the solid state.
Great change in temperature and pressure is needed.
This process is ISOCHEMICAL, meaning that the bulk composition of the rock stays the same.
(the protolith and the resulting metamorphic rock have the same overall composition)
