Metamorphic Grade "الصخور المتحولة"

Changed form” rocks
Produced from preexisting
Igneous rocks
Sedimentary rocks
Other metamorphic rocks

Metamorphism
Takes place where preexisting rock is subjected to temperatures and pressures unlike those in which it formed
Degrees of metamorphism
Exhibited by rock texture and mineralogy
Low-grade (e.g., shale becomes slate)
High-grade (obliteration of original features)

Metamorphic settings
Contact, or thermal, metamorphism
Occurs near a body of magma
Changes are driven by a rise in temperature
Regional metamorphism
Directed pressures and high temperatures during mountain building
Produces the greatest volume of metamorphic rock

Metamorphic agents
Heat
Pressure (stress)
Confining pressure – from burial
Differential stress – occurs during mountain building
Chemically active fluids
Mainly water and other volatiles
Promote recrystallization by enhancing ion migration