Metamorphism & Metamorphic Rocks

These flashcards cover key concepts related to metamorphism and metamorphic rocks, including definitions and processes involved.

Metamorphic Rocks

Rocks that have undergone solid-state alteration of preexisting rocks.

Protolith

The preexisting rock that is altered during metamorphism.

Metamorphism

The process by which preexisting rocks are transformed due to changes in temperature, pressure, and/or the presence of reactive fluids.

Foliation

A planar fabric that results from the alignment of platy minerals due to differential stress.

Recrystallization

The metamorphic process where minerals change size and shape without altering their composition.

Neocrystallization

The formation of new minerals from old ones during metamorphism.

Pressure Solution

The process during metamorphism where mineral grains partially dissolve under pressure and reprecipitate where pressure is low.

Plastic Deformation

A process where mineral grains soften and deform under elevated temperature and pressure.

Hydrothermal Fluid

Hot water with dissolved ions that accelerates metamorphic reactions.

Metasomatism

The alteration of a rock's composition through hydrothermal fluids.

Polymorphs

Minerals that have the same chemical composition but different crystal structures due to forming under different conditions.

Migmatite

A partially melted gneiss that contains features of both igneous and metamorphic rocks.

Metamorphic Grade

A measure of the intensity of temperature and pressure conditions that lead to the alteration of rocks.

Prograde Metamorphism

Occurs when a rock is buried deeply and experiences increased temperature and pressure.

Retrograde Metamorphism

Occurs when deep-seated rocks are brought back to the surface and alter due to hydrothermal fluids.

Index Minerals

Minerals that indicate the metamorphic grade of a rock.