GEO 303 Metamorphic Rocks

Low Grade

Small changes in texture/mineralogy of parent rock (protolith)

High Grade

Extreme changes in texture/mineralogy of parent rock (protolith)

Regional Metamorphism

• affects large area

• HIGH temperature/HIGH pressure & shear stress

Contact Metamorphism

• Achieved chiefly by application of heat to rock surrounding cooling body of magma (batholith)

• HIGH temp/LOW pressure

Dynamic Metamorphism

• achieved chiefly by application of shear stress

• LOW temp/HIGH pressure

Foliation

parallel alignment of platy or elongate material grains in rock caused by direct stress

Salty cleavage

• parallel alignment of mica flakes in fine-grained metamorphic rock

Schistosity

• large mica grains parallel to one another

Gnessic Layering

• discontinuous light and dark layering (or banding ) due to mineral segregation

Slate

• low-grade

• fine-grained

• foliated

• splits along cleavage

Phyllite

• medium grade

• foliated

• sheen surface (b/c fine grained mica)

schist

• medium grade

• foliated

• rich in mica & sheets parallel to each other

gneiss

• high grade

• foliated

• layered with dark and light bands

amphibolite

• high grade

• weakly foliated

• rich in hornblende

quartzite

• high grade

• non-foliated

• quartz sandstone

marble

• high grade

• non-foliated

• limestone

serpentinite

• high grade

• non-foliated

• green