Metamorphic Rocks Quiz

Study Notes

Formed from existing parent rocks transformed by heat and pressure beneath the Earth's surface or at tectonic plate boundaries.
Primary causes of metamorphism: heat, pressure, and chemically active fluids.
During metamorphism, rocks may fold, fracture, or partially melt before reforming.

Low-Grade Metamorphism:
- Lower temperatures and compressional forces lead to minor changes in parent rock.
- Parent rock may remain easily distinguishable post-metamorphism.
High-Grade Metamorphism:
- Results in total transformation of the parent rock, making identification difficult.

Contact or Thermal Metamorphism:
- Occurs when magma intrudes into parent rock, primarily causing temperature changes.
- Hot, ion-rich water can circulate through fractures, inducing chemical changes.
Dynamic Metamorphism:
- Involves rapid pressure application, often in fault zones or impact craters.
- Fault zones produce heat through friction, potentially melting and altering the rock.
- Impact craters identify high-pressure minerals such as stishovite and coesite from meteorite collisions.
Regional Metamorphism:
- Subjected to heat and pressure on a large scale, typically from burial in the crust.
- Associated with large-scale deformation and mountain-building processes.

Provides energy for chemical reactions that form new minerals from original ones.
Heat enables ions in rock to move, migrate, and recrystallize into new minerals.
Sources of heat:
- Contact metamorphism by nearby magma.
- Geothermal gradient increases temperature with depth in the Earth.

Pressure defined as force per unit area; increases with depth due to overlying rock weight.
Two types of pressures:
- Body Force (Confining Pressure): Applied equally in all directions, compressing mineral grains closer together.
- Surface Force (Differential Stress): Operates across surfaces, affecting how rocks deform under stress.