Metamorphism and Metamorphic Rocks

• Any rock can Undergo metamorphism.
• What is metamorphism?

  The process of rocks changing due to heat and pressure. They transform without melting.
• Protolith is a rock before metamorphism.
• In metamorphism, rocks have the same chemical composition, but new minerals and structures.
• What are the agents of metamorphism?

  Heat, pressure, and fluid activity.
• Agents of metamorphism chanhe’s the rocks’ mineral composition ano texture.
• Heat increases the rate of reaction. Temperature increases as depth increases. Sources of heat includes:

  • Lava
  • Magma
  • Deep burial
• Fluid Activity

  Fluids in sedimentary rocks / coming from magmas accelerate changes. It can cause formation of new minerals.
• Pressure

  It increases as atoms squeezes together. There are two types of pressures: Lithostatic (confining) and Differential pressure.
• Minerals with higher pressure are denser than minerals with lower pressure.
• Lithostatic (confining) pressure

  Caused by weight of overlying and surrounding rock. It is equal in all directions
• Differential pressure

  Directed (not equal in all direction) pressure. It is caused by mountain building. It influences the development of metamorphic structures and textures.
• Types of metamorphism depends on agent, timescale, and location.
• TYPES OF METAMORPHISM: CONTACT

  Low pressure and high temperature

  Long (intrusive) or short (extrusive) timescales

  Localized area

  Magmas/lavas come into contact with existing rock, baking it
• The ”baked zone” in a contact metamorphism is called?

  The aureole.
• The “baked zone” depends on size of intrusion, temperature, and amount of fluid activity.
• TYPES OF METAMORPHISM: DYNAMIC

  Occurs when rocks are grounded and crushed in faults (convergent/transform)

  High pressure, low temp

  Long timescales

  Mylonites: fine-grained rocks.
• What is the most common type of metamorphism?

  Regional metamorphism.
• TYPES OF METAMORPHISM: REGIONAL

  Most common

  Convergent

  Broad range

  Long time scales

  High temperature and pressure (both act as driving for reactions)
• TYPES OF METAMORPHISM: METEORITE IMPACT

  Ultrahigh temperature and pressure

  Short time scale
• TRUE OR FALSE: Metamorphism can happen at all boundaries

  TRUE
• Metamorphism is most common at convergent boundaries.
• Convergent boundaries produces tremendous amount of heat and pressure for metamorphism.
• Index Minerals

  certain minerals form under specific ranges of temperature and pressure.
• What can index minerals be used for?

  Determining the metamorphic grade of a rock.
• What is a metamorphic grade?

  The degree of metamorphic change a rock has undergone.
• What are the metamorphic grades?

  Diagenes (unmodified), Low-grade, medium-grade, and high-grade.
• Classification of Metamorphic rocks: Texture

  Fiolated

  Non-fiolated
• What is a fiolated texture?

  A "foliated texture" refers to a type of rock texture characterized by the presence of parallel layers or bands.
• A fiolated texture is produced by the preferred orientation of platy minerals.
• Where do fiolated-textured rocks occur?

  Convergent boundaries.
• What are nonfiolated texture?

  Nonfoliated texture refers to the texture of a rock that lacks visible layers or bands. It does not have a preferred orientation of minerals.
• Schistosity: wavy layers, at least some are coarse grains.
• Gneissic banding

  Mafic and felsic segregate into alternating bands of minerals.
• FIOLATED METAMORPHIC ROCKS: Amphibole

  composed of mainly amphibole. Can be fiolated or nonfiolated
• FIOLATED METAMORPHIC ROCKS: Migmatite

  mixed with felsic igneous and mafic metamorphic.

  Contains streaks of granite from partial melting.
• Metamorphism series

  Shale —> slate —> Phyllite —> Schist —> Gneiss —> Migmatite
• What are metamorphosed sandstones?

  Quartzite
• What happens to limestone/dolostone when it undergoes metamorphism?

  Marble
• What happens to a basalt if it is metamorphosed?

  It becomes a greenstone