Metamorphism

• METAMORPHISM - "To change form"; Greek words meta (change) and morphe (form). Most metamorphic changes occur at: elevated temperatures and pressures.
• 1. CONTACT/THERMAL METAMORPHISM - Triggers when a rock comes in contact with hot temperature or magma; occurs when magma moves into rock. This happens near a body of magma, and changes are driven by a rise in temperature.
• 1. BURIAL METAMORPHISM - Changes in rock occurs when rock is buried at certain depths; alterations are small compared to contact and regional.
• 1. REGIONAL METAMORPHISM - Triggers at elevated pressures. Results in large-scale deformation and high-grade metamorphism. Directed pressures and high temperatures occur during mountain building. This produces the greatest volume of metamorphic rock.
• 1. HYDROTHERMAL METAMORPHISM - When hot water reacts with rocks and alters its chemistry and mineralogy.
• 1. CHEMICALLY ACTIVE FLUIDS - Hot-water based solutions escaping from the mass of magma. Promote crystallization by dissolving original minerals and then depositing new ones.

  • Act as catalysts to promote recrystallization by enhancing exchange of ions.
• 1. HEAT - Provides energy needed to drive chemical reactions.
• 1. PRESSURE - Causes more compact rock with greater density.
• 1. FOLIATED - Has a banded or layered appearance.
• 1. NON-FOLIATED - Does not have banded textures.
• 1. POLIPHEROS - Presence of large crystals.