METAMORPHIC ROCKS - SLG 8.2.3

• Metamorphic Rocks - are formed formed preexisting rocks which could be igneous, sedimentary, or metamorphic. These preexisting rocks are called parent rocks.
• Parent rocks can undergo metamorphism (originating from the Greek word meta, which means change, and morphe meaning form). This can change the overall composition of the rock.
• Contact Metamorphism - when magma comes into direct contact with the rock, causing the temperature to rise within the rock.
• Regional Metamorphism - happens during mountain building where a very large mass of rocks undergoes immense pressure and heat, causing high-scale deformation

  
• Agents of Metamorphism :

  1. Heat
  2. Confining Pressure
  3. Chemically Active fluids
• 1. Heat - it is the most important agent of metamorphism. It causes chemical reactions that change the chemical composition of the minerals.
• 2. Confining Pressure - due to the thick layer of rocks above the buried rocks, it experiences a confining pressure equally from all sides. This makes the mineral more compact and denser.
• 3. Chemically Active Fluids - mostly made up of water and other volatile substances. This fluid is rich in ions that may react with other minerals, causing the recrystallization of minerals.
• Metamorphic Textures

  1. Foliated - due to immense pressure, some mineral grains are reoriented and aligned at a right angle. This causes a layered texture.
  2. Non-foliated - this happens when metamorphism is slight, and the parent rocks are composed of a simple chemical composition .