* Granite: Granite is an igneous rock formed from the cooling and solidification of magma. It has a coarse-grained texture with visible crystals of quartz, feldspar, and mica.
* Regional Metamorphism: This type of metamorphism occurs over large areas, typically deep within the Earth's crust, where rocks are subjected to high temperatures and pressures. These conditions cause the minerals in the rock to recrystallize and change their orientation.
* Gneiss: Gneiss is a metamorphic rock characterized by its banded or layered appearance. These bands are formed by the alignment of minerals under intense pressure.
How it works:
1. Heat and Pressure: Deep within the Earth, granite is subjected to intense heat and pressure from tectonic forces like mountain building (orogeny).
2. Mineral Recrystallization: The heat causes the minerals in the granite to become unstable. These minerals recrystallize into new, more stable minerals, like quartz, feldspar, and mica.
3. Mineral Alignment: The pressure forces the newly formed minerals to align themselves perpendicular to the direction of stress. This alignment creates the characteristic banding seen in gneiss.
4. Metamorphic Texture: The recrystallization and alignment of minerals give gneiss a distinct metamorphic texture, often with a foliated appearance (layered).
In summary: Regional metamorphism, driven by heat and pressure, causes the minerals in granite to recrystallize and align, transforming it into the metamorphic rock gneiss.
