Granite, a common igneous rock, is composed of quartz, feldspar, and mica. When granite is subjected to intense heat and pressure deep within the Earth's crust, it undergoes metamorphism, transforming into a new type of rock. This process changes the rock's texture, mineral composition, and overall appearance.
Here's what happens during the metamorphosis of granite:
1. Recrystallization: The intense heat causes the existing minerals in the granite to recrystallize, forming larger and more tightly packed crystals. This process can also create new minerals that weren't present in the original granite.
2. Foliation: The pressure applied during metamorphism can cause the minerals to align in a specific direction, giving the rock a layered or banded appearance. This layered structure is called foliation.
3. Mineral Changes: The chemical composition of the rock can change during metamorphism, as new minerals form and old ones are altered. For example, feldspar can transform into a new mineral called gneiss.
Different Types of Metamorphosed Granite:
The specific type of rock that results from metamorphosed granite depends on the intensity and type of metamorphism. Some common types include:
* Gneiss: A coarse-grained metamorphic rock with a distinct foliation. It often has a banded appearance due to the segregation of different minerals.
* Migmatite: A mixed rock with both igneous and metamorphic characteristics. It forms when granite partially melts during metamorphism, resulting in streaks of molten rock within the metamorphic matrix.
* Schist: A metamorphic rock with a distinct foliation, often containing mica minerals that give it a shiny appearance.
* Hornfels: A metamorphic rock that forms when granite is heated by nearby magma or lava. It has a fine-grained texture and is often dark in color.
Significance of Metamorphosed Granite:
Metamorphosed granite is a common rock type found in mountain ranges and other areas of tectonic activity. It can be used in building materials, landscaping, and other applications. The study of metamorphic granite can also provide insights into the geological history of a region and the processes that occur deep within the Earth's crust.
