* Magma Intrusion: Hot, molten magma rises from deep within the Earth's crust and intrudes into pre-existing rocks, like sedimentary or igneous rocks.
* Heat Transfer: The extremely high temperature of the magma (typically 700-1200°C) causes the surrounding rocks to heat up.
* Recrystallization: This intense heat causes the minerals in the existing rock to become unstable and rearrange their structure. This process is called recrystallization.
* Formation of Metamorphic Rocks: The changes in mineral composition and texture due to heat and pressure lead to the formation of new metamorphic rocks. These rocks are often found in a zone surrounding the magma intrusion, known as a contact aureole.
Types of Contact Metamorphism:
* Baked Zone: The area immediately surrounding the magma intrusion experiences the highest temperatures and is often characterized by the formation of hornfels, a hard, dense, non-foliated metamorphic rock.
* Aureole: Further away from the intrusion, temperatures are lower, resulting in less intense metamorphism. This zone may contain rocks like marble (from limestone), quartzite (from sandstone), or other metamorphic rocks specific to the original rock type.
Examples of Contact Metamorphism:
* Batholiths: Large, underground bodies of solidified magma that create extensive contact aureoles.
* Dikes and Sills: Smaller intrusions that create smaller aureoles.
In summary: The surrounding metamorphic rocks are a direct result of the heat and pressure exerted by the magma intrusion. They represent a transformation of the original rock type into a new, metamorphic rock due to the extreme conditions.
