* Igneous Intrusions: When molten rock (magma) pushes its way through existing rock layers, it cools and solidifies, forming igneous intrusions.
* Heat Transfer: The intrusion brings intense heat to the surrounding rocks. This heat can be substantial, often exceeding 1000°C (1832°F).
* Metamorphism: This extreme heat causes the existing rocks to undergo changes in their mineral composition, texture, and structure. This process is known as metamorphism.
* Contact Zone: The metamorphic changes are most intense directly adjacent to the igneous intrusion, forming a zone of contact metamorphism. The zone can extend outward for some distance depending on the size and temperature of the intrusion and the composition of the surrounding rock.
Key Points:
* Types of Metamorphic Rocks: Contact metamorphism often produces rocks like hornfels, marble, and quartzite.
* Intensity of Metamorphism: The intensity of the metamorphic changes decreases with distance from the intrusion.
* Other Factors: The composition of the surrounding rock and the duration of the heat exposure also influence the resulting metamorphic rock.
Example: If a granite intrusion (igneous rock) pushes its way through a layer of limestone, the heat from the intrusion will transform the limestone into marble.
In summary, the presence of metamorphic rock next to an igneous intrusion is a result of the heat from the intrusion causing the surrounding rocks to undergo metamorphic changes.
