Igneous intrusion

An igneous intrusion is a body of rock formed when magma cools and solidifies beneath Earth’s surface. Its shape and contacts record how magma entered and altered surrounding rock.

Magma: Molten or partially molten rock beneath Earth’s surface, containing dissolved gases and crystals. Magma is the material that cools to form an intrusion.
Magma emplacement: The process by which magma moves into and occupies space within Earth’s crust. Intrusion formation begins when magma enters the crust and makes room.
Skaergaard intrusion: A layered mafic intrusion in East Greenland, exposed in a large, relatively intact section. Its layering preserves evidence of crystallization and differentiation within a magma body.
Extrusive rock: Igneous rock formed when lava or volcanic fragments cool at or near Earth’s surface. Unlike an intrusion, extrusive rock cools at or near the surface.
Porphyry copper deposit: A large, low-grade copper deposit formed around shallow intrusions and associated hydrothermal systems. Intrusive magmas can drive the fluids that concentrate copper near their margins.
Country rock: Pre-existing rock surrounding a geologic body such as an intrusion, fault, or mineral deposit. Its layers and strength influence where magma can travel.
Fracture propagation: The growth of a crack through rock under applied stress. Magma can force open and extend fractures as it advances.
Bushveld Igneous Complex: A vast layered igneous complex in South Africa containing major chromite and platinum-group element deposits. It demonstrates how enormous intrusions can host economically significant mineral layers.
Pluton: A large body of intrusive igneous rock crystallized from magma within Earth’s crust. Pluton names a substantial intrusive body, commonly irregular or broadly discordant.
Magmatic sulfide deposit: An ore deposit formed when sulfide liquid separates from magma and concentrates metals such as nickel and copper. Some intrusions concentrate valuable metals as immiscible sulfide melts settle or accumulate.

Linked from 5 pages