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Earth and Space Sciences · Glossary

What is Intrusive bodies?

Also known as: pluton · dyke · sill · laccolith · batholith

Definition 5.10 University Earth and Space Sciences — Year 2 · Chapter 5 — Magmas and Their Emplacement

A pluton is any body of magma that solidified within the crust. A dyke is a sheet-like pluton that cuts across the layering of its host rock (or any sheet if the host has no layering); a sill is a sheet-like pluton parallel to the layering. A laccolith is a sill that has thickened by pushing up the overlying layers into a dome. A batholith is a large pluton, or an assembly of plutons, with an exposed area of more than 100 km2100\,\mathrm{km}^{2}.

Shapes of intrusive bodies in a layered host (schematic, not to scale): a feeder dyke cutting across the layers, a sill along a bedding plane, a laccolith doming the layers above it, a dyke cutting up to the surface, and a batholith with blocks stoped from its roof and a contact aureole.
Shapes of intrusive bodies in a layered host (schematic, not to scale): a feeder dyke cutting across the layers, a sill along a bedding plane, a laccolith doming the layers above it, a dyke cutting up to the surface, and a batholith with blocks stoped from its roof and a contact aureole.
The level of neutral buoyancy (schematic). The density of the crust increases with depth, by compaction of sediments and by the change to denser rocks; a magma of fixed density rises while it is lighter than its surroundings (shaded) and spreads out where the two densities meet.
The level of neutral buoyancy (schematic). The density of the crust increases with depth, by compaction of sediments and by the change to denser rocks; a magma of fixed density rises while it is lighter than its surroundings (shaded) and spreads out where the two densities meet.
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