plutonic rocks or intrusive rocks are those that are formed from slow cooling, at great depth and in large masses of magma. They are one of the two types in which igneous rocks are classified depending on their origin. They are thus opposed to volcanic or extrusive rocks, which are formed when the magma (lava) solidifies that emerges from the surface of the Earth's crust, coming into abrupt contact with the atmosphere or bodies of water.

Large masses of this type of rock are called plutons, such as batholiths, laccoliths, sills, and dykes. These masses can emerge on the surface as a result of tectonic activity, which has elevated them, and erosion, which has removed the rocks that covered them.

In quantitative terms, plutonic rocks are the most abundant. They overwhelmingly dominate the composition of the Earth, being made up of the entire Earth's mantle and most of the volume of the crust. The rest of the rocks form only a covering in the surface crust (volcanic igneous rocks, sedimentary rocks and metamorphic rocks) or, in the case of vein rocks, dykes and veins between the other rocks of relatively small volume.

Plutonic rocks, and in general igneous rocks, are the primary rocks, from whose materials the others evolve. They constitute the mass of the telluric (rocky) planets, not just the Earth, formed by the cooling and crystallization, after fusion, of the silicate materials with which the planets are composed during their accretion. They are also present, for identical causes and mechanisms, in the core of gigantic planets, in many of their satellites, or in the largest solid asteroids.

During its formation, the cooling is very slow, thus allowing the growth of large crystals of pure minerals and resulting in a heterogeneous, grainy texture to the naked eye.

Examples of plutonic rocks.

Lacolitos