What is a Plutonic Igneous Rock?

Igneous intrusion
Representative Image: Igneous intrusion

In geology, a pluton is a body of intrusive igneous rock (called a plutonic rock) that is crystallized from magma slowly cooling below the surface of the Earth. Plutons include batholiths, stocks, dikes, sills, laccoliths, lopoliths, and other igneous formations. In practice, “pluton” usually refers to a distinctive mass of igneous rock, typically several kilometers in dimension, without a tabular, or flat, shape like those of dikes and sills. Examples of plutons include Denali (formerly Mount McKinley) in Alaska; Cuillin in Skye, Scotland; Cardinal Peak in Washington State; Mount Kinabalu in Malaysia; and Stone Mountain in the US state of Georgia.

The most common rock types in plutons are granite, granodiorite, tonalite, monzonite, and quartz diorite. Generally light colored, coarse-grained plutons of these compositions are referred to as granitoids.

The term originated from Pluto, the classical god of the underworld. The use of the name and concept goes back to the beginnings of the science of geology in the late 18th century and the then hotly debated theories of plutonism (or vulcanism), and neptunism regarding the origin of basalt.

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