Batholith

A batholith is a large mass of intrusive igneous rock (also called plutonic rock) that forms from cooled magma deep in the Earth's crust. Batholiths are defined as having a surface exposure of at least 100 square kilometers (40 sq mi). These massive bodies of rock are typically composed of felsic or intermediate rocks, such as granite, granodiorite, tonalite, and quartz diorite, but can also include more mafic rocks.

Batholiths form over long periods of time through multiple intrusions of magma that gradually accumulate to create a large volume. The magma rises from the Earth's mantle or lower crust, either through fractures or by melting surrounding rock. As the magma ascends, it cools and crystallizes slowly, leading to the formation of large crystals, a characteristic of intrusive igneous rocks.

Over millions of years, erosion of the overlying rock exposes the batholith at the surface. The resistant nature of granitic rock often makes batholiths prominent features in mountain ranges.

Key characteristics of batholiths:

• Large Size: They cover a vast area, exceeding 100 square kilometers.
• Intrusive Origin: They form from magma that cools and solidifies deep within the Earth.
• Slow Cooling: The slow cooling process results in the formation of large crystals (phaneritic texture).
• Composition: Typically composed of felsic or intermediate igneous rocks.
• Exposed by Erosion: They are brought to the surface through uplift and erosion of overlying strata.

Batholiths are significant geological features that provide insights into the processes of magma generation, intrusion, and crustal evolution.