Definition

Noun: A fragment or inclusion of a rock that is foreign to the main igneous rock body in which it is found. It is a piece of older rock that has been picked up and surrounded by magma during its ascent and solidification.

Usage

The term is used specifically in geology to describe an enclosed rock fragment that differs in composition and origin from the surrounding igneous matrix. * The geologist identified a large xenolith of sandstone within the basalt flow. * These peridotite xenoliths provide direct samples of the Earth's upper mantle.

Advanced Usage

• "Xenolith suite": A collection or group of different xenoliths found within a single igneous body, indicating the variety of rock types through which the magma passed.
  • The kimberlite pipe contained a diverse xenolith suite, including eclogite and granulite.
• "Xenolith-bearing": Used as an adjective to describe an igneous rock that contains xenoliths.
  • The roadcut exposes a highly xenolith-bearing andesite.

Variants and Related Words

• Xenocryst (n): A single crystal foreign to the igneous rock in which it is found, as opposed to a fragment of rock (xenolith).
  • Diamond is often found as a xenocryst in kimberlite.
• Xenolithic (adj): Of or relating to a xenolith; having the characteristics of a xenolith.
  • The rock exhibited a distinct xenolithic texture.

Synonyms

• Inclusion: A general term for any foreign material enclosed within a rock. (Note: All xenoliths are inclusions, but not all inclusions are xenoliths; inclusions can also be of the same origin.)
• Enclave: A mass of rock of different composition enclosed within another. (This term is broader and can be used in both igneous and metamorphic contexts.)

Related Concepts

• Country rock: The pre-existing rock into which an igneous body intrudes. Xenoliths are pieces of this country rock that have broken off and been incorporated.
• Magma assimilation: The process by which magma melts and incorporates surrounding country rock; xenoliths represent incompletely assimilated pieces.

Noun

1. (geology) a piece of rock of different origin from the igneous rock in which it is embedded