Xenolith

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Related to xenolithic: xenocryst, Autolith

xenolith

[′zēn·ə‚lith]
(petrology)
An inclusion in an igneous rock which is not genetically related, such as an unmelted fragment of country rock. Also known as accidental inclusion; exogenous inclusion.

Xenolith

 

a rock fragment that is foreign to the igneous rock in which it occurs. If the igneous rock enclosing the xenolith solidified at a great depth, then the xenoliths are usually greatly altered fragments of those rocks into which the magma intruded. But if the xenoliths are enclosed in the lava of a volcano, then they are usually fragments from the walls of the volcanic vent. The dimensions of the xenoliths vary greatly; they may be as small as individual crystals and their fragments, which can be distinguished only under a microscope (xenocrysts), or as large as several dozens or hundreds of meters.

References in periodicals archive ?
that the fragments are cognate, not xenolithic. However, the debate is now settled: the fragments are indeed xenoliths, and diamond crystals are not products of the kimberlite but, as components of xenoliths, are mere passengers on the kimberlite fast-express to the surface.