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 ?
However since the processing of the bulk samples started shortly after they arrived at Lakefield no special attention was given to the presence or lack of xenolithic material in the two bulk samples since it's significance was not known until the beginning of this year.
However, prior to the bulk sampling, additional samples were taken to determine whether the xenolithic portion of the outcrops were diamond rich or diamond poor.
Six of the samples LAL232, 234, and 236 were collected to be specifically representative of the xenolithic material (oblong football shaped masses of mica and actinolite), while samples LAL 233, 235 and 237 consist mostly of the fine grained host rock matrix hosting the xenoliths.
The xenolithic material (composed of talcose, actinolite nodules, varying in size from a few millimeters in diameter up to one meter in diameter) thus far appears to have a much higher diamond content than the host fine grained matrix.