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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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The KL-2 pipe, meanwhile, is a multiphase diatreme facies complex with at least four distinct phases of tuffistic (volcaniclastic) serpentine kimberlite breccia which, again, are locally rich in mantle xenoliths and xenocrysts.
The graben, nearly symmetrical and defined by major faults along each margin [1, 12, 18, 37], may be subdivided into three main segments (Figure 4): (1) the northwestern part, between the Asuncion and Paraguari townships, indicated also by the intragraben Ypacaray rifting and by the presence of Naalkaline mafic-ultramafic plugs carrying mantle xenoliths (Asuncion Province; age between 66 and 39 Ma; cf.
Kilbourne xenoliths in this study consisted of pyroxenites, lherzolites and mafic granulites.
Kaersutite and pargasite are amphiboles typical of alkaline basic rocks and metasomatised mantle xenoliths and their formation occurs early during the crystallization process (e.g.
CPC is actively seeking pathways to help expand the capacity for M/WBEs in New York City and the state by investing in the growth of organizations like Xenolith who share a mission; of using a community-based approach to expanding the supply of affordable housing and improving overall housing quality.
Inclusions were found at ~10% of localities, and include both autoliths and xenoliths. Autoliths consist of any Marginal Zone lithology hosted within a younger Marginal Zone lithology whereas xenoliths consist of Paleoproterozoic(?) gneiss and pervasively recrystallised, ca.
Some of them entrain deep crustal and mantle xenoliths to the surface, providing the only direct rock samples of the lithosphere available to us.
Albite occurs abundantly in fractures and as drusy coatings on altered granitic xenoliths in the Coal Hill vein.
The nature of the subcontinental lithospheric mantle (SCLM) of the Slave is particularly well defined through geophysical and xenolith data.
Meyer (1937-1995) for his contributions to the petrology and mineralogy of mantle-derived xenoliths and kimberlitic rocks and for his services to the mineralogical community.
In one unusual occurrence a xenolith of hornfelsized shale was observed in situ, in the sill near the contact; the xenolith, about 1 meter across, was brecciated throughout and permeated by a dense network of narrow fissures lined with labuntsovite and pyrrhotite crystals.