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Related to Xenoliths: Phreatomagmatic, Phenocrysts, Plutons


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 It might be outdated or ideologically biased.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 peraluminous nature of most granite plutons points to a significant supracrustal component in the source; this is supported by the close spatial relationship with the Miramichi Group and Trousers Lake Metamorphic Suite, and the common presence of xenoliths or roof pendants of partially assimilated paragneiss in many plutons.
However, comparisons between Ti-clinohumite from the Cienaga Marbles and that found in JAC carbonatites, xenoliths in kimberlites, RGP Alpine peridotites and Archean ultramafics may carry out as shown in Figure 11, highlighting that the Ti-clinohumite analyzed in this study represents not only an almost pure in Mg but also may be considered as the most Mg-rich and TiO2-rich varieties around the world for skarn environments.
The diamonds are produced either by mining the rock, which contains the xenoliths or by mining the soils and sediments that formed as the diamond-bearing rock weathered away.
Hornblende is found in some of the summit samples, as are small gabbroic, plagioclase-magnetite, and ultramafic xenoliths that may represent disaggregated cumulates (Herzer 1971).
Early core drilling strongly suggested that the EJF Inner of ON-K120 was prospective for diamonds due to the abundance of eclogite xenoliths and coarse kimberlite texture.
This study will produce detailed maps of small but representative areas including: (1) detailed topography to a small contour interval; (2) mapping of lithologic textures including megascopic mineralogy, xenoliths, flow foliations, and phenocryst morphology and distribution; (3) mapping of structures such as joints, fractures, and faults; and (4) surface weathering textures.
The outcrops at their Cristal occurrence are stripped of vegetation by exploration crews, and coated with xenoliths, rock fragments encased in volcanic breccias pushed upward from deep inside the mantle.
Unit G is composed of sparsely to moderately porphyritic basalt, with gabbroid xenoliths, plagioclase glomerocrysts and olivine microphenocrysts.
Megacrysts and/or mafic xenoliths are usually absent but clustering of clinopyroxene microphenocrysts is relatively frequent.