Gabbroic xenolith in granite in Rock Creek Canyon, eastern Sierra Nevada, CaliforniaOlivine weathering to iddingsite within a mantle xenolith
A xenolith ("foreign rock") is a rock fragment (country rock) that becomes enveloped in a larger rock during the latter's development and solidification. In geology, the term xenolith is almost exclusively used to describe inclusions in igneous rock entrained during magma ascent, emplacement and eruption.[1] Xenoliths may be engulfed along the margins of a magma chamber, torn loose from the walls of an erupting lava conduit or explosive diatreme or picked up along the base of a flowing body of lava on the Earth's surface. A xenocryst is an individual foreign crystal included within an igneous body. Examples of xenocrysts are quartz crystals in a silica-deficient lava and diamonds within kimberlite diatremes. Xenoliths can be non-uniform within individual locations, even in areas which are spatially limited, e.g. rhyolite-dominated lava of Niijima volcano (Japan) contains two types of gabbroic xenoliths which are of different origin - they were formed in different temperature and pressure conditions.[2]
Although the term xenolith is most commonly associated with inclusions in igneous rocks,[3] a broad definition could also include rock fragments which have become encased in sedimentary rock.[4][5] Xenoliths have been found in some meteorites.[6]
To be considered a true xenolith, the included rock must be identifiably different from the rock in which it is enveloped; an included rock of similar type is called an autolith or a cognate inclusion.
Xenoliths and xenocrysts provide important information about the composition of the otherwise inaccessible mantle. Basalts, kimberlites, lamproites and lamprophyres, which have their source in the upper mantle, often contain fragments and crystals assumed to be a part of the originating mantle mineralogy. Xenoliths of dunite, peridotite and spinel lherzolite in basaltic lava flows are one example. Kimberlites contain, in addition to diamond xenocrysts, fragments of lherzolites of varying composition. The aluminium-bearing minerals of these fragments provide clues to the depth of origin. Calcic plagioclase is stable to a depth of 25 km (16 mi). Between 25 km (16 mi) and about 60 km (37 mi), spinel is the stable aluminium phase. At depths greater than about 60 km, dense garnet becomes the aluminium-bearing mineral. Some kimberlites contain xenoliths of eclogite, which is considered to be the high-pressure metamorphic product of basaltic oceanic crust, as it descends into the mantle along subduction zones.[7]
The large-scale inclusion of foreign rock strata at the margins of an igneous intrusion is called a roof pendant.
^Hansteen, Thor H; Troll, Valentin R (2003-02-14). "Oxygen isotope composition of xenoliths from the oceanic crust and volcanic edifice beneath Gran Canaria (Canary Islands): consequences for crustal contamination of ascending magmas". Chemical Geology. 193 (3): 181–193. Bibcode:2003ChGeo.193..181H. doi:10.1016/S0009-2541(02)00325-X. ISSN 0009-2541.
^Arakawa, Yoji; Endo, Daisuke; Ikehata, Kei; Oshika, Junya; Shinmura, Taro; Mori, Yasushi (2017-03-01). "Two types of gabbroic xenoliths from rhyolite dominated Niijima volcano, northern part of Izu-Bonin arc: petrological and geochemical constraints". Open Geosciences. 9 (1): 1–12. Bibcode:2017OGeo....9....1A. doi:10.1515/geo-2017-0001. ISSN 2391-5447.
^Troll, Valentin R.; Deegan, Frances M.; Jolis, Ester M.; Harris, Chris; Chadwick, Jane P.; Gertisser, Ralf; Schwarzkopf, Lothar M.; Borisova, Anastassia Y.; Bindeman, Ilya N.; Sumarti, Sri; Preece, Katie (2013-07-01). "Magmatic differentiation processes at Merapi Volcano: inclusion petrology and oxygen isotopes". Journal of Volcanology and Geothermal Research. Merapi eruption. 261: 38–49. Bibcode:2013JVGR..261...38T. doi:10.1016/j.jvolgeores.2012.11.001. ISSN 0377-0273.
^"Xenolith". Encyclopedic Entries. National Geographic Society. 2011. Retrieved 10 March 2018.
^Komov, I.L.; Lukashev, A.N.; Koplus, A.V. (1994). Geochemical Methods of Prospecting for Non-Metallic Minerals. Boca Raton: CRC Press. p. 32. ISBN 978-1-4665-6457-2.
^"Xenoliths in Meteorites". Science at LPI. Lunar and Planetary Institute. Retrieved 10 March 2018.
^Blatt, Harvey; Tracy, Robert (1996). Petrology: Igneous, Sedimentary, and Metamorphic (2nd ed.). W. H. Freeman. ISBN 0-7167-2438-3.
A xenolith ("foreign rock") is a rock fragment (country rock) that becomes enveloped in a larger rock during the latter's development and solidification...
and is the likely source rock for basaltic magma. It is found as rare xenoliths in basalt, such as those of Kilbourne Hole in southern New Mexico, US...
Universe Zero, Müller steals Xenolith's powers and body to create a replica of him for the Oración Seis Galáctica, forcing Xenolith to inhabit the body of a...
peridotite massifs, from fracture zones adjacent to mid-oceanic ridges, and as xenoliths in kimberlite pipes and alkali basalts. Partial melting of spinel lherzolite...
Mantle-peridotite xenolith from San Carlos Indian Reservation, Gila Co., Arizona, USA. The xenolith is dominated by green peridot olivine, together with...
mantle by examining mantle xenoliths brought up in kimberlite, lamproite, and other volcanic pipes. The histories of these xenoliths have been investigated...
surrounding rock as it explodes, bringing up unaltered xenoliths of peridotite to surface. These xenoliths provide valuable information to geologists about...
lamproite to phlogopite and olivine-rich tuffs. The chemistry of the mantle xenolith was used to derive maximum pressures of around 5 GPa and temperatures of...
2 km) south. Kilbourne Hole is notable for the large number of mantle xenoliths (solid fragments of mantle rock) that were carried to the surface by the...
on Papakolea Beach, Hawaii Light green olivine crystals in peridotite xenoliths in basalt from Arizona Olivine basalt from the Moon, collected in 1971...
greater than 0.708, suggesting a crustal origin. They also commonly contain xenoliths of metamorphosed sedimentary rock, and host tin ores. Their magmas are...
Durali, S.; Weyer, S. (2004). "Lithium isotopic signatures of peridotite xenoliths and isotopic fractionation at high temperature between olivine and pyroxenes"...
the volcanic tuff. Similar xenoliths have been found in the tuff of Surtsey and Heimaey. During eruptions these xenoliths were dislodged from eruption...
solid crystals of various minerals, fragments of exotic rocks known as xenoliths, and fragments of previously solidified lava. The crystal content of most...
found in mafic and ultramafic rocks occurring in lava and peridotite xenoliths of the mantle. The gem occurs in silica-deficient rocks such as volcanic...
chromium contents of enstatite in these xenoliths have been crucial in reconstructing the depths from which the xenoliths were plucked by the ascending magmas...
in a newer layer. A similar situation with igneous rocks occurs when xenoliths are found. These foreign bodies are picked up as magma or lava flows,...
mountain's numerous, cross-cutting felsic dikes. Embedded in the granite are xenoliths or pieces of foreign rocks entrained in the magma. The granite intruded...
granulite facies in the hot upper mantle. Many samples of eclogite are xenoliths brought to the surface by volcanic activity. Many orogenic belts contain...
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