A xenolith ("foreign stone") is a rock fragment encased in larger rocks during the last development and compaction. In geology, the term xenolith is almost exclusively used to describe inclusions in igneous rocks during magma and eruption emplacement. Xenolith can be swallowed along the edges of the magma chamber, regardless of the eruption or diatreme exploding lava channel walls or raised along the base of the lava that flows on the Earth's surface. A xenocryst is an alien crystal of individuals belonging to a frozen body. Examples of xenocrysts are quartz crystals in silica-deprived lava and diamonds in kimberlite diatremes. Xenoliths may not be uniform in individual locations, even in areas that are spatially limited, eg. the dominant Rhino-dominated lava volcano (Japan) contains two types of gabbroic xenoliths originating from different sources - they are formed in different temperatures and pressures.
Although the term xenolith is most commonly associated with frozen inclusions, a broad definition may include rock fragments that have been encased in sedimentary rocks. Xenolith is sometimes found in meteorites that are found.
To be regarded as true xenoliths, the included rocks must be identifiable differently from the rocks in which they are enveloped; rocks belonging to the same type are called autolith or cognate inclusions.
Xenolith and xenocrysts provide important information about the composition of the mantle that is not accessible. Basalt, kimberlites, lamproites and lamprophyres, which have their source in the upper mantle, often contain fragments and crystals that are considered part of the mineralogy of the mantle of origin. Xenoliths dunite, peridotite and spinel lherzolite in basaltic lava flows are one such example. Kimberlites contain, in addition to diamond xenocrysts, lherzolite fragments of various compositions. Aluminum-containing minerals from these fragments give a hint of the depth of origin. Plagioclase calcium is stable to a depth of 25 km (16 mi). Between 25 km (16 mi) and about 60 km (37 mi), the spinel is a stable aluminum phase. At a depth of more than 60 km, solid garnet becomes a mineral containing aluminum. Some kimberlites contain eclogite xenoliths, which are considered to be high-pressure metamorphic products of the basaltic oceanic crust, as they fall into the mantle along the subduction zone.
The entry of large-scale strata of foreign rocks in the frozen intrusive rock margins is called roof pendant .
Video Xenolith
Example
Maps Xenolith
References
- Nixon, Peter H. (1987). Mantle Xenoliths . J. Wiley & amp; Children. ISBNÃ, 0-471-91209-3.
External links
Source of the article : Wikipedia
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