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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.



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 ?
The sections demonstrate that the mapped surface PGE-enriched mineralization of the margin of the AN-Series, where the presence of magnetic basalt and sandstone xenoliths occur, has continuity at depth.
Xenoliths are rock fragments or inclusions that are torn from the sides of lava tubes and caught up in magma as it moves through Earth.
The xenolith rocks are slightly heavier on average, but their distribution of density overlaps that of the matrix.
The three additional representative samples reported upon, referenced as Matrix, Xenolith and ROM also continue to confirm and support the theory that most of the diamonds in this area are preferentially contained in the Xenolith portion of the rock outcrop.
6), with block structure comprising numerous xenoliths (up to ~100 m long) of pervasively recrystallised Unity anorthosite hosted by igneous-textured leucogabbronorite-leuconorite (Fig.
drilling,particularlythe discovery of a new mantle xenolith zoneadjacent
Hill and Ross (1983) concluded that the age of 238 [+ or -] 26 Ma obtained from a granulite xenolith represented the cooling age of the dyke, and is in close agreement with the 246 [+ or -] 4.
Some of them entrain deep crustal and mantle xenoliths to the surface, providing the only direct rock samples of the lithosphere available to us.
The nature of the subcontinental lithospheric mantle (SCLM) of the Slave is particularly well defined through geophysical and xenolith data.
The DFI drill program is targeting geophysical anomalies which may represent the massive sulphide body from which the Homse xenolith has been torn.
Compositional gradients in xenolith olivine adjacent to type 2 glass pools and jacket glass can be modelled as Fe-Mg interdiffusion profiles tbat indicate melt -- olivine contact times between 0.
Experimental high-pressure granulites: Some applications to natural mafic xenolith suites and Archean granulite terranes.