Mantle xenolith

A fragment of mantle rock transported to the surface inside ascending magma. Its minerals and chemistry provide samples of Earth’s otherwise inaccessible mantle.

Earth's mantle: The thick rocky layer between Earth's crust and core, extending to a depth of about 2,900 kilometers. These fragments originate within this layer and provide direct samples of it.
Xenolith: A fragment of pre-existing rock enclosed within a different host rock. Mantle xenoliths are the deep-source subset of this broader geological category.
Geothermobarometry: Methods that estimate the temperature and pressure at which minerals or rocks equilibrated. Mineral assemblages in xenoliths can constrain their mantle depth and temperature.
San Carlos xenoliths: Peridotite xenoliths from the San Carlos volcanic field in Arizona, widely used in mantle studies. Their well-studied minerals provide a reference for interpreting upper-mantle peridotite.
Peridotite: A coarse-grained ultramafic rock composed mainly of olivine and pyroxene. It is the most common rock type represented by upper-mantle xenoliths.
Magma: Molten or partially molten rock beneath Earth's surface, containing crystals and dissolved gases. Ascending magma transports mantle fragments through the crust.
Mantle metasomatism: Chemical modification of mantle rock by fluids or melts moving through it. Mineral and chemical variations in xenoliths reveal this overprinting of mantle rocks.
Kaapvaal craton: An ancient, stable region of continental crust and mantle in southern Africa. Its kimberlites carry xenoliths that sample a thick, long-lived mantle root.
Olivine: A magnesium- and iron-bearing silicate mineral common in Earth's mantle and many igneous rocks. Its composition in xenoliths helps estimate the conditions and chemistry of the mantle.
Volcanic conduit: A passage through which magma moves toward or reaches Earth's surface. Fragments can be carried upward through conduits during an eruption.

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