A xenolith is a fragment of rock that is enclosed within a larger body of igneous rock, typically carried to the surface by volcanic eruptions. Xenoliths are significant in petrology for providing information about the composition and conditions of the Earth’s mantle and lower crust, offering insights into deep geological processes.
Reference: Gillet, P., McMillan, P., & Guyot, F. (1992). “Thermodynamic Properties and Geophysical Applications of Xenoliths.” Nature, 357(6374), 164-168.