A xenolith is best described as which of the following?

A xenolith is best described as a type of igneous rock clast, which refers to a fragment of rock that becomes incorporated into another rock during the formation of the latter. Specifically, in the context of igneous rocks, xenoliths are pieces of rock that are enclosed within an igneous body as it intrudes into the surrounding rock. The term "xenolith" literally means "foreign rock," highlighting that these fragments originate from a source different from that of the surrounding igneous material. This can provide valuable information about the composition and conditions of the Earth's crust from which the xenolith originated.

In geology, understanding xenoliths can be crucial for interpreting geological processes, as they reveal insights into the thermal and chemical history of the Earth's lithosphere. The other choices do not align with the definition of xenoliths—sedimentary rocks are formed from the accumulation of sediment, fossilized trees pertain to paleontology, and mineral deposits generally refer to concentrated accumulations of minerals rather than fragments of rock.