Mantle nodule (xenolith) mineral assemblages as indicators of depth of derivation (plagioclase-, spinel-, and garnet-peridotite facies).
Mantle peridotite mineralogy changes systematically with depth/pressure: at shallow depths, plagioclase is the stable aluminous phase (plagioclase peridotite); at intermediate depths, spinel is stable instead...
Full option-by-option analysis available to enrolled students.