| Such rocks are important in defining ages for crustal rocks underlying the peridotite. |
| The formation and preservation of the peridotite mylonite in particular presents problems of interpretation. |
| Dolerite dykes that cut the peridotite show chilled margins and local metasomatic calcic alteration. |
| The mantle is thought to be made up mostly of peridotite, a type of rock composed of iron, magnesium, silicon, and oxygen. |
| Its lower part displays alternating bands of peridotite, pyroxenite, and dunite, but dunite is dominant throughout most of the unit. |
| It is clear nevertheless that transforms are sites where deep-seated rocks, such as serpentinized peridotite, are relatively common. |
