Peridotite

Definition

Peridotite is a dense, coarse-grained igneous rock primarily composed of olivine, with lesser amounts of pyroxene and other minerals. It is significant as it represents the dominant rock type in the Earth's mantle and plays a crucial role in understanding mantle processes and the movement of isotopes within this deep layer of the Earth.

5 Must Know Facts For Your Next Test

1. Peridotite is primarily found in the upper mantle and can be exposed at the Earth's surface in areas known as ophiolites, providing direct evidence of mantle composition.
2. The mineral composition of peridotite varies depending on its formation conditions, but it typically contains over 40% olivine, which is crucial for understanding mantle dynamics.
3. Peridotite can also undergo partial melting to produce basaltic magmas, which are common at mid-ocean ridges and volcanic arcs.
4. Isotopic analysis of peridotite can reveal information about mantle processes such as melt extraction, subduction, and mixing of different mantle sources.
5. The study of peridotite is essential for understanding the thermal structure and chemical evolution of the Earth's mantle over geological time.

Review Questions

• How does the composition of peridotite contribute to our understanding of mantle dynamics?
  • The composition of peridotite, primarily rich in olivine, provides insights into the physical and chemical properties of the upper mantle. Since peridotite makes up a significant portion of the mantle, studying its mineralogy helps researchers understand processes like partial melting and melt extraction. The presence of different minerals within peridotite can also indicate variations in temperature and pressure conditions in the mantle.
• Discuss how peridotite relates to mantle convection and its implications for plate tectonics.
  • Peridotite's density and composition influence mantle convection patterns. The movement of this dense rock affects heat transfer within the Earth, driving convection currents that contribute to plate tectonics. As peridotite undergoes partial melting during convection, it produces basaltic magma that feeds into mid-ocean ridges and contributes to the creation of new oceanic crust.
• Evaluate the role of isotopic studies on peridotite in understanding Earth's geological history.
  • Isotopic studies on peridotite provide valuable data on the processes that have shaped the Earth's mantle over billions of years. By analyzing isotopic ratios, scientists can track changes related to melt extraction, subduction events, and interactions between different mantle reservoirs. This research helps reconstruct the thermal and compositional evolution of the mantle, providing a clearer picture of Earth's geological history and how it has influenced surface processes.

Related terms

Olivine: A magnesium iron silicate mineral that is a key component of peridotite and an important indicator of mantle composition.

Mantle Convection: The slow creeping motion of the mantle caused by convection currents, which is essential for understanding the dynamics of plate tectonics and heat transfer within the Earth.

Isotope Geochemistry: The study of the distribution and abundance of isotopes in geological materials, used to trace processes like mantle evolution, differentiation, and recycling.