This book presents the first overview of the composition and structure of the Earth's lower mantle. The first part focuses on the study of lower-mantle minerals, identified as inclusions in diamonds from different regions of the world. Three associations are established among the lower-mantle minerals: ultramafic, mafic, and carbonatic. The carbonatic association is of particular interest because it characterizes the media of natural diamond formation. In turn, the second part analyzes the structure of the lower mantle, revealing its heterogeneous composition. It is based on the results of experiments demonstrating phase transitions in lower-mantle minerals, and on seismological data. Deep-seated earthquakes point to the presence within the lower mantle of numerous seismic boundaries caused by mineral structure transitions. In closing, the last part of the book compares observed data with experimental data, highlighting several discrepancies that indicate Earth may have a more complex planetary history than previously assumed, and examining its primarily non-chondritic composition.
Presents the first comprehensive overview of the composition and structure of the Earth's lower mantle
Introduction: History of the problem1. Models of the Earth's mantle2. High-pressure experimental data on ultramafic and mafic systems3. Natural lower-mantle minerals 3.1. General 3.2. Ultramafic association 3.3. Mafic association 3.4. Carbonatitic association4. Lower-mantle mineral associations 4.1. Ultramafic 4.2. Mafic 4.3. Carbonatitic association, its origin and role in the formation of diamond5. Some problems in the mineral composition of the lower mantle6. Iron spin crossover in lower mantle minerals 6.1. (Mg,Fe)O 6.2. Bridgmanite 6.3. Distribution of iron between (Mg,Fe)O and bridgmanite: theoretical constructions, experiments and natural compositions7. Phase transitions in lower-mantle minerals 7.1. Bridgmanite 7.2. CaSi-perovskite 7.3. (Mg,Fe)O 7.4. SiO2 7.5. Other minerals8. Crystallographic features (regularities) of lower-mantle mineral phases 9. Changes in properties of chemical elements under high pressures and possible new mineral compounds in Deep Earth10. Seismic inhomogeneities in the lower mantle and their nature11. Local inhomogeneities in the lower mantle12. Geochemistry of the lower mantle 12.1. General composition of the lower mantle 12.2. Trace element geochemistry 12.3. Volatiles in the lower mantle 12.4. Isotopic characteristics of carbon, oxygen and nitrogen in the lower mantle13. Oxidation potential in the lower mantle14. D" layer: transition from the lower mantle to the Earth's core. (Postperovskite and other minerals in the D" layer) 15. Conclusions. Compositional model of the lower mantle. Further problems ReferencesSubject index