This book provides an analysis of an actual problem of the evolution of deep matter under the conditions of the upper mantle, transition zone, and uppermost lower mantle. This issue has a fundamental importance in geochemistry, petrology, mineralogy, and crystalochemistry of the mantle, at different depths. The authors discuss new experimental research on the composition and conditions of the chromium-bearing minerals genesis and their associations in the Earth's mantle. The experimental data are compared with the natural mineral assemblages, allowing a refinement of the structure and composition of the deep Geospheres of the Earth. The results of the physicochemical experiments in the "MgO-SiO2-Cr2O3" model and the multicomponent systems play a major role in understanding the phase diagrams of these systems, the structural patterns of chromium-bearing phases and the influence of Cr on P-T parameters in the Earth's mantle.

Contenu
INTRODUCTION
PART I. Chromium and chromium-bearing phases in the EarthChapter 1.1. High-pressure Cr-bearing phases in the Earth's mantle1.1.1. (Mg,Fe)Cr2O4 polymorphs1.1.2. Majoritic and knorringitic garnets1.1.3. Clinopyroxenes1.1.4. (Mg,Fe)2SiO4 polymorphs1.1.5. (Mg,Fe)SiO3 polymorphs1.1.6. Other Cr-bearing phases in the Earth's mantleChapter 1.2. Cr-rich rocks and mechanisms of Cr concentration in the Earth's mantle
PART II. Experimental study of Cr-bearing phases at high pressuresChapter 2.1. Experimental and analytical techniques2.1.1. Multi-anvil apparatus2.1.2. Toroidal (anvil-with-hole) apparatus2.1.3. Analytical procedureChapter 2.2. Review of the experimental data2.2.1. Systems with high-pressure components of garnets2.2.2. Influence of Cr and other minor elements on Mg2SiO4 polymorphsChapter 2.3. Experimental study of the model system SiO2-MgO-Cr2O3 at high P-T parameters2.3.1. Mg4Si4O12-Mg3Cr2Si3O12 section at 10-24 GPa and 1600CPhase relationsCompositions of the phasesTopology and phase diagram of the Mg4Si4O12-Mg3Cr2Si3O12 psedo-section2.3.2. Mg2SiO4-MgCr2O4 section at 10-24 GPa and 1600CPhase relationsCompositions of the phasesTopology and phase diagram of the Mg2SiO4-MgCr2O4 psedo-sectionChapter 2.4. Experimental study of multicomponent systems with Cr-bearing phases at high P-T parameters2.4.1. Influence of minor Al concentrations on crystallization of garnet in the majorite-knorringite system2.4.2. Crystallization of knorringitic garnet in the pyrolite systemChapter 2.5. Structural patterns of Cr-bearing phases
PART III. Implication of experimental results to geochemistry of Cr in the Earth's mantleChapter 3.1. Mineral hosts for CrChapter 3.2. Influence of Cr on structural pattern of the major mantle phases