Interior of the Earth and planets is one of the most important targets for the high pressure research. In this paper, gross pictures on the layered structure, chemical compositions, and the pressure and temperature conditions of the Earth interior are presented. Some topics on the high pressure research relevant to the Earth interior are also reviewed.
The author reviews the phase transformations in the earth's mantle, which have been determined by using latest multi-anvil technology. The composition and constitution of the mantle are discussed on the basis of these phase equilibrium data, together with other data sets from laboratory measurements and seismic observations. The phase transformations in a pyrolite composition satisfactorily explain the gross nature of the seismic velocity/density profiles throughout the mantle. Thus pyrolite is considered to be a representative mantle composition. Further detailed seismic velocity structures in the mantle are also discussed in terms of the phase transformations in other compositions comprising subducted slabs.
This paper reviews the important improvements accomplished during the past thirty years in the application field of the diamond anvil cell to high pressure single crystal X-ray structure analysis . The characteristics of the single crystal high pressure method are reviewed in Sec. 2. The implications of the single crystal structural analysis at high pressure are discussed for the case of structural anomalies of forsterite, Mg2SiO4 and fayalite, Fe2SiO4 under metastable condition with over-pressure inSec. 3.
In the last decade, reaction of metals and silicate minerals under high pressure and temperature have been studied extensively. These investigations have revealed that the solubility of hydrogen, oxygen and silicon in metallic iron are enhanced by high pressure, and these elements were added to the candidates of the light elements in the earth's core. Pressure effect on partition coefficients of elements between metallic iron and mantle minerals have also been examined by high pressure experiments. These experimental investigations have successively provided important information for the studies of formation and composition of the earth's core. Some difficulties, however, still remain in the high pressure experimental techniques for metal-mineral reaction, such as the reaction of the sample and its container.
Knowledge of the structural changes of silicate melts under high pressure and temperature is extremely important to understand the chemical and physical properties of magmas in nature. In-situ x-ray measurements are possible for silicate melts under high pressure by means of synchrotron radiations and multi-anvil apparatus (MAX80). It is, however, difficult to obtain corrected x-ray intensity profiles because of the source intensity profile, absorption, incoherent scattering, etc. Observed intensity of melts can be corrected reasonably by means of a Mote Carlo simulation technique.
Current status on the development of a high pressure and high temperature in situ x-ray diffraction technique is reviewed. Combination of new apparatuses with sintered diamond anvils and a very strong x-ray beam from a synchrotron source made it possible to carry out an in situ x-ray study on mantle minerals under lower mantle conditions (≥24 GPa, 1900 K). Important information for understanding the nature of the solid earth will be obtained by these apparatuses.
A new quantitative laser-heated diamond anvil cell has been developed. The systems for the measurements of pressure and temperature are also constructed. Pressures under high temperature can be measured using Sm: YAG pressure marker. The other technical improvements are described in detail. Several phase equilibrium experiments of silicates are carried out using the system. The upper-lower mantle boundary is also discussed on the basis of determined spinel dissociation boundary.
The MA8 system can generate relatively uniform pressure and get a large sample volume to including heating system. As an anvil material we have employed tungsten carbide. However, the efficiency of high pressure generation above 20 GPa is reduced because of plastic deformation of anvil top. Sintered diamond which has the highest compressive strength and no cleavage plane is the most promising choice as the alternative for anvil material. The purpose of this study is to develop the high pressure apparatus with sintered diamond anvils including internal heating capable under ultra high pressures and to establish condition for the reliable experiments. In this system we succeed in generating pressures over 30 GPa and temperature about 2000°C in a sample volume of about 1mm3. We confirmed of decomposition of forstrite to perovskite and periclace by X-ray diffraction analysis. This new high pressure system must be useful for quantitative studies to investigate the physical and chemical properties in the earth's deep interior.
High pressure studies on planetary materials provide very important contributions for the understanding of the internal structure of the planets, since the knowledge of the properties of the high pressure phases of the planet forming materials gives constraints for discussing the internal structure of the planets. Here is reviewed the internal structure of planets inferred from the high pressure research together with geophysical and geochemical observations.
Pressure effect on the diffusion of rigid aromatic and flexible linear aliphatic molecules in polymers was described. The results were discussed on the basis of the activation volume for the diffusion, ΔV≠. ΔV≠ was analysed in terms of the intrinsic molecular volume, the length of the chain, the degrees of swelling and crystallinity of the polymer and the solvation of the diffusant. The temperature dependence of. ΔV≠, the pressure dependence of the activation energy for the diffusion and the pressure dependence of de Genne's scaling rule for the diffusion of chain molecule were also discussed.
Method of pressure measurement by ruby fluorescence in a diamond-anvil cell at relatively lower pressure is described. Anisotropy of sensing ruby fluorescence and its effect for the accurate pressure measurement are also discussed. Non-hydrostaticity is estimated by the fluorescence of two rubies which have different crystal orientations. Annealing of sensing ruby is effective for improving the accuracy of pressure measurement.