| 其他摘要 | Pressure-volume-temperature equation of state of minerals is the research on the relationship among cell volume, temperature and pressure of minerals under certain temperature and pressure. Based on this relationship, we can learn the density, elasticity and thermal expansion of minerals under certain temperature and pressure. The research of PVT equation of state of minerals can help us to understand the state of minerals in the Earth's interior, and can provides a basic data for further theoretical calculation. The results of the PVT equation of state of minerals can also be compared with the inversion of the natural and artificial seismic waves, and help us to understand the geological process, material structure and composition of Earth's interior. However, up to now, the PVT equation of state studies are focused on oxide minerals, the major minerals of upper mantle (olivine and pyroxene) and their high pressure phases (wadsleyit, ringwoodite magnesio-wüstite, majorite, Mg-perovskite, Ca-perovskite). There are very little PVT equation of state researches concerning the accessory minerals of upper mantle (garnet, spinel) and sulfide minerals.
The author participated in the construction of the outside heating system of the diamond anvil cell and improved it. And on the basis of the outside heating system of the diamond anvil cell device and in situ high temperature and high pressure energy dispersive and angle dispersive X-ray diffractions source, author studied the PVT equation of state of natural almandine, spessartine, chromium spinel, and sphalerite, cinnabar, galenite, molybdenite, stibnite. According to the results of those studies, combined with previous experimental datas, we discussed the effect of the isomorphous substitution on the equation of state in the pyrope-almandine, spessartine-almandine, and spinel. In addition, we also analyzed the effect of the isomorphous substitution on the phase transition and equation of state in sulfide mineral. The experimental results show that:
1. The bulk modulus of pyrope-almandine and spessartine-almandine increases with the composition of almandine increasing. From the subsequent analysis, the Fe2+-Mg2+ and Fe2+-Mn2+ substitution in bivalent ion site is the main factor. For pyrope-almandine, the comparison of the Fe2+ covalent radius (1.17Å) in almandine and the Mg2+ (1.36Å) in pyrope has relatively larger covalent radius. Furthermore, the bond length of Mg2+-O (2.270Å) in pyrope and the bond length of Fe2+-O (2.299Å) in almandine are similar. For spessartine-almandine, the Mn2+ covalent radius (1.17Å) of spessartine is equal to the Fe2+ covalent radius (1.17Å) of almandine, but the Mn2+-O (2.326Å) in spessartine is larger than the bond length of Fe2+-O (2.299Å) in almandine. A smaller covalent radius and bond length can enhance the binding force between ions, enhancing anti-compression capacity of material, thereby, increasing the material's elastic modulus. Therefore, the bulk moduli of pyrope-almandine and spessartine-almandine increase with the increasing of almandine composition.
2. The temperature derivative of the bulk modulus of chromium spinel ((Mg0.6766Fe0.2808Na0.0073Ti0.0014)0.9661(Cr1.4874Al0.5367)2.0241O4) is obtained for the first time. A comparison of the elastic parameters in this work and previous results reveals that the responsibility for bulk modulus of Fe2+-Mg2+ substitution in tetrahedral site is more than Cr3+-Al3+ substitution in octahedral site. And the main factor of the relatively large bulk modulus of the natural chromium spinel is the substitution of Fe2+ to Mg2+ in the tetrahedral site.
3. According to the PVT equation of state of spinel and garnet, we calculated the change of the density of different components of pyrolite under different temperature and pressure conditions of the upper mantle. The results show that the change of components of spinel (2%－10%) can result in the large difference of densities in spinel iherzolite (2.2%). In garnet iherzolite (garnet: 14%－20%) and eclogite (garnet: 37%－45%), the change of components of garnet have resulted in little change of density, because garnet is an important components in the garnet iherzolite and eclogite.
4. The temperature derivative of the bulk modulus and thermal expansivity coefficient of cinnabar phase of cinnabar, B33 phase of galena, molybdenite, and stibnite are obtained for the first time. We also discussed the phase change of the sphalerite, cinnabar, and galena.
5. Summarized the phase change of zinc chalcogenides, mercury chalcogenides and lead chalcogenides. The reason of the phase transition pressure of zinc chalcogenide, mercury chalcogenide, lead chalcogenide decreases with the increasing of anion atomic number(S→Se→Te) is that the relatively larger atomic number in the same group of the periodic table has a larger number of core electrons, so that the effective potential for the valence and conduction electrons becomes weaker, leading to the ionization energy of the conduction electrons for the heavier atom, therefore, the phase transition can occur in lower pressure.
6. The author analyzes the effects of anions and cations of Zn0.76Fe0.23S, Sb2S3-Bi2S3, MoS2-WS2 and the different composition of simple sulfide mineral with the same structure on the elastic modulus. The elastic modulus of the simple sulfide mineral depend on the the ionic radius, electronegativity and bond length between anion and cation. |
修改评论