The mechanism of reaction in MgO-SiO₂ and MgO-SiO₂-CaO systems is investigated in this paper. The following two series of experiments have been practiced; 1) Mixture of MgO powder (99.9%) and quartz grains (99.99%, 150-300 μm), and 2) Mixture of MgO powder, quartz grains and additional 0.4% of CaO were heated at the temperatures between 1400°C and 1600°C. In MgO-SiO₂ system, Mg²⁺ ion diffused into quartz grains to form reaction layers of forsterite and thin layers of enstatite when heated below 1500°C. When the sample was heated above the eutectic temperature (1543°C) of the system, forsterite was observed on both sides of quartz and sintered MgO. These facts suggest that the liquid, which is formed in between enstatite and quartz, penetrates through forsterite into sintered MgO. As the result, SiO₂ component removes from quartz and then gaps or pores are formed in quartz grains. Finally quartz grains are replaced the vacant pores. In MgO-SiO₂-CaO system, forsterite was observed inside sintered MgO and an opening of gaps in quartz grains begins at a temperature as low as 1400°C. This suggests the liquid phase occures at the temperature as low as 1400°C when the third component, CaO, is added. The phases supposed to be liquid in the reaction layers were analysed EP-MA. The fact that the analysed data roughly coincide with the composition of ternary eutectic liquid will strongly support the above assumption.

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This review presents a recent progress in theoretical analysis of non-equilibrium textures in rocks. Classical irreversible thermodynamics provides a powerful tool for the analysis in a linear non-equilibrium regime not far from equilibrium. First we discuss the rate-determining processes and resulting non-equilibrium textures based on Fisher's method. This analysis clarifies the relationship between three rate-determining processes: the diffusion-controlled, the reaction-controlled, and the heat-flow-controlled processes in metamorphism. Discussions extends into characteristics of various non-equilibrium textures such as reaction zones, composite veins, oscillatory zoning, comb layering, and metamorphic layering. Strategies for the analysis of these non-equilibrium textures and what informations we can get from them are also discussed. Finally, the most successful method for the analysis of diffusion-controlled structures developed by Fisher and Joesten, the steady diffusion model, is explained in detail, and the application to a natural example, an olivine-plagioclase corona, by Nishiyama is summarized. Steady state coupling of diffusional fluxes and chemical reactions at the layer contacts reduces to mass balance relationships having phenomenological coefficients' ratios as unknown parameters. The parameters control the stability of zonal arrangements and also determine the exchange relationships of diffusing components between mineral layers.

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An X-ray diffractometer newly designed for thin film analyses is consisted of a compact X-ray generator with high loaded power rate to a small focus, a curved position sensitive detector and K-axis type 4-circle goniometer. The diffractometer enables measurements of thin film samples for electronic devices, e.g. rapid pole figure measurements of thin film samples and depth-sensitive measurements of multilayer thin films. A preffered orientation analysis of Co-Nb-Zr films for VTR core and a crystallinity analysis of multilayer films for circuit board were performed by using this apparatus.

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