Thermal changes of synthesized rare earth phosphates were studied at 50°C to 1800°C in air under atmospheric pressure or the pressure of 7.5 to 12.5 GPa. 1) Rhabdophane-type RPO₄·nH₂O (n=0.5 to 1.0, R=La-Gd, Tb, Dy, Y, Er, or R=Ce+Y) were synthesized by precipitation from the mixed solution of R-salt and orthophosphoric acid at 50°C or 90°C and pH=1, or by grinding weinschenkite-type RPO₄·2H₂O (R=Dy, Y, or Er) at room temperature for 10 days. Rhabdophane-type phosphates were dehydrated at 190°C to 250°C. The water corresponding to nH₂O was zeolitic water. Thermal changes of rhabdophane-type anhydrous RPO₄, when heated in air under atmospheric pressure, were as follows : (1) rhabdophane-type RPO₄ (R=La-Gd, or R=Ce+Y)→monazite, (2) rhabdophane-type RPO₄ (R=Tb or Dy)→monazite→xenotime, (3) rhabdophane-type RPO₄ (R=Y or Er)→xenotime. The transformation from monazite into xenotime (2) was monotropic when heated in air under atmospheric pressure. Xenotime-type DyPO₄, however, transformed into monazite-type DyPO₄ when heated at 650°C to 1000°C in air under the pressure of 7.5 to 12.5 GPa. 2) Weinschenkite-type RPO₄·2H₂O (R=Dy, Y, Er, or Yb) were synthesized by precipitation from the mixed solution of R-salt and orthophosphoric acid at 50°C and pH=1. Weinschenkitetype RPO₄·2H₂O gradually converted to xenotime when heated in air under atmosheric pressure.

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Heulandite was synthesized without any natural seed from amorphous solids of the clinoptilolite-epistilbite system which consists of the Na₃K₃Al₆Si₃₀O₇₂·Aq-Ca_4.5Al₉Si₂₇O₇₂·Aq join (CE subsystem) and the Na_2.9K_2.9Al_5.8Si_30.2O₇₂·Aq-Ca_4.8Al_9.6Si_26.4O₇₂·Aq join (CW subsystem). At PH₂o=1, 000 bars and reaction time =50 days, heulandite was formed as a single phase in the temperature range lower than 275°C and mordenite and analcime (or wairakite) coexisted with heulandite in the range from 275 to 295°C. The compositional range of the synthesized heulandites is Si/Al=3-4 and Ca/(Ca+NaK)=0.5-0.9, and these ranges are not contradictory to those of natural heulandites. The results of heating treatment and DTA of the synthesized heulandites indicate that their thermal stability increases gradually with increasing Si and NaK contents. The relation between chemical composition and thermal behavior of the synthetic heulandites is similar to that of natural heulandites, but a synthetic heulandite of the CE3 composition which is included in the compositional range of heulandite type 2 shows the thermal behavior close to heulandite type 1.

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A review is given of how the characteristics in plastic flow of a crystal observed on a macroscopic scale are understood in terms of dynamic processes of dislocations which take place on a microscopic scale inside it. Theoretical treatments are developed quantitatively for various dislocation processes which play important roles in determining the deformation characteristics in the case of a silicon crystal. The stressstrain curve is derived theoretically as a function of temperature, strain-rate and density of dislocations initially included in the crystal on the basis of dynamic characteristics of dislocations which have been clarified by experimental observations. It is demonstrated that a good agreement is obtained between theoretically derived stress-strain behavior and experimentally observed one.

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Plastic deformation experiments of major silicate minerals are reviewed with focussing on what have been aimed and what have been clarified in those experiments. The experiments include those of uniaxial compression, three-point bending and indentation creep. Some systematic relationships between high-temperature plasticity and crystal structure are also discussed.

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Deformation textures (i. e. fracturing, plastic deformation, recrystallization, vitrification, phase transforma-tion, and melting) in naturally and artificially shocked mineral crystals have been reported. The main part of this report is devoted to a description of the shock-induced residual effects in olivine and orthopyroxene crystals recovered from shock experiments by transmission electron microscopic observation. Deformation textures in naturally shocked olivine crystals from some meteorites were also described.

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This century is the century of plate tectonics, and its last decade should be devoted to the establishment of plate dynamics. This note summarizes the current status of rock rheology in the quantitative evaluation of the plate interaction across large-scale faults and transform-type plate boundaries. S-C mylonites and ultramylonites are likely to have formed in the strength-peak regime. These rocks, together with pseudo-tachylytes, are perhaps the most crucial rocks to evaluate the forces acting on two plates sliding each other. It is hoped that complete deformation mechanisms in these rocks will be analyzed fully by miner-alogists so their rheological properties can be explored realistically through laboratory experiments.

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Rheology of the Earth's crust and mantle is simulated by the plastic behaviour of the polycrystalline quartz and plagioclase, olivine, spinel and perovskite, respectively. To infer the dynamics of the Earth's interior reaching the core-mantle boundary, it needs to study the constitutive flow laws and preferred lattice orientation formation of these crustal and mantle materials. The aim of this paper is to review the recent development of the rheological study of these processes and to add the new constraints on the seismically anisotropic convective mantle.

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Chondrites were formed in small planets, where convection did not occur Therefore, rheological processes such as bracciation and shock deformation were essential in the formation of parent bodies of chondrites. Origin of chondrules were also reviewed with reference of shock melting.

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