| During the developing of crystal growth study, more attention had been paid to the growth under equilibrium and near equilibrium, but it's opposite to disequilibrium growth. In the fact, crystal growth is a disequilibrium process. So it's practical to study crystal growth under disequilibrium state. And it attracted more and more Scientists' interests.Dentrite is a kind of crystal with branched morphology. Initially, it's referred to branch structure in metal casting ingoting. It grows far from equilibrium and exists universally in micro-texture of metallurgical industry materials, ceramic materials and volcanic rocks, even in organic texture reported recently. Relating to many various science fields such as petrology, crystallography, materials science and fractal science, that study of dentrite is of great significance to theory and utility.From 19th century to today, many scientists have done lots of research. Those works are mainly about dentrite in metal and alloy materials. Some are about un-metal materials. Less about dentrite of silicate melts in earth science field.In this paper, we choose Diopside-Albite-Anorthite (Di-Ab-An) this silicate system as the study subject. Let crystals grow fast with different cooling-rate to format dentrites. We set eight samples worth researching ,by means of cross polarized light microscope, back electron image' electron probe microanalysis, x-ray powder crystal diffraction analysis and laser Raman spectrum analysis, discussed regular evolution of the morphology, composition, crystal structure dentrite samples formatted under different cooling-rate. So we can make following conclusions:1. In cooling temperature range: 1350℃-800℃, when cooling-rate ﹥10℃/minute, it's too fast to crystallize, the samples are transparent glass matter without crystal blocks in eye sight. Objected under micropolariscope, the samples are all glass matrix no small crystal piece in it; when cooling-rate = 10℃/minute, the samples are transparent glass matter without crystal blocks in eye sight. Objected under micropolariscope, there are less small crystal pieces in glass matrix; when cooling-rate ﹤10℃/minute(5℃/minute,3℃/minute,1℃/minute), the samples partly crystallized. Crystal blocks are white and untransparent, grew from the ball sample outside to inside; when cooling-rate = 1℃/minute, the samples all crystallized. The samples, with the same composition point and cooling-rate, the crystal amount of big one is less than that of the smaller one.2. Dentrites of sample 1-6,1-8,1-7 are diopside. Dentrites of sample 4-6,4-8,4-7 are plagioclase, in which exist less diopside. Comparing the samples' x-ray diffraction pattern and that of all plagioclase end members', we consider the dentrites of samples 4-6,4-8,4-7 are labradorite.3. Different phase dentrite morphologies vary much from each other. The morphologies of diopside dentrites of sample 1-6,1-8,1-7 are feather-like or branch-like, first branches regularly assembling side of the main branch, some present secondary branches; Those of sample 4-6,4-8,4-7 are radial fiber-like or assembled-needle-like, without branch structure4. Cooling-rate also influences the dentrite morphologies. When cooling-rate≦5℃/minute, for the same composition point samples, the lower the cooling-rate was, the slender the branches were, and the morphology changed more complex. But it only changed detail parts.5. For diopside dentrite, when the cooling-rate increased, much more Al displased Si got into the silica tetrahedron [SiO4] (the atomic coefficient of Al in [SiO4] changed: 0.08 ? 0.12 ?0.17); less Al displaced Mg got into the coordination octahedron (the atomic coefficient of Al in the coordination octahedron changed: 0.42 ? 0.37 ?0.18). In glass matrix, Al did not displaced Si in [SiO4]. It's hexad coordination.6. For plagioclase dentrite, all Al got into [SiO4], displaced Si partly. And the larger the cooling-rate was, the more Al displaced Si (the atomic coefficient of Al in [SiO4] changed: 1.20?1.21 ?1.37). It's the...
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