透辉石-钙长石体系熔体在不同过冷条件下晶体生长研究

CRYSTAL GROWTH OF DIOPSIDE-ANORTHITE MELTING SYSTEM UNDER DIFFERENT UNDERCOOLING CONDITION

实验以透辉石-钙长石二元体系在不同过冷度下形成的透辉石晶体为研究对象,通过光学显微镜、X射线衍射、电子探针、透射电镜等手段进行分析,结果表明在透辉石生长边界发现存在过渡层的特点;透辉石晶体的形貌、成分、结构随着过冷度的增大都发生了明显的变化。随着过冷度的增大,晶体的自形程度逐渐降低,从自形、半自形向骸晶、枝晶变化;在透辉石硅氧骨干中,铝硅比值增大,铝代替镁形成[AlO6]八面体也增多,从而使透辉石的晶胞参数a,b呈减小趋势;c呈增大趋势。

Effect of different undercooling degrees on the crystallization behavior of diopside （Di）-anorthite （An） binary system was studied by optical microscope,X-ray diffraction, Raman spectroscopy,electron probe microanalysis and transmission electron microscope. Results showed that there was a transitional layer between the crystal growth frontier and melt. The morphologies,composition and structure of the diopside crystal were systematical changed under different undercooling degrees. As the undercooling degree was increased,the crystal integralities of dioposide decreased gradually from idiomorphic, half-idiomorphic to skeletal and dendritic. The lattice parameters a,b of diopside tended to decrease and c increase. The larger the undereooling degree was, the more Al^3＋ replaced Si^4＋ in [ SiO4 ] and the more Al^3＋ replaced Mg^2＋ in [ MgO6].