热历史差异对硅酸盐熔体结构状态及其结晶行为的影响

It is difficult to experimentally study the silicate melt structure since the high temperature and long-range disorder of the melts. In this project, we have investigated the variation of silicate melt structure with the thermal history of Ab-An-Di ternary system near the liquidus temperature. The effects of melt composition and structure on the crystallization were also studied. The changes of structural species and relative abundance in melts and glasses with cooling rates were analyzed carefully. It is shown from the experiments that the silicate melt structure and composition can control the behavior of crystallization, meanwhile the structure of crystal can heritage the structural characteristic of melt. The growth units of silicate crystals are mainly the segments of Si-O polymer with different polymerization degree. In high-temperature Raman experiments, one kind of melt structure transform, from short-range to medium-range, was found in the melt whose composition is in basaltic magma region. This means that phase separation, or immiscible, occurred in the high temperature melt state, which there is important application in magmatic process. With series of researches on crystallization by melt cooling, we have obtained plenty of results of the relationship between morphologies and crystal structures and melt structure and cooling rates. Dendritic diopside and spherulitic plagioclase, which were formed in the exactly same cooling conditions, are consistent with the argument that the anisotropy is a crucial factor in crystal growth. From the relatively simple silicate system, the results indicate that the relatively concentration of structural species vary with the cooling rates.

通过高温实验及其淬冷样品的物相结构检测，研究Ab-An-Di系统随热历史变化而导致的硅酸盐熔体结构状态相应调整改变和结晶行为改变的规律。详细分析降温速率、保温温度和时间如何影响熔体的结构单元种属、相对数量和连接方式。查明熔体结构与结晶行为的内在联系和相互制约关系。由此揭示岩浆作用过程细节，以及指导有关材料生产的工艺设计。