THE STRUCTURES AND PHYSICAL PROPERTIES OF MAGMAS

利用长石和火山玻璃的结构分析了高温高压条件下岩浆的结构和物理性质。a)用X射线衍射和拉曼光谱分析了SiO_2玻璃的冲击波致密化。用立方压力机在500℃/4 Gpa和7.7 Gpa的压力下对长石(NaAlSi_3O_8 CaAl_2Si_2O_8)玻璃进行了压缩。用拉曼光谱对玻璃的结构进行了分析。结果表明，在高温高压条件下，斜长石玻璃的结构具有较小的To4四面体环状结构，Al原子的配位数从4变化到6。同时对CaAl_2Si_2O_8玻璃进行了冲击实验，发现密度的增加幅度小于SiO_2玻璃的密度增加幅度，这是由于CaAl_2Si_2O_8玻璃中TO_4四面体三元环的增加所致。用原位拉曼光谱研究了激波去屏蔽CaAl_2Si_2O_8玻璃的退火过程。这些结果对于了解含铝岩浆是非常重要的。c)用X射线衍射和拉曼光谱技术研究了冲击和静态压缩获得的致密化火山玻璃的结构。火山岩玻璃在500℃/7.7 GPa静压下致密化(约9%)，可能是由TO_4四面体结构的6元环和5元环为主转变为4元环和3元环主导结构所致。另一方面，在冲击波压缩下，黑铁矿中的微晶被玻璃化，在较高的冲击波压力(25和35 Gpa)下，密度不仅没有增加，反而减少了。d)在日本和法国，所有的项目成员都讨论了这些结果，我们准备了一些科学论文。

Principle results on the structures of feldspar and volcanic glasses for analyzing structures and physical properties of magmas under high temperature and pressure conditions were followed.a) The shock-wave densification of SiO2 glass was analyzed by X-ray diffraction and Raman spectroscopy. SiO2 glass was densified up to 25GPa and the density decreased upper pressure by high residual temperature.b) Feldspar (NaAlSi_3O_8 CaAl_2Si_2O8) glasses were compressed under 500^OC/4GPa and 7.7GPa by cubic press apparatus. The structures of these glasses were analyzed by Raman spectroscopy. From these observations, it was evident that the structure of plagioclase glass has smaller ring structure of TO_4 tetrahedra and the coordination numbers of Al atoms change from 4 to 6 under high temperature and high pressure conditions. Shock experiment for CaAl_2Si_2O_8 glass was also performed to reveal the density increase was smaller than that of SiO2 glass and this density increase was based on the increase of three membered rings of TO_4 tetrahedra. The annealing process of shock-wave denshified CaAl_2Si_2O_8 glass was also investigated by in-situ Raman spectroscopy. These results are very important to understand Al bearing magma.c) The structures of densified volcanic glasses obtained by shock and static compressions were investigated by Xray diffraction and Raman spectroscopy techniques. The densification of volcanic glass (about 9%) by 500^OC/7.7GPa static compression may be due to change from 6 and 5 membered ring of TO_4 tetrahedra dominant structure to 4 and 3 meinbered ring dominant structure. On the other hand, crystallites in the obsidian vitrified by shock-wave compression and the density did not increase but decrease at higher shock pressure(25 and 35GPa).d) These results were discussed in Japan and France by all project members and we prepared some scientific papers.