【摘要】 贺兰山北段孔兹岩系中最有代表性的两类岩石 :变粒岩及富铝片麻岩天然块状样品的脱水熔融实验研究表明 ,在不同的温度压力条件 ,两类岩石产生明显不同的变质反应 ,其中变粒岩类在所有的实验条件下均产生 Bt+Pl+Qz→ Hy+Kf+M(熔体 )的反应 ,而富铝片麻岩在不同压力下出现不同的变质反应 :0 .4 GPa条件下发生 :Bt+Pl+Qz→ Hy+Kf+M;0 .6 GPa条件下发生 :Bt+Qz→ Sil+Kf+M;0 .8GPa条件下发生 :Bt→ Cud+Kf+M。本文认为制约变质反应的主要因素是岩石的结构构造 ,因此在讨论高级变质作用时更要强调压力的重要性更多还原

【Abstract】 Based on the solid sample experiments of Al rich gneiss (H029) and biotite granulite (H013), the structure of rock can constrain the proceeding of metamorphic reaction. This paper discusses the mechanism and emphasizes the significance of pressure in metamorphism. The results of dehydration meting experiments indicate that in biotite granulite can be produced metamorphic reaction: Bt+Pl+Qz→Hy+Kf+M at all experimental conditions of temperature and pressure, but the case is different for Al rich gneiss. The reaction: Bt+Pl+Qz→Hy+Kf+M can appear only at 0.4 GPa (Table 2 and Fig. 2). Metamorphic reactions are different at different pressures. Reaction Bt+Qz→Kf+Sil+M can occur at 0.6GPa, but at 0.8 GPa reaction Bt→Cud+Kf+M can be observed. Differences in structure of rock are the main reason for different metamorphic reactions because biotite granulite is provided with massive structure and granular texture, thus its mineral and chemical compositions are homogeneous in the whole rock. So the reaction cannot be influenced by structure and texture of the rock. But Al gneiss exhibits stripped or gneissic structure, thus its chemical and mineral compositions are heterogeneous. Metamorphic reaction is constrained not only by pressure and temperature, but also by the kinetical style of an element. At lower pressure, the diffusion rate and convection rate are higher than those at high pressure, so more reactants would be involved in reaction. As a result, Hy+Kf is formed, but at higher pressure (0.8 GPa), only little mineral would be involved in metamorphic reaction to produce Cud+Kf. The experimental results show that the reactants and products are different in the rock whose mineral composition is unhomogeneous at different pressures. The role of pressure should be emphasized in the study of metamorphism.更多还原