Abstract: Seven types of typical rock wave velocity are classified according to the relationship of mineral composition,origin of the crystalline rocks with absolute values of the wave velocities at high pressures and room temperatures, and the relationship of the wave velocities with phase assembly transformation at high pressures and high temperatures. And at a certain structural envirement, in the light of the relation of variational wave velocity of the rocks with crustal depth, we suggest the concept of rock grade which reflects acidity or basicity of rocks. Its meaning is that with the values from seismic refraction sounding at a certain depth we can have rock grades of the comprehensive rocks at the same depth. On the basis of above principles, we study the composition of the crust of North China, the generation and exsisting conditions in the crust for the amphibolite, the phase of the quartzite and generating cause of the low velocity layers in the crust.

Key words: North China, Crystalline rock, Wave velocity, Phase equilibrium, Rock grade

摘要： 根据结晶岩的矿物成分、成因类型与高压室温下波速绝对值的关系,以及高温高压下岩石波速与物相变化的关系,把岩石分为7种波速类型。在一定的构造条件下,根据岩石波速随地壳深度的变化关系,提出了岩石级数的定量概念,它反映了岩石的酸性(或基性)程度,并可根据地震测深值获得相应深度下综合岩石的平均级数。在此基础上,对华北地壳的组成,角闪岩在壳内的生成和存在条件,地壳内石英岩的相和壳内低速层的成因等问题进行了讨论。

关键词: 华北, 结晶岩, 相平衡, 波速, 岩石级数