关于区域变质作用,过去一般认为是一种等化学作用,即除一些易挥发组分(如H_2OCO_2等)可能有所变化外,其主要造岩元素在区域变质作用过程中并不发生什么迁移。正因为基于这一传统观念,因而曾使许多人设想利用区域变质岩的岩石化学成分来恢复原岩的性质,并设制了各种投影图或判别式。应该肯定,任何一种投影图或判别式都是人们根据大量 For regional metamorphism, the past is generally considered to be an iso-chemical effect, that is, except for some volatile components (such as H 2 OCO 2, etc.) may have changed, the main rock-forming elements in the metamorphism in the region does not occur any migration. Precisely because of this traditional concept, many people have envisaged using the petrochemical components of the regional metamorphic rocks to restore the original rock’s properties and formulating various projection diagrams or discriminant formulas. It should be affirmed that any projection or discriminant is based on a large number of people