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问题回顾长期来,变质岩主要用岩石学观点来从事研究,甚至到本世纪初,在有些文献和许多地质图中,前寒武岩层并非按其年代划分,而只是根据重结晶程度标■属“变质片岩”或“结晶片岩”(片麻岩)。然而已意识到将这些岩层划归地层系统是必要的。局部地区的地层划分可应用于某些地区的前寒武岩层中。英国地质学家Sedgwick于1836年建立了寒武系,又在1838年建议所有叟老地层
Review of the problem For a long time, the metamorphic rocks were mainly studied from the petrologic point of view. Even in the early part of this century, in some literatures and many geological maps, the Precambrian layers were not classified according to their ages but only on the basis of degree of recrystallization “Metamorphic schist” or “crystalline schist” (gneiss). However, it has been recognized that it is necessary to assign these formations to the formation system. Stratigraphy in some areas can be applied to Precambrian formations in some areas. British geologist Sedgwick established the Cambrian in 1836, and in 1838 proposed all the old formations