摘要
国际前寒武纪地层分会在对太古宙划分的酝酿方案中，提出以３．６Ｇａ，３．２Ｃａ和２．８Ｇａ为时间界线，将太古宙分为Ｅｏａｒｃｈｅａｎ，Ｐａｌａｅｏａｒｃｈｅａｎ，Ｍｅｓｏａｒｃｈｅａｎ和Ｎｅｏａｒｃｈｅａｎ等４个代。这是可以接受的划分方案。但作者根据中国目前测得的太古宙年龄资料，特别是反映热－构造事件的深成花岗岩的同位素年龄数据，建议以３．８Ｇａ，３．３Ｇａ和２．９Ｇａ为时间界线，将太古宙４分为冥（始）太古代、古太古代、中太古代和新太古代。新太古代可再分为上、下两个单元，时间界线约在２．６５～２．７Ｇａ之间。太古宙的顶部时间界线仍定为２．５Ｇａ。
The item of Archean means that the geological history is a very long period before 2.5 Ga.It is characterized by, the intensive crust-mantle differentiation, widespread remobilized.and reworked crusts, and complex metamorphism and deformation. Because it had undergonestrong tectonic movements, the geqlgical records of the earliest history of the earth werenearly all destroyed, and only in a few areas are poorly preserved. Same as in the world,Archean rocks in China are also dominantly high-grade granulite-gneiss assemblages aridmiddle-low-grade granite-greenstone assemblage. We generally agree to the scheme of foursubdivision of Archean which was recommended by the internationa Subcommittee of Precambrian Stratigraphy in its ninth session. But according to the geology situation of China,we prefer to select the ages of 3.8 Ga, 3.3 Ga and 2. 9 Ga as the boundary times forEras. The geological period before 3. 8 Ga is named the Eoarchean Era. It is the earliest eraand alsq the least geolgical records in the earth history.The Paleoarchean is the era between 3.8 Ga and 3. 3 Ga.The Paleoarchean crustal remnants in China have been only discoved intab areas so far.One is in the Eastern Hebei and the other is in Anshan of LiaoningProvince.In addition to the above mentioned two areas,the Mesoarchean rock records (between 3. 3 Ga and 2.9 Ga) occurred as crustal remnants in varying scale have been found inthe Long gang Cbmplex-Group in Liaoniang-Jinn provicea, in the Sanggan Complex withinthe juncture of Hebei-Inner Monglia-Shanxi provinces,and in the Jiaodong Complex-Group ofShandong Provice.The Neoarchean is an era in which the Archean rock records arewidespread,and the granite-greenstone belts are also well developed in China.According tothe relatively abundant geolgical data and isotopic ages, the Neoarchean can be reasonablysubdivided into two stages;and the age of boundary is suggested at 2. 65-2. 7 Ga. About thetop boundary of Archean,we use the age of 2. 5 Ga, which was determined by the international Committee of Stratigraphy.
