东北、华北几个典型太古宙地体的地球化学特征——中朝准地台早期地壳演化的特殊性

东北和华北太古宙地体和国外同类组合相比有特殊性,如麻粒岩多为非亏损型,仅有少量亏损型,未见熔融残留型等等。这些都表明中国前寒武纪古陆稳定与活化反复交替进行的准地台型发展历史。很可能早期地壳以垂直运动为主,下陷与抬升震荡频繁,振幅不大,因此深部下地壳岩石(残留型或亏损型麻粒岩以及堆晶相层状岩体)较少出露,上部表壳岩和BIF得以较多保存,绿岩盆地发育不好,稳定性差,变质较高,形成了以“钾质”为主,无红(风化壳型铁矿)少绿(绿岩带)、透镜状BIF广泛分布于中一高级片麻岩中的地质景观。

The Characteristics of Archaean Crust Evolution in Sino-Korean Peneplatform:Geochemical Evidences

There are obvious geochemical differences in Archaean terrains between China and other areas in the world.They are as follows: 1. Most granulites facies in north China have normal chemical contents, only a. few granulites deplete chemistry and no granulite is of residue phase of partial melting. 2. The amounts of cumulate part of layered ultramafic-mafic bodies are relatively fewer, any layered anothosite body has not been reported so far. 3. Greenstone belts including komatiite are not abundant. 4. The dominant rocks are granitic(pinkish) other than grey gneisses that suffered metamorphism and removing many times. 5. Much more pods of supracrustal rocks and BIF occure in gneisses. 6. The cratonization of Sino-Korean Peneplatform ended about 1.7 Ga.ago,it is much later than those of north Americs, south Africa and west Australia Shields. The possible tectonic model of Archaean crust evolution in Sino-Korean Peneplatform is proposed, which isbased on dominantly vertical movement with frequent vibrations, and the amplitudes were not big.