大陆地壳主要构造的演化

地壳变动不仅具有短时间的旋迴性,而且具有长时期的旋迴性。同位素年龄数据和各大陆地质年表说明,在地球演化历史中具有约8-10亿年间隔的最巨大的旋迴性,它们的年龄峰值为～3.6、～2.6、～1.9、～1.1及0.2b.y.五个巨旋迴。 结合中国及世界各大陆构造带（变质带及岩浆作用）产出位置及年龄可以看出,第二巨旋迴（～2.6b.y.）时期大致是NNE-NNW向为主;第三巨旋迴时期（～1.9b.y.）主要是NEE-NWW向;第四巨旋迴时期（～1.1b.y.）又重新转为NNE-NNW向;但在第五巨旋迴（0.2b.y.）则比较复杂,NEE-NWW向及NNE-NNW向分别出现在欧亚板块及其它地区。全球主要构造演化模式可能意味着,大陆地壳不止一次遭到碎裂作用,使古老基底被分割成许多断块,这种碎裂作用或许正是按上述一定构造方向发生和发展着的。

ON THE PRINCIPAL TECTONIC EVOLUTION OF CONTINENTAL CRUST

It has been suggested that the tectonic movements in the Earth's crust involve not only the short-term cycles but also the long-term ones. Judged from the available data on isotopic dating and geological time scales of various continents there may have existed five chelogenie cycles separated by an interval of 0.8-1.0 b.y. and their peak age values turn out to be 3.6, 2.6, 1.9, 1.1 and 0.2 b.y. throughout the history of the earth's evolution.Based on the distribution of the tectonic belts （metamorphic belts and magmatism） in various continents as well as their geological ages, it is shown that the chelogenie cycle Ⅱ （ 2.6 b.y.） is characterized chiefly by tectonic belts with NNE-NNW trend, the chelogenie cycle Ⅲ （ 1.9 b.y.） by the NWW-NEE trend, while in the chelogenie cycle IV the belts had the same trend as that of chelogenie cycle II. As to the chelo-genie cycle V （ 0.2 b.y.） its tectonic belts became relatively complicated, trending both NEE-NWW and NNW-NNE and extending over the Eurasian plate and other areas respectively. The model of principal global tectonic evolution proposed here im-plies that the continental crust has undergone more than once tectonic event which developed probably along the tectonic trends mentioned above leading to the formation of fault blocks in the old basement.