东亚晚前寒武纪大地构造演化

距今约在6亿年至20亿年的阶段为晚前寒武纪时期(表1)。该时期内海、陆地壳的演化表现强烈,留下了较丰富的地质记录。晚前寒武纪大地构造的演化,无疑是在早、中前寒武纪的构造基础上发展的,并且对寒武纪以后的构造演化具有重要的控制作用。所以,研究晚前寒武纪的大地构造演化,对于揭示现今大地构造特征和探讨早、中前寒武纪的大地构造,具有重要意义。

ON THE TECTONIC EVOLUTION OF EAST ASIA IN LATE PRECAMBRIAN

In this article the Late Precambrian is divided into two stages, i.e. Jinning cycle and Salayer cycle, of which the range is from 2000 to 600 my Bp. These two cycles hae exerted a significant influence on the tectonic evolution in eastern Asia.The development of Jinning cycle is distinctly revealed in the southern part of the Yangtze fault block, where eugeosynclinal formation of Sibao Group is well-developed and upper Banxi Group, with its miogeosynclinal ’formation lies upon Sibao Group. The continental crust in eastern Asia was subjected to tension during the Jinning cycle about 1700 my Bp. Therefore a transitional crust or ocean crust was formed in many places such as Yin Shan and Qinling, etc. Strong tensions also occurred in the interior of the Sino-Korean fault block. The compressions at the end of the Jinning cycle consolidated and unified the Yangtze fault block, the Siberia ’fault block and the Sino-Korean fault block, constituding a ancient large continental crust.Salayer cycle(Early Caledonian cycle)developed on the bases of the above mentioned continental crust owing to the tension. Its standard section is in the Salayer-sci Mountains and adjacent areas, where Sinian and lower Cambrian characterized by eugeosynclinal formation. During Salayer cycle, the tension strength, the character of crustal activities and the age of folding in eastern part and southern part of East Asia are quite different from that in the western part and northern part.The fracture play an important controlling role in tectonic evolution. To sum up, the tectonic evolution of Late Precambrian in East Asia was controlled by X-shaped conjugate fracture trending E-W(i.e. fracture along the northern side of the Sino-Korean fault block)and S-N(i.e. fracture oriented at longitude 105°E). In the concrete, the tectonic development was controlled by ’fracture trending NW and trending NE, constituting a fracture network.