中国末前寒武纪古地理格局

根据古地磁学与地质学方面的资料再造了末前寒武纪800-600Ma期间中国大陆区内4个板块的原始位置及相互关系。

THE TERMINAL PRECAMBRIAN PALAEOGEOGRAPHIC FRAMEWORK IN CHINA

The time interval discussed in this paper ranges from 800 to 600 Ma B. P.The mainland of China consists of five major massifs. They are: the Sino-Korean, Yangtze, Tarim, Cathaysian and Tibet-Indian plates. The relationships of the above plates determined the palaeogeographic framework with a time range of 800-600 Ma. As information is limited, it is impossible to discuss all the five plates. This paper centres on the relationships of the Sino-Korean, Yangtze, Tarim and Cathaysian plates.Palaeogeographic maps (Figs. 2-3) were compiled on the basis of the pa’aeomagnetic and other data, which show the following characteristics of the Terminal Prccambnan palaeocreog-raphic framework in China:1) The Sino-Korean plate was far away from the Yangtze plate, both being separated by oceanic crust. The former was located between lat. 80°-40°N during the Yangtzeian and between 50°-30°/N during the Sinian.2) According to the data available, to the east of the Yangtze plate there exists a gigantic Precambrian massif which occupies the greater parts of Fujian and Zhejiang provinces an the Southeast China continental shelf. The authors suppose that this massif would probably be connected with the basement of the platform of the Indosinian Peninsula towards the west, and with southwest Japan towards the northeastern. It is a huge plate with a vast area, known as the Cathaysian plate. Its northwestern part was connected with the Yangtze plate during the Terminal Precambrian. However, there was a bathyal trough, known as the South China Sea Trough, between the Yangtze and Cathaysian plates.3) The Tarim plate might be connected with the Yangtze plate and Cathaysian plate during the Yangtzeian. They were all located in the same low-latitude (30°-10°N) zone and the Yangtzeian glaciation was restricted between lat. 30°-17°N. On the other hand, being far away from the Yangtze plate, the Sino-Korean plate was lacking in glaciation.4) During the Sinian, the Yangtze-Cathaysian plate was separated from the Tarim plate and drifted to the locus between lat. 15°-0°N, while the Tarim plate essentially stayed where it was. The Sino-Korean, Tarim and Yangtze-Cathaysian plates were three independent blocks separated from one another by oceans. Although the Tarim plate was separated from the Yangtze-Cathaysian plate, it is closely related to the latter, which has been supported by both sedimentary and biogeographical evidence.5) During the period from 800-600 M1 B.P., the Sino-Korean plate belonged to the Northern China tectonic domain, and the Tarim, Yangtze, Cathaysian plates and South China Sea Trough to the Southern China tectonic domain.6) It is impossible to find the Terminal Precambrian section of the transitional or intermediate type between the Northern China and Southern China types. The correlation between the Terminal Precambrian sections of the northern China tectonic domain and the southern China tectonic domain can only be done with the aid of geochronostratigraphy and biostrati-graphy.