Paleoplate tectonics between Cathaysia and Angaraland in inner Mongolia of China

Abstract

On the basis of recent investigations in southern Inner Mongolia the authors consider that there are two Proterozoic rifts of E–W trend in the northern margin of the North China Platform. The Zhaertay Group and Baiyun'ebo Group of closed lagoon facies or neritic facies were deposited respectively in the two rifts. The lead isotopic dating of carbonaceous limestone from the middle sequence of Baiyun'ebo Group yields an age of 1500 Ma. Along the rifts a series of alkaline volcanics and intrusions is scattered in the Yinshan Mountains and Yanshan Mountains. To the north of the rifts, four ophiolite belts and at least five accreted terranes of various ages have been recognized in the Paleozoic orogenic zone. The presence of the ophiolite suites and these accreted suspect terranes in Inner Mongolia indicates that probably there was an open ocean between Siberia and North China in Paleozoic times, when repeated subduction of the oceanic crust had occurred along both continental margins. The suture line between Cathaysia and Angaraland extends from Linxi to Solon Obo. In the late Permian, epicontinental mountain systems of the two converging continents collided with each other. From the analysis of the tectonic evolution of Inner Mongolia and adjacent areas we conclude that the evolution of the southern margin of the Siberian Platform is approximately the same as the history of activity of the trench‐arc‐basin system in the eastern Asian epicontinental areas during Mesozoic and Cenozoic times but the northern margin of the North China Platform is similar in evolution to the Cordilleran system in western North America.