TECTONIC DEVELOPMENT OF PALEOZOIC FOLDBELTS AT THE NORTH MARGIN OF THE SINO-KOREAN CRATON

Recent study shows that Paleozoic orogeny in Inner Mongolia resulted from collisions. An early event was a collision between an island arc and the North China continent in the Late Silurian, and a subsequent event was a collision between the Sino‐Korean and Siberian platforms before the end of the Devonian. Prior to the collisions, an old Asian ocean existed. Its opening in Inner Mongolia is interpreted from the Middle Proterozoic Zartai rift zone. Late Proterozoic‐Early Paleozoic spreading and subduction are represented by a fossil trench‐island arc‐basin system, which constitutes the Xar Moron accreted fold belt along the north margin of the North China platform. Latest Silurian molasse unconformably overlies these belts, constraining the time of collision between the island arc and the North China continent. The old Asian ocean basin persisted but was finally closed by the collision between the Sino‐Korean and Siberian continental platforms. Latest Devonian‐Early Carboniferous molasse and epicontinental carbonate deposits unconformably overlie an imbricated oceanic rock suite bordering the suture zone, indicating that the collision occurred before the end of the Devonian. This collision produced only a weak orogeny with thin, local molasse and moderate deformation. The Silinhot belt marks this collision and represents the suture zone between the two great platforms. During the Carboniferous and Permian, Inner Mongolia and adjacent regions were affected by widespread development of continental rift structures with intense magmatic activity. Copyright 1990 by the American Geophysical Union.