Major Geological Features of Yinshan Mountains: an Orogenic Region from Craton to Orogenic Belts

　The Yinshan mountains is located in the interior of the eastern Asian continent and is characteristic by the exposure of a large area of the early Precambrian, including the Neo-Archean and Paleo-Proterozoic metamorphosed complexes and late Paleozoic and Triassic plutons, and by multi-age thrusting tectonics with south- and north-verging movement. In the early publications, the mountains was considered as part of so-called Sino-Korean paraplatform, which is considered as same-meaning term with North China craton, imply its difference from the typical platform on the Earth. Since 1990’s, Mesozoic magmatism and structural deformation has been related to within-plate or intracontinental orogeny, and late Paleozoic magmatic rocks to  the Andes-type of orogeny in the southern continental margin of the Paleo-Asian ocean between the North China in the south and Siberian platform in the north. However, the mountains have been still considered as part of North China Craton almost in all of publications, implying no change of its tectonic affinity. Whether the mountain is part of the craton or not, how it was changed from the Craton into the orogenic belt if it is not, is not only a regional or local tectonic issue, but also related to ones of the continental dynamics, and deals with the scientific access of resource potentials. In this paper, the mountains is divided into three tectonic units based on available data both of magmatic rocks and structural deformation. The north unit is part of the island–arc type of an accreted orogenic belt developed in the area north to the North China craton during the early Paleozoic, the central one is an activated orogenic belt on the basis of and by the activation of the northern marginal part of the Craton from the Devonian to Triassic, and the south is an activated intracontinental orogenic one in the interior of the Craton in the period from the Jurassic to early Cretaceous. It is further clearly stated that the so-called North China craton in the mountains is composed only by the southern two units and that the central unit was changed from the craton into the orogenic belt by Devonian to Triassic magmatism and Permian to Triassic structural deformation, and that the south by two extension-compression tectonic cycles taken place in the period of the Jurassic and the Early Cretaceous, respectively. Then it is obtained the following conclusion that the mountains has lost its tectonic affinity of the craton since the late of the early Cretaceous and become part of the North Asian orogenic regions. In the same time, it is the first time to publish some new data on structural deformation from those three units and put forward to some new viewpoints on the mountains which include the formation of the present geomorphological features in the late of the Cenozoic, occurrence of a large scale of crustal shortening in the latest of the Paleozoic, the late of the Jurassic and the late of the early Cretaceous, respectively, tectonic division of four sub-belts of the central unit, three stages of structural deformation of Baiyunebo group sedimentary sequences from tight folding in the early one, and then the right-side strike-slip in the second and to northward thrusting in the third, occurrence of the intensely north-verging thrusting of the south unit in the late of the early Cretaceous. The name system of tectonic division used to the active region of the crust is primarily discussed. Lastly, some suggestions on the tectonic issue which remain to further study and investigate in the mountains, are briefly stated.