PLATE-TECTONIC FRAMEWORK AND DISTRIBUTION OF MINERAL RESOURCES IN THE EASTERN QINLING MOUNTAINS,HENAN

The Eastern Qinling structural belt in Henan represents a structural suture zone between the North China landmass and the Yangtze landmass. The northern boundary is the Heigou-Luanchuan-Weimosi-Queshan-Gushi deep fracture zone and the southern boundary is the Xiangfan-Guangji deep fracture zone at the northern margin of the Yangtze landmass. There is an old Huiyang median massif within the Eastern Qinling structural belt. The nothern Qinling geosynclinal fold belt north of the massif is the product of development and evolution of the structure between the ancient Eastern Qinling oceanic plate and the ancient North China landmass. The Southern Qinling geosynclinal fold zone south of the landmass is the product of development and evolution of the oceanic basin at the northern margin of the ancient Yangtze landmass. The massif itself was once an island arc near the margin of the Yangtze landmass in Proterozoic time. The southern and northern landmasses eventually collided in late Hercynian time, with the result that the ancient Qinling sea that lay in between them disappeared. The Shangnan-Xixia-Tongbai-Xinyang-Shangcheng line is just the suture line resulting from the collision. According to the geological characteristics within the structural belt such as deep fracture zones, ophiolites, ancient subducted complexes, mélanges, low temperature/high pressure metamorphic zones, island arc complexes and continental-margin volcanic rock series, the authors divide the Eastern Qinling into （1） the southern North China landmass margin zone, comprising the continental-margin volcanic arc and the volcanic back arc basin; （2） the Northern Qinling continental accretion zone, consisting of the Proterozoic accretion zone,the late middle Proterozoic rift zone, the Caledonian accretion zone and the Variscan accretion zone; （3） the Huiyang median massif and （4） the northern Yangtze landmass margin accretion zone. Its process of evolution is as follows. In the early part of the middle Proterozoic, the Eastern Qinling oceanic plate was subducted northwards towards the North China landmass and an Andes-type continental-margin volcanic arc was formed at the southern margin of the North China landmass. In the middle part of the middle Proterozoic, a back-arc basin was formed behind the volcanic arc that had not yet been peneplained. In the late part of the middle Proterozoic, extension occurred in the front of the continental margin and thus a rift zone was formed. In Yangtzian time at the end of the Proterozoic, the Eastern Qinling oceanic plate was once again subducted towards the North China landmass, causing fold inversion of the middle and late Proterozoic sediments and their accretion to the southern margin of the North China landmass. The subduction also caused fold inversion in the rift zone, forming an orogenic zone. Meanwhile, the Yangtze plate had originated to the south of the Qinling old sea. In Caledonian time, the "Qinling axis" island-arc system was formed in the Eastern Qinling sea near the southern margin of the North China landmass. Ophiolites were deposited in a marginal sea between this island-arc system and the North China landmass. At the end of Caledonian time, the Eastern Qinling oceanic plate was once more subducted towards the North China landmass, causing successive fold inversion of the sediments of the marginal sea and the island-arc system and their merging and accretion to the southern margin of the North China. Then, between the North China landmass and the Yangtze landmass, only a narrow and long sea area was left, receiving the late Paleozoic sediments. During late Variscan time, the North China landmass and the Yangtze landmass collided and were sutured, forming the Chinese continent. Then the area entered a new epoch of geological development. In the Eastern Qinling structural belt, different types of mineral resources occur in different structural positions. The division of the plate into tectonic units is conducive to mineral prospecting.