Gonghe Aulacogen And Conjugate And Transfer Between The West Qinling And East Kunlun Orogens

As major parts of the central orogenic system, the Qinling and Kunlun orogens constitute a giant orogenic belt that stretches from east to west in central China. The orogenic belt has played an important role in the formation of China's continental tectonic framework and the differentiation of today's China environment on both sides of the belt.However, due to structure discontinuity in the Gonghe area in the northeast Qinghai-Tibetan plateau, that is the so-called "Gonghe Gap" between the west Qinling and east Kunlun orogens, some disagreements on the tectonic relationship of the two orogens have long existed among geologists. Some researchers even doubt if the two belong to the same orogenic belt. Thus, the origin of the Gonghe Gap has become a key issue on China's continental tectonics.In pursuit of the origin of the Gonghe Gap, the present study has selected an area between the border of Gansu and Qinghai provinces in east and the Tianjun-Wulan-Dulan-Maduo counties in Qinghai province in west, and the A'nyemaqen mountain and the Qinghaihunanshan mountain in south and north respectively as a study focus. Based on previous investigation and researches, the study has carried out some detailed field work in key portions in the study area, aiming at exploring conjugate and transfer relations for the west Qinling and east Kunlun orogens, and their dynamic characteristics according to their composition, structures and evolution processes in the conjoining area between the west Qinling and east Kunlun orogens.Having summarized and analyzed present major issues of the west Qinling-east Kunlun and the neighboring east Qinling, Qilian, Kunlun and Bayankala orogenic belts, the study briefly discusses essential features of the above orogenic belts closely related to the conjugate and transfer relationship of the west Qinling-east Kunlun orogens and put stress on all deformation structures occurred during extensional period, subduction-collisonal orogeny, collisional orogeny and post orogeny. Also, this study comprehensively analyzes geophysical determination results from depth and geology and geochemistry as well as tectonic settings of ophiolite, basic dyke swarm, collision-type granitoids formed in the conjoining area. Furthermore, petrofacies-paleogeography of the conjoining area is discussed in light of stratigraphy and paleontology. Finally, a 4-D dynamic evolution model of the west Qinling-east Kunlun conjugate and transfer (Gonghe aulacogen) has been established on the basis of the above work.1. The ophilite melange zone in southern east Kunlun, A'nyemaqen-Wenxian-Mianlue ophilite melange zone and Kuhai-Shaishitang ophilite melange zone spatially and temporally form the typical Qinling-Kunlun triple conjunction tectonics. Characterized by the ophiolite melange with major component of alklibasalts which represent apaleo-mantle and hot spot product, the south of the Majixueshan probably is the site of the triple junction. The Qinling-Kunlun triple conjunction tectonics is considered to be the core structure for connecting Qinling, Qilian, Kunlun and Bayankala orogenic belts together in terms of time and space, while the Gonghe aulacogen in the triple conjunction tectonics probably represents the main tectonic form that separates the west Qinling from the Qaidam massif but does not affect their unification (both belong to the Qaidam-Qinling micro-plate) and through that the west Qinling and east Kunlun were conjugated and transferred.2. Structural deformation in the conjunction area can be recognized in four main stages: extension, subduction-collision, collisional orogeny, reworking stage of post orogeny. Deformation in the different stages possesses distinctive structure patterns that reflect corresponding tectonic settings.3. By tectono-petrofacies and paleographical comparison of the west Qinling orogen and the east Kunlun orogen with the conjunction area, it can be inferred that the area has experienced passive rifting, active rifting and foreland basin evolution processes of different basin dynam...