Intraplate Tectonics Of Bogda Mountain In Xingjiang And Its Adjacent Plates

Bogda mountain and its adjacent areas are in the hinterland of the Asia continent. Its current regional geology is characterized by mosaic relation between landmass and orogenic zones and coexistence of basins and mountainous chains,which formed a complicated structural configuration,the huge metallogenic province in central Asia with abundant energy and mineral resources.It is not only one of the best natural laboratories for research of continental dynamics and discovery of geoscience,but also it is one of the important metallogenic provinces in China.Studies of the Mesoand Cenozoic intracontinental orogeny and their dynamics in the Bogda orogenic zone and its adjacent areas present practical significances in scientific researches and economy.With the theory of plate tectonics and new knowledge of intracontinental geology and dynamics and on the basis of previous researches and regional geological information,including geology,seismic and drilling data obtained from the Bogda orogenic zone,Tulufan-Hami basin and Santanghu basin,a comprehensive analysis of the structures in those basins and the orogenic zone has been done and a systematic analysis of the characteristics of intracontinental structures in the Bagda tectonic belt and its adjacent regions has been carried out.Following result are obtained from this study:1.Spacial distribution of ophiolite and ophiolite complex,magmatic activities, metamorphism and tectonic deformation revealed that the Altai,Tianshan Mountains and their adjacent regions experienced subduction of ocean-basin,orogenetic collission between continents,resulting in close of the regional oceanic basin in the north Xinjiang and forming the folded basement of the Bogda tectonic zone,adjacent Zhungeer basin,Tulufan-Hami basin and Santanghu basin,ending the process of plate tectonics of transformation between ocean and continent in the Permian period and entering a new period of intracontinental tectonics.2.Based on field geological work,analysis of seismic sections and drilling log, sedimentary characteristics and magmatic activities,the basic tectonic pattern of coexistence of basin and mountains occurring in Bogda area and its adjacent regions is confirmed.The Bogda mountain is present as an anticlinorium structure with thrust nappe,forming a composition of a fan-shaped fold and thrust structures.Basins at both sides of Bogda mountain are down-warped basins controlled by ramp and nappe structures.Those boundary structures made configuration of the characteristics of structures and sedimentation in the basins and the current structural patterns were formed in the Cenozoic era.3.The characteristics of Bodda mountain and its adjacent regions were the final result of the Himalayan movement,including multiphase tectonics in Hercynian, Indosinian and Yanshanian periods in the intracontinental plate,thus making the configuration of the basic features of structures.4.Isotopic dating and lithogeochemical analysis revealed that the intrusive rocks and volcanic rocks in Bogda mountain,Tulufan-Hami basin and Santanghu basin were formed in Permian period,in which gabbro,diabase and basic volcanic rocks are similar to the basalt in intracontinental extensional belt and primary rift.The Early Permian sedimentary configuration in Bogda mountain and its adjacent basins are characterized by normal grading from coarse to fine,being a typical extensional molasse.The regional geological information of Zhungeer Basin and the features of volcanic-sedimentation and magmatic activities indicated that the Bogda mountain and its adjacent basins in the Early Permian period were an extensional environment after orogeny.5.Bogda mountain has experienced multiphase stages uplift including Hercynian, Yindosinian,Yanshanian and Himalayan periods.Comprehensive analysis of the statistics of high debris content,heavy minerals and paleocurrent trend in the basins at both sides of Bogda mountain indicate that the initial time of uplifting again of Bogda mountain was in the late period of Middle Jurassic Xishanyao time the strong upwarding of Bogda mountain occurred in the Cenozoic era and the golden age of the mountain-building was in the early Miocene period.