Coal Accumulation In The Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau is the last mysterious and magical land in China,as well as coal geology.There are many coal mines and coal-bearing strata on the plateau,but the breadth and depth of geological survey of coal resources are very limited.Most of the areas belong to the blank of coal field geological work.In this paper,the basic characteristics of coal accumulation in the Qinghai-Tibet Plateau are studied by using the theories and methods of plate tectonics,continental dynamics and basin analysis,and the following innovative results are obtained.Geological survey results show that there have been eight main coal accumulation periods in the Qinghai-Tibet Plateau since the Early Carboniferous,and 14 sets of coalbearing strata remain in 10 coal-bearing zones in three tectonic areas,which are hosted in six coal-accumulating basins,namely,East Kunlun,Changdu,Tumengela,Gangdise Northern Margin,Lhasa and Gangdise Southern Margin.Among them,four Coal Basins,Changdu,Tumengela,Gangdise Northern Margin and Lhasa,have developed marinecontinental transitional coal-bearing strata,with a large number of coal seams,and some of them are relatively stable.East Kunlun coal basin is mainly continental deposit with few coal seams and unstable coal seams.Coal basins in the southern margin of Gangdise are characterized by the evolution from marine-continental transitional facies to continental facies.There are more coal seams in Eocene transitional facies,some coal seams are relatively stable,and the Miocene-Pliocene transitional facies evolves into continental facies,with fewer coal seams and unstable coal seams.During the Late Paleozoic Carboniferous-Permian,coal accumulation in the QinghaiTibet Plateau was mainly controlled by the evolution of the eastern Tethyan arc basin and paleophytes.Coal-bearing deposits were mainly developed in back-arc basins and back-arc foreland basins along the coastal zone of the continental margin.During the Mesozoic Triassic-Cenozoic,coal accumulation was mainly controlled by palaeogeography and sedimentary environment.Coal-bearing deposits developed in the foreland basin behind the arc of the Changdu block,Tianshuihai-North Qiangtang foreland basin,East Kunlun Intermountain basin,Gangdise interarc basin and strike-slip pull-apart basin.Controlled by plate tectonic movement,the coal accumulation in the Qinghai-Tibet Plateau has a specific temporal and spatial migration law.Early Carboniferous-Late Permian coal accumulation was located at the margin of the Changdu Block,and migrated to the interior of the Changdu Block and the transitional area of the South and North Qiangtang Block in the Late Triassic.Late Jurassic-Early Cretaceous coal accumulation migrated to the northern margin of the Gangdise Block and to the southern margin of the Gangdise Block in the Eocene.According to the characteristics of plate tectonics and lithofacies palaeogeography under its control,seven coal-accumulating basin types are extracted: back-arc basin,back-arc foreland basin,inter-arc basin,fore-arc basin,intracontinental foreland basin,fore-deep basin,and intermountain fault basin.Based on the analysis of the uplift history and denudation rate of the Qinghai-Tibet Plateau,it is believed that nearly half of the uplift height of the Changdu Coal Basin was denuded,resulting in massive outcropping of the Carboniferous,Permian and Triassic strata.The Northern Margin Coal Basin of Gangdise was mainly affected by intrabasinal faults and deep faults along the Nujiang River in the north,resulting in fragmentation of coal-bearing strata.Denudation was relatively weak in Lhasa Coal Basin,but coal-bearing strata were strongly folded and faulted.Coal-bearing strata in East Kunlun Coal Basin were only distributed in the lower wall of thrust structure.Coal-bearing strata in the Basin of Gangdise Northern Margin were distributed in the lower wall of the faults along both sides of the Yarlung Zangbo River.Based on the characteristics of tectonic deformation,the coal resource potential of the main coal-bearing areas in Gangdise Northern Margin,Lhasa and Gangdise Southern Margin is predicted,and the prospects for coal exploration in the Northern Margin Coal Basin of Gangdise are considered to be better.This paper includes 77 illustrations,43 tables and 235 references.