Analysis Of The Basement Structure And Tectonic Evolution Of Turpan Hami Basin

Turpan Hami basin is located in Xinjiang,China,and is one of the main petroliferous basins in Northwest China.The basement of the basin has two layers of structure,including the Precambrian crystalline basement and the Paleozoic Carboniferous Permian fold basement.In recent years,the oil and gas exploration in Turpan Hami basin has made significant breakthroughs in Permian Carboniferous.It is imperative to clarify the basement structure and tectonic evolution of the basin.Based on seismic data,gravity and magnetic data,outcrop and drilling data,this paper analyzes the basement structure and sedimentary environment of Palaeozoic and divides the tectonic evolution stages and analyzes the tectonic stress fields at all stages.Based on the analysis of the plotting of the balanced section and the shortening rate of the section,this paper studies the evolution of the basement structure in the basin.The main research results are summarized as the following points:(1)The basement Carboniferous and the lower Permian are widely distributed in the whole basin.The Carboniferous is thicker in the western and northern area and thinner in the eastern and southern area.The thickness difference of the lower Permian is small.The middle and upper Permian are distributed mainly in the central and northern area,and the thickness is relatively thin.(2)The strike of the basement faults are mainly EW and NEE directions.Based on the characteristics of uneven crystalline basement uplift and basement fault distribution,the Palaeozoic fold basement is divided into three first rank tectonic units: the Turpan depression,the Liaodun uplift and the Hami depression.(3)Evolution stages of Paleozoic fold basement in the basin:(1)Carboniferous,back arc rifting stage,(2)Early Permian,Post orogenic extension stage,(3)Middle Permian,Post collision extrusion stage,(4)Late Permian,Intracontinental extrusion stage.(4)During the Carboniferous to early Permian,the sedimentary environment of the basin is marine environment and is accompanied by volcanism.After the Middle Permian,the basin entered the continental environment.(5)Tectonic movements in different periods have different effects on basin basement reconstruction.The formation of the Turpan depression is most intense in the late Himalayan stage and the Yanshan and Indosinian movement have stronger influence in the western area than the east.The formation of the Hami depression is most intense in the Indosinian stage and the Yanshan movement has stronger influence in the western area than the east.The situation is just the opposite in indosinian and the late Hercynian movement.(6)The formation time of Hami depression is earlier than that in Turpan depression.In the Late Palaeozoic,the stress inversion in Hami depression is earlier than that in Turpan depression.The most intense deformation occurred in the Himalaya period in the Turpan depression.The most intense deformation in the Hami depression occurred in the Indosinian period.