Study On The Formation And Evolution Of The Basin In Neopaleozoic In Area Of Yin'gen-Eji'naqi

The paper topic, study on the formation and evolution of the neopaleozoic basin in area of Yin'gen-Eji'naqi, was chosen to study the tectonic pattern, attributes and basin formation and evolution by analyzing the stratum characteristics, Space-time distribution of magmatic rocks and geochemical characteristics in Carboniferous-Permian of Neopaleozoic.Stratums of Carboniferous-Permian all exposed in the surrounding area,because the re-search area is covered by desert and Gobi. Base on the exposed stratums, the paper will ex-amine the distinction of the east,west,south and north area. The Carboniferous stratums ex-posed in the west area are mainly baishan and lvtiaoshan Formation of the Lower Carbonif-erous and ganquan Formation of the Upper Carboniferous, north, haobiru Formation of the Lower Carboniferous, east, amushan Formation of the Upper Carboniferous, and ganquan Formation of the Upper Carboniferous in the south. Stratums of Permian are shuangbaotang Formation of the Lower Permian,jushitan and jinta Formation of the Middle Permian and fangshankou Formation of the Upper Permian in the west area, maihanhada Formation of the Lower Permian,aqide Formation of the Middle Permian and haersuhai Formation of the Up-per Permian in the north, and jushitan Formation of the Middle Permian and the Upper Per-mian in the south.The Carboniferous Formation are primarily shallow-sea continental and circumscribed seacoast deposits, carbonate platform and braided river delta take second place, while the Permian are primarily shallow-sea continental, open-sea coastal, carbonate platform and fan-delta take second place. The sequence was mainly volcanic explosion in the early stage, subsequently, carbonate and lastly,elastic rocks.Carboniferous and Permian volcanic rocks are mostly calc-alkaline series volcanic rocks, with only small amounts of alkaline series and tholeiiteseries volcanic rocks. Tectonic envi-ronment is stretching in Carboniferous-Permian. Both of the Carboniferous and Permian vol-canic trace elements, the general characteristics of enrichment of LILE and depletion in Nb,Ta and Sr,which was related to contaminated crust and crystallization differentiation of plagio-clase.The rare earth elements show faint negative Eu abnormalities.Intrusiverock was found in research area in Middle-Late Variscan, which was granitoid. The rock type was quartz montzonite, diorite, Granite and granodiorite. The characteristic of granitoid was subaluminous and metaluminous, calc-alkaline series,extensional and extru-sional,S and I type. The general characteristics of the trace elements was depletion in Nb,Ta and Sr and rare earth elements show faint negative Eu abnormalities. The tectonic setting was pre-plate collision,syn-collision and post-collision uplife,which was Complicated.According to the geologic outcrop, physical geography and remote sensing image datas, we divided seven primary faults, five secondary faults and third class faults. By means of geological and geophysical data,the basin in Neopaleozoic has two kinds of different sedi-mentary basements in research area, one is crystalline or sedimentary metamorphic basement in Precambrian system, the other is fold basement in the lower-paleozoic. By the features of stratum growth, lithological association, biological assemblage, sedimentary formation, areal structure and magmaticrock, we divided four first grade and eleven secondary tectonic units in Carboniferous-Permian in the area.The comprehensive research shows that the Carboniferous-Permian are all characterized by rifts and faulted basins, but have different development process. The area of Hongshis-han-Heiyingshan was the stretch to extrusion tectonic environment, the area of Yingen-Ejinaqi was the continental crust risft basin and the area of Bayinnuoergong was pull manufactured continental rift basin.The formation and evolution stage of the basin is divided by the study of strata distribu-tion, contactrelation, sedimentary formation and magmaticrock.1. Stretching stage of basin (Tectionic framework of rift, rifting and limited ocean basin) (D3-C1),2.In full bloom stage of basin (The stage of rift basin fillings and limited ocean basin closed) (C2-P2),3. Shrinking stage of basin (Progradational basin and filling continental basin) (P3),4.Late stage of basin (final stage of P3).