Geological And Geochemical Characteristics Of Carboniferous Volcanic Rocks In Bailing Mountain Of Eastern Tianshan And Their Implications For Tectonic Evolution

In this paper,stratigraphy,chronology,petrochemistry and paleontology of the achishan formation,the Yamansu formation,and the Tugutubrac formation of the eastern Tian Shan mountains were studied.Zircon SHRIMP dating of the upper samples of the Aqishan formation was performed,and the age was 342.6 ± 2.5 Ma,indicating early carboniferous,and the geochemical data correspond to the island arc environment.By jamin enrichment Yu Yamansu individuals,groups,the lithologic section of fossils,according to all kinds of brachiopods shells and coral survival environment characteristics,it is concluded that early early carboniferous epoch Yamansu group overall is still in the shallow sea sedimentary facies,normal salinity,water depth < 200 m,the water temperature in normal and volatility is weak,there is no big tectonic movement.Until the late early carboniferous,the East Tian Shan tectonic movement was active.The lithology of the western part of the Yamansu formation is a series of calc-alkaline coarse andesite,while the central part is a series of basaltic andesite of middle potassium-calc-alkaline series.By calculating the crust thickness,subduction depth,closing rate combined with rogge tager tectonic belt Yamansu group in Eastern,central and western volcanic eruption time limit of 348 335.9 Ma and 334 Ma,Ma,according to the overall formed in the early carboniferous,and from east to west,the characteristics of the volcanic rocks in the younger age,suggesting that a more mature western central island arc environment.The geochemical characteristics of tugutubulake formation show that the geodynamic background is extensional environment,the whole is the end-post-subduction collision stage,and the whole shows the characteristics of volcanic rocks in the collision arc region.Late synthetically analysis of early carboniferous,Tian Shan mountain,the ridge to start activities,promoting oceanic crust subduction,the subducting a forward dive,dive Angle,from east to west subduction depth and subduction rate difference,cause jueluotage area more strongly than the subduction formation in middle,crustal thickening scale is bigger,and to induce "scissors" subduction mechanism of volcanism,then the ocean basin closed continuously,and finally form the western lithologic differences in Marine volcanic sedimentary formation,when this process continues until the late carboniferous basic end,sleep luo tager structural belt in intraplate evolution stages.