Chronology,Geochemical Characteristics And Its Tectonic Setting Of Volcanic Rocks From Manketouebo Formation In Suolun Area,Central Great Xing'an Range

This thesis is based on the Manketouebo Formation volcanic rocks of Suolun area in the central Great Xing'an Range as the research object.It has carried on the petrology,rock geochemistry,zircon U-Pb,in situ Lu-Hf isotopic chronology and research,in combination with area on the basis of predecessors'work,in order to discusses its formation age,rock formation and tectonic setting.1.Manketouebo Formation volcanic rocks are given priority to with rhyolite,rhyolitic?including detritus,crystal pyroclast,beccia?tuff lava,ignimbrite and tuff,meanwhile with a small amount of pyroclastic sedimentary rock and dacite.2.The results of LA-ICP-MS ziron U-Pb dating from Manketouebo Formation volcanic rocks are 138±1.5Ma,139.9±2.5Ma and 139.8±1.4Ma,ircon U-Pb dating results show that they formed at early cretaceous.3.Geochemical data of Manketouebo Formation volcanic rocks shows its high silicon,rich alkali,weakly peraluminous-peraluminous?A/CNK=0.99¹.34?,the characteristics of the high degree of differentiation,belongs to high potassium calc-alkaline series,relative enrichment of light rare earth and parts of LILE?Rb,Th,U?,loss of HFSE?Nb,Ta,Ti?,has the characteristics of high differentiation type I volcanic rocks.4.Zircon Lu-Hf isotopic composition indicate that Manketouebo Formation volcanic rocks have positive values of?_Hf?t??+4.06⁺8.24?and?+4.25⁺9.27?,and young Hf two-stage model ages 936⁹36 Ma and 664⁶04 Ma,that its probably originated in the Neoproterozoic-Phanerozoic from depleted mantle hyperplasia young partial melting of crust material.5.Manketouebo Formation volcanic rocks formed in the post-tectonic extension environment.The stretch of tectonic setting may be closely related to the orogenic belt stretch after the Mongol-Okhotsk Ocean closure.