Rsearch On The Geological Characteristic And Tectonic Attribute Of The Mesoproterozoic To Early Paleozoic Metamorphic Rock, East Segment Of East Kunlun Orogen

East Kunlun orogenic belt is a composite continental orogen，superimposed by thedifferent stages and types of orogenesis， has long and complicated evolutionaryhistory．Guided by the Plate Tectonic theory and continental dynamics and dominated bysystematic studies on wild-field geological characteristic，petrology，petrologic geochemistryand zircon U-Pb isotope geochronology of the Mesoproterozoic to Early Paleozoicmetamorphic rock in the east segment of East Kunlun orogenic belt，furthermore，on whichthe paper rebuild the tectonic framework and discuss regional tectonic evolution process ofthe area in the Mesoproterozoic to Early Paleozoic．The following cognitions are acquired inthe essay after the wild-field geological mapping and detailed indoor experiments andanalysis to the collected samples of the study area．1、Xiaomiao Rock Formation is mainly composed of felsic rock，superimposed thinknessreach5310.3m，which can be divided into four rock members：quartzite－arkose quartzite unitcombination with plagioclase amphibolite schist and little biotite plagioclase gneiss；Al-richgneiss unit；felsic gneiss unit；quartzite－arkose quartzite unit．The protolith of XiaomiaoRock Formation is mainly terrigenous detrital sediments with basic volcanic rockintermediate layers，and invaded by epigenetic magmation．The petrologic geochemistrycharacter shows that provenance is mainly made up of felsic rock，suggests a warm，moist andmedium chemical weathering circumstance， and basic volcanic rock belongs tointracontinental rift basalt．Taking all factors into consideration，Xiaomiao Rock Formationformed in intracontinental extensional taphrogenic trough or intracontinental riftenvironment．Xiaomiao Rock Formation records at least five period deformation，and thestable mineral assemblages at peak is Alm+Ky+St+Bt+Pl±Ms，indicate that the metamorphicdegree of it can reach the amphibolite facies．2、Langyashan Formation is decke that thrust on the Xiaomiao Rock Formation andNachitai Rock Group，and mainly consists of dolomitic limestone，bioclastic limestone andsillcalite，which indicate a stable neritic basin．3、Nachitai Rock Group is mainly made up of quartz schist，superimposed thinknessmore than3761m，which can be divided into two rock members：biotite quartz schist－garnet two-mica schist unit；quartz schist－sericite quartz schist unit combination with greenschist（metamorphic basic volcanic rock）． The protolith of Nachitai Rock Group isvolcano-sedimentary series combination．The petrologic geochemistry character shows thatprovenance is mainly made up of felsic rock，basic volcanic rock belongs to island arcbasalt．To sum up，Nachitai Rock Group formed in back-arc basin environment．Themetamorphic degree changes from greeschist facies in south to low-amphibolite facies innorth，record at least three period deformation．4、The LA-ICP-MS zircon U-Pb isotopic ages of the metamorphic zircon from XiaomiaoRock Formation and Nachitai Rock Group is1683Ma～1554Ma and （474±7.9） Ma（MSWD=0.59，n=11）respectively，which respectively belong to the Mesoproterozoic andEarly Paleozoic（Ordovician）．5、As response to Columbia Super-continent split，East Kunlun region began to split andformed intracontinental rift in the late Palaeoproterozoic．At the same time，Xiaomiao RockFormation and Langyashan Formation were deposited．The convergent event in the lateMesoproterozoic formed the consolidated Precambrian metamorphic basement which splitedin the late Neoproterozoic in East Kunlun region．There emerges the Proto-Tethys ocean crustin the Early Cambrian，taking the Delistan ophiolite as representation，and subducts northwardin the Middle Cambrian，simultaneously forms a large area of arc magma in Kekesha area andthe back-arc basin represented by the Qingshuiquan-Kekesga-Kekekete ophiolite．It alldeveloped into collision orogeny in the Middle to Late Silurian after subduction orogeny.Helegangnaren granite shows that the post-collision event takes place in the LateSilurian．Maoniushan Formation indicated that East Kunlun turned into another tectonicevolution cycle which closely related to Buqingshan-Anemaqen Paleotethys Ocean．...