Geological Characteristics And Tectonic Significance Of The Middle Late Paleozoic Granites In Quruqtagh, Xinjiang

This thesis studied petrographical,geochronological,geochemical characteristics andpetrogenesis of the middle late Paleozoic granites in Quruqtagh domain through fieldinvestigations and laboratory tests and combined with research findings in adjacent areadiscussed tectonic evolution of the research area during this period,consequently providedfurther constraints for closure time of South Tianshan Ocean,Geotectonic features ofQuruqtagh and tectonic evolution of South Tianshan. Solutions presented in this thesis can besummarized as follows:South Ahongkailide Pluton is mainly composed of monzonitic granite, Zircon LA-ICP-MSdating analyses gave the age of340.6±5.7Ma, implying the magmatic crystallization age ofthe granite.The pluton has high content of SiO2, Al2O3, K2O,but relatively low CaO, P2O5,TiO2and MgO, The values of A/CNK vary from1.14to2.31,C-norm is>1%,suggesting thegranite belongs to high-K calc-alkaline peraluminous S type granite. The granite is relativelyrich in LILEs of Rb，Ba，Th and K, poor in HFSEs of Nb,Ta,Ti in the primitivemantle-normalized trace elements patterns,while the chondrite-normalized REE diagramsshow that the granite is rich in LREE and depleted in HREE with high fractionations of LREEand HREE and moderate negative Eu anomalies((δEu=0.52~0.62),showing the characteristicsof crust derived granites. The formation of South Ahongkailide Granite was closely related tocrustal partial melting caused by crustal thickening The other three plutons located in the eastsection of South Tianshan shows very similar geochemical and petrographicalcharacteristics.Combined with regional research findings,this paper came to the conclutionthat the east section of South Tianshan in the stage of continental collision during the lateperiod of early Carboniferious closed before than the west section.