Geologic Feature And Tectonic Evolution Of Ertix Tectonic Belt Of Xibodu In Altay Area, Xinjiang

The Ertix tectonic belt, an important part of the Central Asian Orogenic Blet, is the boundary of the Junggar plate and Siberia plate. The special regional tectonic position, makes it became an important tectonic boundary in the northern Xinjiang. The composition of the material, time division, tectonic attributes and other issues of the tectonic belt have been controversial. Combined with previous data, the paper takes the Ertix tectonic belt of Xibodu in Altay region as the research object. The detailed researches of the Keketale pluton and Sinian Fuyun terrain contain petrology, petrography, geochemistry and LA-ICP-MS zircon U-Pb chronology study, and discussed the rock combination, petrogensis, forming environment, time division, the degree of metamorphism and tectonic deformation.The Ertix tectonic belt in Xibodu is mainly composed with the Keketale pluton and Sinian Fuyun terrain. The Keketale rock is composed of gneissic diorite, gneissic granodiorite, gneissic adamellite and gneissic syenite. The LA-ICP-MS zircon U-Pb age gained from the gneissic diorite is 528 ± 16 Ma, which belongs to the early Cambrian. Geochemical characteristics show that the content range of SiO2 is large, and with the high Al2O3、P2O5, low TiO2 、 MnO、 CaO characteristic, A/CNK=0.89 ~ 2.04, with the weak peraluminous to peraluminous features, Na2O+K2O=4.3%~8.67%, these features indicates that the Keketale pluton belongs to calc-alkaline peraluminous granite. Total content of rare earth elements is lower, more fractionation between LREE and HREE, and evidently negative anomaly in Eu, the rare earth elements patterns with LREE enrichment and HREE loss is right dip type. The relative enrichment in lithophile element, relative depletion in high field strength elements are similar to the magmatic features of subduction zone. As a whole, it has been influenced by the presence of island arc subduction. The source of the Keketale pluton may be the magma which formed by the remelting of the crust. The tectonic background of the Keketale pluton is related to subduction.Sinian Fuyun terrain is mainly composed with plagioclase biotite quartz schist, biotite plagioclase schist, two-mica quartz schist, plagioclase actinolite schist, biotite plagioclase gneiss and two-mica plagioclase gneiss. The stratigraphy is redefinited as Sinian Fuyun terrain but not upper Carboniferous Karaertix group which definited by the previous studies. Different degrees of deformation and metamorphism occurred in the rock, and metamorphic grade is up to granulite facies.The structural features of Keketale pluton and Sinian Fuyun terrain are complex, including ductile deformation at deep level and the brittle deformation at shallow level.