Regional Correlation Of The Kangbutiebao Formation And Its Ore-Bearing Propertiesin Atthe Southern Margin Of Altai,Xinjiang

The Early Devonian Kangbutiebao Formation is widely distributed in the southern margin of Altay,Xinjiang,which is the most important ore-bearing strata in the Altai metallogenic belt.This paper takes the Kangbutiebao Formation as the research object,and based on a large amount of previous research results and field geological surveys,determines its formation age,studies the source characteristics,genetic mechanism,forming environment and geological structure of volcanic rocks,discusses the stratigraphic framework and tectonic environment,and summarizes the regional variation law.The aim is to provide detailed basic data of regional comparison for the research work of the main structure-stratigraphic zone in the Altay area.Comprehensive regional geological background and previous research results,discuss the Paleozoic tectonic evolution in Altay area.Zircon U-Pb ages of 394±1Ma and 402.72±0.92 Ma were obtained from the rhyolite of the Kangbutiebao Formation.The rocks are enriched in large ion lithophile elements(Rb,Th,U)and high field strength elements(Zr,Hf),and depleted in elements(Ba,Nb,Ta,Sr,Ti),showing the characteristics of arc volcanic rocks under subduction.The value of ?Hf(t)is4.16?11.08,indicating that the volcanic rock material of this formation is derived from the newborn crust.The rock assemblage,geochemistry,contact relationship,and age characteristics of the Kangbutiebao Formation in the three volcanic-sedimentary basins of Chonghuer,Kelang,and Maizi on the southern margin of Altay are analyzed and studied.The Kangbutiebao Formation is a set of acidic volcanic rock-pyroclastic rock series,which can be divided into upper and lower sections.The lithology of the lower section is dominated by clastic rocks with volcanic rocks,and the lithology of the upper section is dominated by volcanic rocks with clastic rocks.Compared with the other two basins,the rock deformation and metamorphism of the Chonghuer Basin is more intense.Geochemical comparison shows that the three basins have similar characteristics of major elements.The characteristics of rare earth and trace elements indicate that the Kangbutiebao Formation forms a continental marginal arc environment on the active continental margin.The Kangbutiebao Formation in the three basins is in unconformity or fault contact with the overlying Altay Formation,and is in fault contact with the underlying Kulumuti Formation.The isotope age of this group in the Chonghuer Basin is concentrated in 385-405 Ma;the age of this group in the Kelang Basin is concentrated in 388-412 Ma;the age of this group in the Maizi Basin is concentrated in394-410 Ma.The times are consistent.The Kangbutiebao Formation is generally comparable in these three basins.Most of the deposits(including lead-zinc deposits,copper deposits,and iron deposits)that occur in the Kangbutiebao Formation are based on the characteristics of strata-controlled deposits.Most deposits occur in pyroclastic or sedimentary rocks in the eruptive interstitial.The source of ore-forming material is closely related to volcanic activity.