The Study Of Goechronology And Geochemistry Of Late Paleozoic Volcanic Rocks Of Kelang Volcanic-sedimentary Basin, Altay Mountains, Xinjiang

The Late Paleozoic volcanic rocks of Altay Kelang basin exposed at the southern marginof the Altay, and is located in the joint position between the Siberian plate andKazakhstan-Junggar plate, and is also the important record of tectonic evolution of Altayregion. The Lower Devonian volcanic rocks of Kangbutiebao Formation develops within thisregion is not only focus on transformation for the Altay orogen tectonic system but alsoclosely related with mineralization. Therefore, meticulous research on the volcanic rocks ofKangbutiebao Formation within Kelang basin has important scientific meaning for betterunderstanding the process of tectonic evolution of Altay orogen. At the same time, it alsoprovides basic geologic information on Late Paleozoic volcanic metallogenic background. Onthe basis of previous research,this text focus on identifying the combination, spatial andtemporal distribution and variation of volcanic rocks, and divided volcanic eruption cycles,the establishment of regional volcanic geochronological framework to explore the propertiesof volcanic tectonic formation.In order to complete this task, this article studiesKangbutiebao volcanic of Lower Devonian Series within Kelang basin by combiningpetrology, geochemical, geochronology with the achievement of palaeobiology. Obtain thefollowing understanding:1、Kangbutiebao Formation within the Kelang basin composed with acidic volcanicrocks-pyroclastic rock-carbonatite,but Volcanic eruption-sedimentary cycles wereregionally different. Volcanic eruption was mainly the volcanogenitic sedimentary-extrusivfacies early and explosive-volcanogenitic sedimentary facies later.The type of rockassociation in this area is complete. The super-stratum was mainly composed with acidicvolcanic rocks and volcanic rocks; the mid stratum was mainly composed with Carbonaterocks, felsic volcanic, volcaniclastic rocks and the sub stratum was mainly composed withchondro-clasolite, volcanic rocks.2、Kangbutiebao Formation within the Kelang basin overthrusted on the Middle-UpperDevonian Altaizhen Formation had a clear top interface and a ductile shear belt on theSilurian strata. The zircons with well-defined oscillatory zoning from volcanics samplesyielded mean206Pb/238U ages of389Ma~412Ma,which are interpreted as the age of Kangbutiebao Formation.3、Volcanics are high in concentrstions of SiO2and total alkali(Na2O+K2O),and lowerconcentrstions of Al2O3、CaO、MgO,and they have the differentiation trend of calc-alkalinevolcanic rocks. Nb and Ta and Zr and Hf undergone significant differentiation, U, Th contentsand Th/U ratio is much larger than the primitive mantle; Ti/Zr=4.2~7.2<20,suggesting thatthe rocks originated from the partial melting of crust.4、The volcanic rocks of the Kelang basin are generally enriched in LREE and LILE, andrelatively depleted in HREE and HFSE, have obvious Nb,Ta and Ti negative anomalies.Therefore, they show the geochemistical characteristics of epicontinental island arc relatedwith subduction action.