Research On Geochemical Characteristics Of Carboniferous Volcanic Rocks In Malang Sag Of Santanghu Basin

This study is the use of core observation,thin section of the polarizing microscope,the element characteristics of volcanic rocks in Malang depression,Santanghu basin.And summed the Malang depression of Santanghu Basin in which tectonic environment through the diagram.The volcanic rocks of this area are mainly neutral rocks and mafic,there are also a few alkaline series rocks.This area developed lava and pyroclastic rocks:The lava class include three categories of seven types Basalt.They are basaltic andesite,trachyte,basalt,basaltic trachyandesite,andesite,trachyandesite rock and trachyte.Pyroclastic rocks contain fusion bonded volcaniclastic rocks,pyroclastic rocks,volcanic breccia,tuff,since broken,shen volcanic breccia,tuff and tuffaceous mudstone.The area carved out of 34 kinds of rock types.The rare earth elements are right inclined because they are strongly enriched in LREE.Ce anomaly and Eu anomalies are not obvious.That the magma of the volcanic rocks have not experienced significant plagioclase crystallization separation of the role and source of enriched mantle.The large ion lithophile elements like Rb,Sr,Ba content is significantly higher.Zr,Nb,Ti negative anomalies.The Nb content is low and Zr content is significantly higher.So Zr/Nb is higher.These features suggest that the volcanic of the district crust-mantle mixing.The tectonic environment diagrams shows that Malang Sag volcanic rocks formed in an intraplate extensional tectonic setting and tectonic setting of the volcanic arc superimposed and it was transformed by mantle fluids and magmatism.According to the microscope for naming the volcanic rocks of this district.Through the TAS diagram and constant element's correlation diagram to consolidate statement of the composition of volcanic rocks and chemical classification naming.Furthermore,use the spider diagram and REE diagrams to distinguish between a series of rock composition and magma evolution.Use the diagrams of major and trace elements and REE to jointly study the tectonic environment of this area.