Volcanics Geochemical Behavior Study In Yingcheng Formation Of The Northern Songliao Basin

In the paper,various methods,such as the core observation,the identification and analysis of microscope thin sections,geochemical element characteristics of volcanic rocks,are comprehensively used to intensively study the geochemical characteristics of the volcanic rocks in Yingcheng Formation of the northern Songliao Basin, otherwise new methods are concluded to identify volcanic rocks through experiments.The volcanic Yingcheng acidic volcanic rocks, followed by neutral rocks and basic rocks.They are calc-alkaline rocks, sub-alkaline rocks and also calcium, alkaline rocks and alkaline rocks.There are two types of lava and pyroclastic rocks. The former include rhyolite, dacite, trachyte, andesite and basalt ;the latter including agglomerate lava, brecciated lava, tuff lava, agglomerate, volcanic breccia, tuff, sed-volcanic pyroclastic rocks and pyroclastic sedimentary rocks, etc., were divided into more than 23 kinds of rock types .The large ion lithophile elements Rb, Sr and Ba were significantly higher in Yingcheng. The content of Nb is lower ,and the content of Zr is significantly higher, therefore the Zr/Nb is larger.These features indicate that volcanic rocks are the result of crust-mantle mixing. By tectonic discrimination diagrams show that the volcanic rocks formed in Yingcheng extensional plate tectonic setting of Early Cretaceous in eastern Chinese large-scale lithospheric thinning and magmatism.Identification of volcanic rocks by the tests showed that different types of volcanic rocks on the geochemical elements in a more statistically significant with the law.It summarizes the distinction between lava and pyroclastic rocks of zirconium yttrium series plate method; distinction between basalt, andesite, dacite, trachyte and rhyolite in the TAS diagram and major element plate binding assay;distinction between agglomerate rocks, volcanic breccia and tuff trace + REE plate method.