Genetic Types And Geological Significance Of The Wunuer Siliceous Rock In Inner Mongolia

Wunuer is located in the Greater Khingan Range arc basin system of Tianshan-Xingmeng orogenic system.In this paper,two groups of siliceous rocks with different output characteristics were found in the field,one kind along with ophiolitic melange distributed along the collage belt,and the other associated with the island arc volcanic rocks.Through the comprehensive analysis of its field characteristics,petrology and geochemical methods,the information of the source and sedimentary environment of the two kinds of siliceous rocks has been obtained,which enriches the basic geological data of the study area.Two different types of siliceous rocks are exposed in the study area.The first type of siliceous rock is produced in the basalt,or occurs in the metamorphic basalt,which is mostly gray and dark gray green,and partly because of the high manganese content in the dark purple,with more radiolarian,the gray yellow siliceous rock and the very thin layer of mud siliceous rocks,the horizontal bedding development and the chip cryptocrystalline structure.The second species are associated with acidic and acidic island arc volcanic rocks,and the vertical sequence is characterized by gray green fine sandstone-Green siltstone-sily(tuff)siliceous rock-Green siliceous rock.The overall manifestation is the rhythmic characteristics of the upward deepening,few radiolarian.The silicon content of the two siliceous rocks is generally low,and the mineral composition is mainly cryptocrystalline-microcrystalline quartz.The ³⁰Si distribution of siliceous rocks associated with ophiolitic melange is-0.1‰?0.1‰,with an average of-0.1‰,and the ¹⁸O value is 4.4‰?5.8‰.?REE is low,and the abundance of trace elements is lower than the Clark value,which indicates that the water body formed by the siliceous rock is deeper.Some samples have biogenic characteristics such as high silicon and high iron.The siliceous rocks associated with intermediate acid and acidic volcanic rocks are of ³⁰Si value of 0.1‰and ¹⁸O value of 10‰.The origin of igneous rock is obvious,and the source of siliceous rock is mainly magmatism.Geological,petrographic and geochemical characteristics indicate that the siliceous rocks associated with ophiolitic melange are formed in the back arc expanding oceanic basin.The siliceous rocks associated with intermediate acid and acidic island arc volcanic rocks are located on the island arc zone of the Duobaoshan island.The siliceous mainly originates from the volcanism,and the siliceous rocks contain more condensate,and the tectonic environment is an inter arc basin.