Characteristics And Genesis Of The Xiaoling Cycle Volcanic Rocks In West Huanren

The volcanic rocks of Xiaoling Formation in Early Cretaceous have a wide distribution in Huanren area,Liaoning.The research of this area is helpful to reinforce the space-time evolution of magmatism in Mesozoic.The paper's content is the characteristics and genesis of the Xiaoling cycle Volcanic rocks in west Huanren.It analyzed the characteristics of petrology,geochemistry and chronology,and summaried several conclusions:The volcanic rocks of Xiaoling Formation are mainly andesite,dacite,rhyolite,rhyolitic pyroclastic rocks and andesite pyroclastic rocks,which belong to the high-K calc-alkaline and shoshonite series.The zircon U-Pb dating result of vocanic rocks is 128±1 Ma,indicating that acid volcanic rocks of Xiaoling Formation were formed in Early Cretaceous.The characteristics of volcanic activity can be divided into 4 levels:the ? Level is called volcanic eruption cycle;the ? Level is the stage of magma evolution;the? Level is the intermittent stage of volcanic activity;the ? Level i(?)the rhythm of volcanic eruption.The intermediate and intermediate-acidic volcanic rocks of Xi-oling Formation have the similar characteristics of trace elements and rare earth elements,it indicates that the magma origin of the intermediate and intermediate-acid volcanic rocks are related to the subduction,the primitive magma is rising by the subduction zone fluid metasomatism of overlying mantle formed by partial melting,reduce sediment melt to join,and in the process of magma rising has experienced a certain degree of crustal contamination and high separation and crystallization.The acidic volcanic rocks derive from the partial melting of the cruse,and in the process of magma rising has experienced a certain degree of crustal contamination.Comprehensive analysis shows that the volcanic rocks of Xiaoling Formation were produced by magma activity in extensionnal setting within plate and the characters of arc volcanic rocks of anorogenic environment.The power of volcanic rocks are originated from the subduction of the Pacific plate to the Eurasian plate.