Petrological Characteristics And Volcanic Structure Analysis Of The Middle Jurassic In The Bajiazi-Pingshan Area Of Acheng

The Middle Jurassic volcanic rocks in Bajiazi-Pingshan area of A'cheng are located in the Bindong uplift belt of the Songnen massif.There is widespread volcanism and have undergone complex geological evolution in this area.However,the study of volcanic petrology and volcanic structure is still weak.In this paper,I present detailed studies of the field observations,petrology,and geochemistry for Middle Jurassic volcanic rocks in the Bajiazi-Pingshan area of A'cheng.The volcanic rocks in this area are composed of NE-trending Middle Jurassic Tai'antun period volcanic rocks,which can be divided into:(1)Middle Jurassic volcanic rocks,including andesite,basalt andesite,dacite,and trachyte;(2)Middle Jurassic volcaniclastic rocks,including andesitic debris crystal tuff,dacitic clastic breccia tuff lava,sodium trachyte tuff and sodium trachyte vitreous clastic tuff.The volcanic rocks in the study area were founded in Tai'antun,Shangzhi City in1967 by Wang Dan Group.The contact relationship between volcanic rocks and intrusive rocks was discovered in the field,and previous studies on volcanic rock chronology were carried out.Therefore,the age of volcanic rocks in the Antun period was determined to be Middle Jurassic.At present,the volcanic structures in the study area are only classified into grade I and II.On this basis,this paper further classifies grade III,IV and V according to volcanic facies,eruption cycle and rhythm.The Jiamusi-Shangzhi volcanic eruption zone is of grade III volcanic structure,the Beiyaoling volcanic structural basin and Laoshi Xinggou volcanic structural basin are of grade IV volcanic structure,and the Laoshi Xinggou South 508 volcano and Daqingshan 495 volcano are of grade V volcanic structure.