Spatiotemporal Evolution Of Mesozoic Volcanic Rocks In Chengdao-Zhuanghai Area

In recent years,with the increasing energy demand and the continuous expansion of oil and gas exploration,people gradually realize that volcanic rock can also form a good accumulation area of oil and gas,so volcanic rock oil and gas reservoirs gradually become an important area for oil and gas exploration.The research degree of Mesozoic volcanic rocks in chengdao-zhuanghai area involved in this paper is low.How to correctly divide and contrast the stratigraphic sequence of volcanic rocks in the study area and establish the stratigraphic framework of volcanic rocks is an important basis for the exploration of volcanic rocks in this area.The paper based on core,thin section,logging,seismic,analysis and laboratory data,firstly,this paper studies the lithology and petrographic characteristics of volcanic rocks in the study area.The longitudinal variation of lithology in different eruption periods is an important basis for the classification of volcanic eruption cycles and periods.Secondly,based on the division of single well cycle times and the comparison and closure of skeleton connected well profiles,the plane distribution characteristics of each cycle times in the whole region were determined.Finally,the eruption time and eruption environment in the study area were analyzed.By means of core observation,thin section identification and geochemical analysis,35 rock types of 5 categories were determined in chengdao-zhuanghai area based on the diagenetic mode of volcanic rocks and the content of pyroclastic material.Lava know from TAS diagram in the alkaline and alkaline both series development,with crude andesite basalt,andesite,dacite,basalt,volcanic clastic lava mainly breccia lava and ash coagulation lava,pyroclastic rock in basaltic/andesitic breccia and tuff,heavy volcanic clastic rocks in the study area is given priority to with low limestone,kind of volcanic rocks in this area has a small amount of times Mr Andreessen porphyrite development.The petrographic classification of volcanic rocks is mainly based on the volcanic eruption mode,rock type and volcanic rock production form and characteristics.The volcanic rocks in chengdao-zhuanghai area are divided into four types:eruptive facies,overflow facies,subvolcanic facies and volcanic sedimentary facies.In addition each phase and the subdivision,outbreaks are further divided into empty fall and facies and heat clastic flow subfacies,and overflow facies is divided into upper and lower subfacies,the volcanic phase including the volcanic facies,volcanic sedimentary facies include contain clastic volcanic sedimentary subfacies,therefore the volcanic facies in the study area is divided into four and six subfacies.The plane distribution characteristics are similar to the lithology,and the fault also plays an important control role in the distribution of the lithofacies in this area.The overflow phase is mainly distributed near the fault,while the outburst phase is more likely to develop in the joint part of the fault.Volcanic sedimentary facies are mainly distributed in the combination of northwest and southeast regions and the periphery of the overflow facies.The classification of volcanic rock cycle is based on the identification of lithologic facies and interface.Based on the classification results of lithology and lithofacies and the identification of the interface of cycle periods,this paper divides the cycle periods of this area by combining logging curves and seismic reflection characteristics.The research area is divided into two cycles and six phases,the first cycle from bottom to top is divided into two phases,and the second cycle is divided into four phases.The distribution of the first cycle is mainly concentrated in the sag zone,which plays a role of filling and leveling in this area.Until the next cycle of district began to accept deposits,bottom-up periods time thickness regions were located in the northwest 30 Wells in 11 to Ken Ken east east and southeast area around 231,reflects the distribution of volcanic rocks in the study area is mainly divided into two major development zone of northwest and southeast,may represent the region two volcanic eruption place,besides major boundary fault plays an important role in the region,the thickness of the regional general cross location near the fault or fault.In order to determine the age and tectonic environment of volcanic rocks in this area,samples were collected for u-pb dating of LA-ICP-M zircon and principal trace element analysis.The u-pb age of la-icp-ms zircons obtained from andesite is(104±1)Ma.The tectonic environment of volcanic rocks in the study area was determined to be arc island-orogenic belt environment by TAS map,trace element analysis and analysis results and trace element tectonic environment map...