Study On Geochemical Characteristics And Tectonic Environment Of Early Paleozoic Volcanic Rocks In Guozigou Area,Northern Margin Of Yili Basin,Xinjiang

The study area is located in the Guozigou area on the northern margin of the Yili Basin.It is a structurally active belt on the northern margin of the Yili block.Its diagenesis is controlled by the subduction and subduction of the Northern Tianshan Ocean Basin to the north.This paper takes the early Paleozoic volcanic rocks in the Guozigou area on the northern margin of the Yili Basin as the research object,focusing on the detailed statistical analysis of the petrology and petrogeochemistry of the volcanic rocks in the study area.The fuzzy clustering method is used to analyze the collected geochemical data of volcanic rocks in the study area.At the same time,a mathematical model and flow chart are established to simulate the analysis process.Through the design of the mathematical model solving process through the Python programming language,and the efficiency of comprehensive analysis and processing of data is improved.In-depth analysis of the inherent geological meaning of volcanic rock geochemical data,and comprehensively summarize the early Paleozoic volcanic rock petrology,rock assemblage,and petrogeochemical characteristics of the study area.Combining with the research results of previous people in the area on sedimentation,intrusive magmatism,metamorphism,etc.,an in-depth discussion on the regional tectonic background of the Early Paleozoic in the study area is carried out.The regional tectonic evolution model was established,and the early Paleozoic crustal accretion process in the northern part of the West Tianshan was established.It provides a new conceptual model and data support for regional geological prospecting and multi-element investigation and research of natural resources.The time limit of early Paleozoic volcanic activity in the study area is mainly concentrated in the Middle Ordovician,Late Ordovician,and Early Silurian.Volcanic lava and homogeneous pyroclastic sedimentary rocks are produced in the form of unstable interlayers or lenses,which occur in sequence in lithostratigraphic units such as the Nailengele Daban Formation,Huduke Daban Formation,and Nilekehe Formation.The volcanic rocks of the Middle Ordovician Nailengledaban Formation are mainly intermediate and acidic lavas.The rocks are rich in aluminum and poor in magnesium.They belong to the high-potassium volcanic rock series.The study of rock geochemistry shows that the large ion lithophile elements such as Th and Ta are strongly enriched in the rock,and the high-field elements such as Nb,Sr and Ti are weakly depleted.According to the brachiopod fossil species in the stratigraphic limestones of volcanic rocks,it is believed that the main body of this set of volcanic rocks was formed in the Middle Ordovician.The Upper Ordovician Hudukedaban Formation volcanic rocks are dominated by intermediate-acid pyroclastic rocks,belonging to the series of high-potassium calc-alkaline rocks.Rock geochemical studies have shown that the rocks are strongly enriched with large ion-philic elements such as Ba,K and Sr.Significant loss of high field strength elements such as Y,Nb,and Ti.The rare earth element characteristics of this group of volcanic rocks are similar to the distribution of rare earth elements in typical subducted acidic volcanic rocks.The volcanic rocks have the geochemical characteristics of arc volcanic rocks.According to the coral fossil species in the stratigraphic limestones in the volcanic rocks,it is believed that the main body of the volcanic rocks was formed in the Late Ordovician.The Lower Silurian Nilekehe Formation volcanic rocks are mainly composed of a set of intermediate-basic volcanic rocks,belonging to the calc-alkaline series.The study of rock geochemistry shows that the rocks are rich in large ion lithophile elements such as Rb and Th,and obviously depleted of high field strength elements such as Ba,Ti,and Y,which generally show the characteristics of typical active continental margin arc volcanic rocks.Based on the species of graptolite fossils in the stratigraphic sedimentary rocks of the volcanic rocks,it is believed that the main body of this set of volcanic rocks was formed in the Early Silurian.Fuzzy clustering method was used to calculate fuzzy mathematics between 16 volcanic rock samples and standard volcanic rock geochemical data in the study area,and to compare and determine the membership degrees of volcanic rock samples from the Nailengele Daban Formation,Huduke Daban Formation,and Nilekehe Formation.The values are 0.67,0.58,and 0.67.It is concluded that the Middle and Late Ordovician volcanic rocks were formed in the Japanese island arc environment,and the Early Silurian volcanic rocks were formed in the Mariana island arc environment.Therefore,based on the systematic combing and analysis of the early Paleozoic volcanic rocks in the study area,it is believed that the three-stage volcanic rocks may have formed in the active continental margin arc tectonic environment.Based on previous research results,a new early Paleozoic regional tectonic evolution model on the northern margin of the Yili block is proposed.It is believed that the early Paleozoic crustal growth in this area is related to the continuous southward subduction of the North Tianshan-Kanggur Ocean to the north,and the Early Paleozoic Volcanic rocks are the result of crust-mantle interaction during oceanic crust subduction.