Geochemistry And Tectonic Significance Of Carboniferous Volcanic Rocks In Yamansu Area,Eastern Tianshan,NW China

The central Asian orogenic belt(CAOB),is a "global giant ore-forming field" and a "natural laboratory" for studying global continental dynamics and continental metallogenic theory.The eastern Tianshan area was in the main tectonic activity period in the Late Paleozoic,especially the Carboniferous to Permian.During this period,a large number of magmatic activities were developed in the area,and a large area of magmatic rock was distributed.These magma events can provide important information for tectonic events such as subduction and erosion of the Tiantian Mountains in the eastern Tianshan Mountains,plate aggregate collisions and subsequent collisional plate stretching.This paper takes the Carboniferous volcanic rocks in the Yamansu area as the research object.Through the geochemical characteristics of the rocks,combined with the previous research results and regional tectonic setting,the genesis and tectonic evolution process and environment of the Carboniferous volcanic rocks in the Yamansu Island arc are revealed.On the basis of collecting the research results of the study area and its adjacent areas in detail and combining with my actual field research experience,this paper analyzes and studies the volcanic rocks in three typical strata in the study area.At the same time,the Carboniferous tectonic environment and its evolution characteristics of the Yamansu island arc belt are illustrated by using continental dynamics and continental metallogenic theory,and the following recognition is obtained:1.The Aqishan Formation of the study area is constructed as a group of marine volcanic rocks,and the formation period should be Early Carboniferous;The Yamansu Formation is a group of volcanic-sedimentary deposits in the near-volcanic sedimentary basin,which was formed in the late Early Carboniferous period;The Tugutubulak Formation is a group of volcanic arc volcanic-sedimentary rock formations;At the same time,the zircon U-Pb age value measured in this group was303.87 ± 5 Ma,and it was judged that the formation period should be the LateCarboniferous period.2.In terms of petrogeochemistry,Early Carboniferous volcanic rocks are characterized by typical island arc volcanic rocks.The Late Carboniferous volcanic rocks are formed in the continental margin arc environment.It shows that there is a structural transformation process in the Early Carboniferous-Night Carboniferous.3.Combining regional research results,The study concludes that:Early Carboniferous Kanggur Ocean Basin subducted to both sides.The Dananhu composite island arc belt and the Carboniferous Aqishan-Yamansu island arc belt were formed.In the early Late Carboniferous,it was further inhomogeneous stretching on the basis of back-arc basins.In the late Late Carboniferous,the ocean basin was basically closed.It may be a residual ocean basin and a Congulian melange belt is formed in the northwestern part of the study area.