Geochemistry And Tectonic Significance Of Jianggeerkuduke Pluton In Northern East Junggar,Xinjiang

Junggar orogenic belt in eastern Xinjiang is an important part of the central Asian orogenic belt,and it is a typical accretive orogenic belt formed by subduction accretive complex,ophiolite and magmatic arc formed during the evolution of Paleozoic Asian ocean.It is located in the combination of Siberian plate and Junggar plate in Kazakhstan.Magmatic rocks from early Paleozoic to late Paleozoic are widely exposed in fuyun county,northern east Junggar.Predecessors have done a lot of research work on single rock mass,especially late Paleozoic rock mass.However,there is a lack of comparative study on the early Paleozoic to late Paleozoic rock mass systems.Therefore,systematic comparative study on petrology,chronology and petrochemistry of early Paleozoic magmatic rocks in this area plays a key role in restoring the formation process of the eastern Junggar orogenic belt,which is of great significance for studying the tectonic evolution in this region.This paper focuses on the early Paleozoic magmatic rocks in the south of Fuyun county,northern east Junggar,Xinjiang.Through detailed studies on petrography,geochemistry and isotopic chronology of jianggeekuduk rock mass in this area,the emplacement age of this rock mass is determined,and its geochemical characteristics,genesis and tectonic background are preliminarily discussed.Combined with previous data,the Paleozoic magmatic rocks and tectonic evolution in this area are briefly discussed.Using LA-ICP-MS zircon U-Pb isotopic dating method,the average age of quartz diorite is 432.8 ± 2.7 Ma.According to the latest internationally divided Ordovician and Silurian plans,the emplacement time of quartz diorite should be early Silurian.It is believed that the early Silurian quartz diorite was diagenetic environment with high temperature and pressure,which can be attributed to the continental crust thickening,lithospheric root detachment and subsidence caused by continental-continental collision after ocean basin closure,and the subsequent extension and underplating of mantle-derived magma.The huge heat energy provided by the underplating mantle-derived magma partially melted the overlying primary lower continental crust-High potassium metamorphic basalt,producing quartz diorite magma,while the garnet-bearing granulite facies minerals remained in the source region.The preliminary discussion divides the tectonic evolution in the study area into seven stages: early continental margin tension in early Paleozoic,early-middle oceanic land conversion in early Paleozoic,development of the Ereqisi oceanic basin in late Paleozoic and extension of theKubusu back-arc basin in late Paleozoic,early-middle oceanic land conversion in late Paleozoic,intraplate extension in late Paleozoic,intracontinental overlapping orogeny in late Permian-Triassic,intracontinental basin formation and orogeny uplift in meso-cenozoic.