Geochronology,tectonic setting and mineralization of granitoids in Jueluotage area,eastern Tianshan,Xinjiang

There distributes a lot of magmatic rocks,most of them are granitic rocks in the Jueluotag area,eastern Tisnashan, Xinjiang.The previous research on these granitic intrusions is inadequate.In this work,the geological characteristics of the major granitic plutons in the area have been investigated,and their isotopic ages are systematically dated through the zircon LA-ICPMS U-Pb method.The precise age data of the 16 granitic plutons are as follows;Jingerquan pluton 376.9±3.1Ma,Xifengshan pluton 349.0±3.4Ma,Shiyingtan pluton 342±11 Ma,Changtiaoshan pluton 337.4±2.8Ma,Tianmu pluton 320.2±3.1Ma,Bailingshan pluton 317.7±3.7Ma,Baishiquan pluton 303±18Ma,Dikan pluton 288.0±2.5Ma,Huangshan pluton 288±17Ma,Baishandong pluton 303±18Ma,Guandao pluton 284.1±5.8Ma,Hongshi pluton 282.7±4.2Ma,Longdong pluton 276.2±2.5Ma,Duotoushan pluton 271.7±5.5Ma,Shuangchagou pluton 252.4±2.9Ma and Tudun pluton 246.2±2.6Ma.These age data provide important information and bases for the investigations of genetic relation between the magmatic activities and the tectonic evolution in this area,as well as with the deep dynamic processes.Combined with some known chronological data of the granitic plutons in this area from other workers, this article has constrained the intrusion and crystallization time framework of the granitic plutons in Jueluotage to be between 386Ma and 230Ma.The granitoid magmatic activity can be divided into four stages,which are the Late Devonian stage(386.5～369.5Ma), the Early Carboniferous stage(349～330Ma),the Late Carboniferous to Late Permian stage(320～252Ma) and the Middle Triassic stage(246～230Ma).The early three stages of the granitoid activities tend to be lasting longer and more intense from the first to the third stage,and the third stage reached the peak in the area,and the magmatic activities in the forth stage became weak and scattered. The intrusion ages of the granitic plutons became younger from Haerlike-Dannanhu island arc belt,to Aqishan-Yamansu island arc belt,then to Kangguer-Huangshan ductile shear zone,and the granitoids also showed a youngering trend from the east of study area to the mid-west of study area,then to the ductile shear zone.Based on the post-collision theory and the results for the orogeny of Central Asia and northern Xinjiang,there display affinitive relationship between the granitoid magmatic activity and the tectonic evolution in the study area.This article further proposes a model for the evolution of granitoids in Jueluotage area;The magmatic activity in this area had undergone through the pre-collisional stage,the collisional stage,the post- collisional stage and the within-plate stage,which completely correspond with the four temporal stages of granitoids,and most of granitoids formed in the post- collisional stage.In jueluotage area,the mineralization with the four stages granitoids started from no obvious mineralization,to the porphyry copper deposits and volcanic iron deposits,then to the ductile shear zone type gold deposits and skarn-type Ag(Cu) deposits,lastly to the porphyry quartz veins deposits.The porphyry copper deposits controlled by the collisional geodynamic process and the ductile shear zone type gold deposits controlled by the post-collisional geodynamic process are the main mineralization types with granitoids in the study area This work systematically expatiated the granitoids in Jueluotag area with the characters of temporal and spatial distribution, the relationships with the tectonic evolution and mineralization,which supplied a solid foundation for further research on the magmatic evolution and mineralization in Late Paleozoic,especially in the post- collisional stage in northern Xinjiang.