Geochronology,tectonic setting and mineralization of granitoids in Jueluotage area,eastern Tianshan,Xinjiang
Geochronology,tectonic setting and mineralization of granitoids in Jueluotage area,eastern Tianshan,Xinjiang
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作者：
Z. Tao
新疆铁纳山东部觉罗塔格地区分布着大量的岩浆岩，其中以花岗岩为主，以往对这些花岗质侵入岩的研究较少。本文对该区主要花岗质深成岩体的地质特征进行了研究，并用锆石LA-ICPMS U-Pb法系统地测定了它们的同位素年龄。镜儿泉岩体376.9±3.1 Ma，西峰山岩体349.0±3.4 Ma，石鹰滩岩体342±11 Ma，长条山岩体337.4±2.8 Ma，天目岩体320.2±3.1 Ma，白灵山岩体317.7±3.7 Ma，白石泉岩体303±18 Ma，地坎岩体288.0±2.5 Ma，黄山岩体288±17 Ma，白山洞岩体303±18 Ma，官岛岩体284.1±5.8 Ma，红石岩体282.7±4.2 Ma，龙洞岩体276.2±2.5 Ma，多头山岩体271.7±5.5 Ma。双岔沟岩体252.4 Ma±2.9 Ma，土墩岩体246.2 Ma±2.6 Ma。这些年龄数据为研究本区岩浆活动与构造演化的成因关系以及深部动力学过程提供了重要的信息和依据。本文结合前人已知的该区花岗质岩体年代学资料，将觉罗塔格花岗质岩体的侵入和结晶时间框架限制在386~230 Ma之间。花岗岩类岩浆活动可划分为泥盆纪晚期(386.5~369.5 Ma)、早石炭世(349~330 Ma)、晚石炭世-晚二叠世阶段(320~252 Ma)和中三叠世阶段(246~230 Ma)，前三期花岗岩活动持续时间较长，强度较大，第三期在本区达到顶峰，第四期岩浆活动变弱且分散。从哈尔滨-丹南湖岛弧带到阿齐山-雅曼苏岛弧带，再到康古尔-黄山韧性剪切带，花岗岩类侵入年龄逐渐年轻化，花岗岩类也呈现出从研究区东部到研究区中西部再到韧性剪切带的年轻化趋势。根据后碰撞理论和中亚、北疆造山的研究成果，花岗岩类岩浆活动与研究区的构造演化具有密切的关系。本区岩浆活动经历了前碰撞阶段、碰撞后阶段、碰撞后阶段和板内阶段，与花岗岩类的四个时间阶段完全对应，大部分花岗岩类形成于碰撞后阶段。觉洛区四期花岗岩类成矿作用从无明显成矿开始，到斑岩铜矿和火山岩铁矿床，再到韧性剪切带型金矿床和夕卡岩型银(铜)矿床。受碰撞地球动力学作用控制的斑岩型铜矿床和受碰撞后地球动力学作用控制的韧性剪切带型金矿床是研究区花岗岩类的主要成矿类型。本文系统阐述了觉罗塔格地区花岗岩类的时空分布特征及其与构造演化和成矿的关系，为进一步研究新疆北部晚古生代特别是后碰撞阶段的岩浆演化和成矿作用提供了坚实的基础。
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.