三江造山带北段扎河岩体锆石LA-ICP-MSU-Pb年龄及其地质意义  

LA-ICP-MS Zircon U-Pb Ages of the Zhahe Pluton in North Part of Sanjiang Orogenic Belt and Its Geological Significance

作　　者：马俊强 张运昌 陈根[1] 纪国忠 廖强[1] 杨晓君 

机构地区：[1]四川省核工业地质调查院,四川成都610000

出　　处：《西北地质》2017年第4期70-80,共11页Northwestern Geology

基　　金：中国地质调查局地质调查项目"青海省治多县俄昌公仁地区1:5万I46E012020;I46E013020;I46E014020三幅区域地质矿产调查"项目(12120113033500)

摘　　要：扎河岩体产出于三江造山带北段可可西里-金沙江缝合带,呈北西向展布,受北西向断裂构造控制。笔者通过详细调查,在石英闪长岩锆石中获得的(190.4±2.8)Ma的年龄值,在富石英英云闪长岩锆石中获得的(192.1±1.2)Ma的年龄值,基本反映了扎河岩体成岩于早侏罗世,表明金沙江结合带经受了该时期构造-岩浆活动的影响。稀土元素特征表明该套侵入岩属轻稀土富集、重稀土平坦型,具有弱正Eu异常,反映岩石经历了一定程度的分离结晶作用,微量元素显示出活动大陆边缘岛弧岩浆的特征,笔者通过野外地质调查,结合区域构造演化,认为侏罗纪早期三江北段已进入碰撞后陆内汇聚阶段,该期构造-岩浆事件的发生是受班公湖-怒江洋向北俯冲消减持续影响效应的产物。The Zhahe pluton is located in the north part of the Sanjiang Orogenic Belt, with NW trend, which is controlled by NE direction fault. According to the detailed survey, the obtained zircon UPb ages of quartz diorite and tonalite are （190 4±2 8） Ma and （192 1±1 2） Ma, respectively, indicating that the Zhahe pluton was formed in Early Jurassic. The dating result suggests that the Jinshajiang suture zone was affected by the tectonic magmatic activity in this period. On the chondrite normalized REE diagram, this pluton is enriched in LREE and has a flat HREE pattern. The slight negative anomaly of Eu indicates that this pluton experienced a fractional crystallization of plagioclase. The trace element distribution of this pluton is similar to the ones of island arc magma.Based on the geochemistry and petrography characteristics mentioned above, its concluded that the Zhahe Pluton has affected by the subduction component and it might be formed in a tectonic compression island arc or active continental margin.After analyzing the field geological survey and regional tectonic evolution, its believed that the north part of Sanjiang Orogenic Belt had entered the stage of intracontinental convergence in Early Jurassic Period, and that this tectono magmatic event has affected by the northwardsubduction of Bangong LakeNujiang Ocean and serves as the product of this sustained tectonic effect.

关 键 词：造山带 扎河岩体 锆石LA-ICP-MSU-PB年龄 地球化学 

分 类 号：P597[天文地球—地球化学]