吉林永吉地区南楼山组火山岩锆石U-Pb年代学及地球化学特征  

Zircon U-Pb Chronological and Geochemical Characteristics of Volcanic Rocks from the Nanloushan Formation in Yongji Area,Jilin Province

作　　者：韩作振[1,2] 闫俊磊 刘辉 宋志刚[1,2] 韩梅 钟文建[1,2] 李晶晶 

机构地区：[1]山东科技大学山东省沉积成矿作用与沉积矿产重点实验室,山东青岛266590 [2]山东科技大学地球科学与工程学院,山东青岛266590

出　　处：《山东科技大学学报（自然科学版）》2018年第1期10-19,34,共11页Journal of Shandong University of Science and Technology(Natural Science)

基　　金：国家自然科学基金项目(41372108);高等学校博士学科点专项科研基金项目(20133718130001);山东科技大学科研创新团队支持计划资助(2015TDJH101)

摘　　要：通过对吉林永吉地区南楼山组玄武安山质凝灰岩中锆石阴极发光图像分析,锆石晶形较好,内部结构比较清晰,具有中基性岩典型的板状环带,且Th/U比值较高,介于0.73~1.52,反映了其岩浆成因的特点。LA-ICPMS U-Pb测年结果显示,12个测点的^(206)Pb/^(238)U加权平均年龄为176.6±3.8 Ma,表明玄武安山质凝灰岩的形成时代为早—中侏罗世。地球化学分析结果显示,玄武安山质凝灰岩中相对富集轻稀土元素和大离子亲石元素,而相对亏损重稀土元素和高场强元素,反映了岛弧或活动大陆边缘火山岩的特点;在Th-Ta-Hf/3三角图和Th/YbTa/Yb构造环境判别图中,投点集中在陆缘弧型钙碱性火山岩区,揭示其形成于与大洋俯冲作用相关的构造背景,结合区域构造演化,其形成于古太平洋板块向欧亚板块俯冲背景下。This paper analyzed the zircon U-Pb chronological and geochemical characteristics of volcanic rocks from the Nanloushan Formation in Yongji area,Jilin Province.The CL images of zircons from the basaltic-andestic tuffs show that the zircons are in good shapes with clear internal structures,typical magma concussion growth zoning,and high Th/U ratios(0.73-1.52),indicating a magmatic origin.LA-ICP-MS U-Pb dating results show that the weighted mean age of the 12 measured points of ^(206)Pb/^(238)U is 176±3.8 Ma,indicating that the formation age of the basaltic-andestic tuffs was Early-Middle Jurassic.Geochemical analyses show that the basaltic-andestic tuffs are richin LREEs and LILEs but poor in HSFEs,indicating characteristics of island arc or active continental margin volcanic rocks.The plotted points concentrate within the continental arc calc-alkaline volcanic rocks field in the Th-Ta-Hf/3 tectonic discrimination diagrams and the Th/Yb-Ta/Yb triangular diagram,indicating that they were formed in a subduction-related tectonic setting.Combined with regional tectonic evolution,this paper suggests that the basalticandestic tuffs were formed in the background of local tension setting that related to the subduction of the PaleoPacific Oceanic Plate to the Eurasian Continental plate.

关 键 词：早-中侏罗世 玄武安山质凝灰岩 锆石U-PB定年 地球化学 古太平洋 

分 类 号：P588.14[天文地球—岩石学]